The ecology and behavior of the California moray eel Gymnothorax mordax (Ayres, 1859) with descriptions of its larva and the leptocephali of some other east Pacific muraenidae

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Content THE ECOLOGY AND BEHAVIOR OP THE CALIFORNIA MORAY EEL GYMNOTHORAX MORDAX (AYRES, 1859) WITH DESCRIPTIONS OP ITS LARVA AND THE LEPTOCEPHALI OF SOME OTHER EAST PACIFIC MURAENIDAE by Kim McCleneghan A Dissertation Presented to the FACULTY OF THE GRADUATE SCHOOL UNIVERSITY OP SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY (Biology) June 1973 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. UNIVERSITY O F SO U T H E R N CALIFO RN IA TH E G R A D U A T E S C H O O L . U NIVER SITY P A R K L O S A N G E L E S . CA LIFO RN IA 90007 T h is dissertation, w ritte n by ................ Kim .-MaCleneghaii......................... under the direction of his... D issertation C om m ittee, and approved by a ll its members, has been presented to and accepted by T h e G raduate School, in p a rtia l fu lfillm e n t o f requirem ents o f the degree o f D O C T O R O F P H I L O S O P H Y DISSERTATION COMMITTEE St., r i ? . S . ^-----\ V Cha Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ACKNOWLEDGEMENTS I would like to express my appreciation to the Allan Hancock Foundation and the Santa Catalina Marine Biological Laboratory for providing research facilities and financial support throughout this investigation. Two Biomedical Sciences Support grants from the National Institutes of Health also provided equipment and materials. Special thanks go to Dr. Gerald J. Bakus, Chairman of the Dissertation Committee, and Dr. Russel L. Zimmer, Resident Director of SCMBL and a Committee member, for their able assistance. Other Committee members, Drs. Basil G. Nafpaktitis, Jay M. Savage, John S. Garth, and Donn S. Gorsline were generous with both time and equipment. I wish also to acknowledge the ingenuity and capability of Mr. Lawrence Loper, SCMBL, and to thank him for the many hours of construction time necessary to build various devices used in conjunction with this research. Many graduate students at the University of Southern Cal ifornia discussed and assisted with various aspects of the investigation. This aid and their friendship is appre ciated. IHy wife Muffet, capable of tending boats and air hoses as well as typing the manuscript and its revisions, ii Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. was of considerable help during this study. iii Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF CONTENTS Page ACKNOWLEDGEMENTS ............................ ii LIST OF TABLES............................. vii LIST OF FIGURES. ................... ix Chapter I. INTRODUCTION........................ 1 II. GEOGRAPHICAL DISTRIBUTION OF EAST PACIFIC MURAENIDAE ............. 6 III. ECOLOGICAL AND BIOLOGICAL OBSERVATIONS OF GYMNOTHORAX MORDAX (AYRES, 1859). . . ......... 15 Habitat......... 15 Tagging.......................... 16 Introduction Methods and materials Results Discussion Population Density............... 39 Introduction Methods and materials Results Discussion Activity............... 53 Introduction Methods and materials Results Discussion Food and Feeding................. 76 Introduction Methods and materials Results Discussion iv Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Page Length-Weight Relationship. ... 93 Introduction Methods and materials Results Discussion Age................................ 101 Introduction Methods and materials Results Discussion Reproduction. . .............. 105 Introduction Methods and materials Results Discussion IV. SEA WATER CIRCULATION OFF THE COAST OF SOUTHERN CALIFORNIA AND BAJA CALIFORNIA.................. 114 V. DESCRIPTIONS OF SOME MURAENID LEPTOCEPHALI FROM THE EASTERN PACIFIC .................. 118 Introduction.................... 118 Characteristics of Adults and Larvae of Eastern Pacific Muraenidae. .............. 119 Collections................. . 126 Methods and Materials .......... 126 The Leptocephalus of Oymnothorax dovii (Gunther. 18?0).......... 127 Material examined Description Discussion The Leptocephalus of Gymnothorax mordax (Ayres* 1859)............ 1^3 Material examined Description Discussion v Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Page A Leptocephalus Tentatively Identified as Gymnothorax Pictus (Ahl, 1769). . . ........ 157 Material examined Description Discussion The Leptocephalus of Gymnothorax weineri Sauvage, I883............ 165 Material examined Description Discussion An Unidentified Gymnothorax Larva (117 Myomeres). . . . . . . • 175 Material examined Description Discussion Ten Large, Unidentified Gymnothorax Larvae (167-176 Myomeres) , . . . . 185 Material examined Description Discussion Leptocephalus accipiter Fowler, 1936c . , . . . • ............ 199 Leptocephalus subfuscus Fowler, 1944. . . ................. 201 VI. SUMMARY AND CONCLUSIONS.............. 204- LITERATURE CITED.................... 208 vi Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OP TABLES Table Page 1. Geographical distribution of east Pacific Muraenidae ....... 7 2. Tagging results of Gymnothorax mordax recaptured and reobserved .............. 30 3. Individual diver counts of Gymnothorax mordax at each of seven census areas ................. 42 4. Averaged percentage of activity for each hour of the day over the 45- day activity study period, based on the total number of activity spikes • 71 5. Stomach content analysis of Gymnothorax mordax. including food ingested while eels and prey were confined in a trap ................... » 79 6. Food of Gymnothorax mordax in the natural environment . ............ 81 7« Vertebral counts of adult eels and myomere counts of described lepto- cephali for some species of eastern Pacific Muraenidae........... . 120 8. Vertebral counts of specimens of Gymnothorax •panamensis ....... 122 9. Collection data for larvae of Gymnothorax dovii ... ............ 130 10. Measurements of the leptocephali of Gymnothorax dovii .......... .... 132 11. Meristic counts of the leptocephali of Gymnothorax dovii 136 vii Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table Page 12. Measurements of the leptocephalus of Gymnothorax mordax................ 146 13. Meristic counts of the leptocephalus of Gymnothorax mordax • .............. 148 14. Measurements of that leptocephalus tentatively identified as Gymnothorax rictus .......... 160 15. Meristic counts of that leptocephalus tentatively identified as Gymnothorax rictus ....... . .. 162 16. Measurements of the leptocephali of Gymnothorax weineri.......... 168 17. Meristic counts of the leptocephali of Gymnothorax weineri. • ......... . 170 18. Measurements of an unidentified Gymno thorax larva (117 myomeres). ..... 178 19. Meristic data for the unidentified Gymno thorax larva (117 myomeres).......... 180 20. Collection data for specimens of an unidentified species of Gymnothorax larvae with 267-176 myomeres ........ 188 21. Measurements of the leptocephali of an unidentified species of Gymnothorax (167-176 myomeres) ..... ........ 190 22. Meristic counts of the leptocephali of an unidentified species of Gymnothorax (167-176 myomeres) .. ........ 193 viii Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OP FIGURES Figure Page 1. Areas (stippled) in Big Fisherman Cove, Santa Catalina Island, from which specimens of Gymnothorax mordax were trapped for a tagging study......... 18 2A, Stock tag . .............. 21 2BS Modified tag.......... 21 3. Tagging gun with modified tag in posi tion................................ 24 4, Unmodified tag inserted near the origin of the dorsal fin on Gymnothorax mordax................. 27 5, Relationship between total length (cm) and weight (kg) for males and females ^ 6, One-half inch conduit showing end with machined brass plug and axle........ 57 7, Cutaway diagram of pool with activity- monitoring device in place.......... 59 8, Cam design used on activity-monitoring apparatus ............. 62 9, Cam and switch in position, ......... 64 10, Circuitry used in conjunction with Esterline-Angus chart recorder to monitor moray eel activity, . , • • . 66 11. Recorded activity of Gymnothorax mordax. ......... .......... 69 ix Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure Page 12. Relationship between total length (mm) and weighty(gms) for ^ 13. Relationship between total length (mm) and weight (gms) for Gymnothorax mordax females............ 97 14. Two rectilinear regression lines show ing the relationship between total length (mm) and weight (gms) in male Gymnothorax mordax. .... ........ 102 15. The leptocephalus of Gymnothorax dovii . • • • •• • •• • .......... 128 16. The leptocephalus of Gymnothorax mordax. .. . ........ 144 17. A leptocephalus tentatively identified as Gymnothorax pictus .............. 1$8 18. The leptocephalus of Gymnothorax weineri ...••••• ............ 166 19. An unidentified Gymnothorax larva (117 myomeres). 176 20. A large unidentified Gymnothorax larva (173 myomeres), .... .... 186 x Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER I INTRODUCTION A small number of specialized groups within the Teleostei, but bearing little resemblance to most others of that group* diverged from the mainstream of teleostean evolution during the late Mesozoic. One of these was the eel-like fishes. Order Anguilliformes. Castle (1968) reported that in this order there are at least 100 genera and over 300 species currently known. Characteristically these fishes are elongate with vertebrae usually numbering from 100-200, though some may have as many as 500-600. Besides the body form, these fishes also possess a trans parent, eel-like larva, or leptocephalus. Several of the families in this order are more com monly known than the others. The Anguillidae are fresh water eels that return to the sea to spawn. The Conger eels (Congidae), snake eels (Ophichthidae), and moray eels (Muraenidae) are marine and account for the majority of eel genera and species. The latter two are primarily distributed in tropical regions. Moray eels, though generally inhabiting rocky areas in shallow water or coral reefs along mainland coasts or 1 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2 oceanic islands, have been neglected by most investigators conducting research on marine fishes. Most likely their fearsome appearance has dismayed many who have contemplated a study involving these animals. Personal observations, as well as those made by Hoglund (1964) and Randall (1969). suggest that the moray is worthy of respect but should not be unduly feared. However, there are records of attack on divers, some quite vicious, but almost all of these have been provoked in some manner (Halstead, 19591 Gosline and Brock, i9601 Randall, 1969). Most of the non-taxonomic work done on the Muraen- idae to the present has been in conjunction with studies of other fishes. Those studies conducted specifically on morays have most often dealt with feeding or related as pects of their behavior and morphology. Though relatively little has been done on the biology of these fishes, there remains much to be done on the taxonomy as well. Currently there are over 100 described species of Muraenidae (Eldred, 1969b), with new additions being made to this number almost annually. However, though many adults are known, very few have had their leptocephalus larva recog nized and described. Presently there are only approxi mately twenty larval forms identified with the adult species. This is due to the fact that leptocephali possess few, if any, characters to correlate it with the parental form. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 3 After spawning, the buoyant eggs of morays probably develop in near-surface waters, where hatching also most likely occurs. The larva, a few millimeters in length at first, is a planktonic organism drifting with the ocean currents. Development and growth in the leptocephalus of muraenids is estimated to take up to a year (Castle, 1965). At the completion of growth, with a total length (TL) of from 50 to 165 mm depending on the species, and under the influence of a stimulus or stimuli as yet unde termined, the larva begins to undergo metamorphosis. Dur ing metamorphosis the larva gradually assumes the appear ance of the juvenile of its species by becoming shorter in length and developing surface pigment. The body becomes rounded in cross section, and the larval teeth are lost, only to be replaced by adult-type dentition. Familial and generic characters are fairly well established for a number of forms. It has been shown that various structural characters (e.g. total number of myomeres, number of pre- and post-dorsal and pre- and post-anal myomeres, etc.) and the distribution of melanophores are important for the recognition of genera as well as species within a family group. Additionally, the number of myo meres, or muscle segments, in the larva and the number of vertebrae in the adult correspond, though there is a range of variation in this number. Factors such as temperature and salinity affect the vertebral number in Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 4 developing fish (Hoar and Randall, 1969). Though the vertebral count is a useful character in attempting to identify a leptocephalus, care must be taken as more than one species in the same region may have similar numbers of vertebrae. At present there are several investigators around the world involved in taxonomic studies on eels and lepto cephali. Castle works on eels, especially their larvae, from the Indo-Pacific and has published extensively regarding leptocephali. Blache has been investigating the eel populations and leptocephali occurring in the eastern Atlantic, and Eldred has described the leptocephali of some Caribbean eels, McCosker has been conducting taxonomic studies of east Pacific Anguilliformes, espe cially the Ophichthidae, but until now no one has worked on the east Pacific leptocephali. A decision was made to investigate the biology and life history of a lone species of the Muraenidae which occurs in the waters of Southern California. Of those muraenids which occur in the east Pacific, the California moray eel, Gymnothorax mordax (Ayres), is the sole representative occurring commonly in the temperate zone north of Magdalena Bay, Baja California. South of this area in tropical waters and in the Gulf of California there occur 26 other muraenids with varying geographical distributions, many of which overlap to some extent. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. It was hoped that the presence of a single moray species off Southern California would facilitate the study of this eel's life history. However, this was not the case. Nevertheless, certain aspects of its biology were elucidated. A larva believed to be that of G. mordax is described, but other details of its life history remain uncertain. Also included are those leptocephali thought to belong to various other species of Gymnothorax that occur along the west coast of the Americas. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER II GEOGRAPHICAL DISTRIBUTION OF EAST PACIFIC MURAENIDAE The moray eel family, Muraenidae, comprises a large number of species. Most morays are tropical in distribu tion and particularly characteristic of coral reefs. Many fishes besides muraenids are highly diverse in tropical latitudes, and this diversity is probably directly related to the complexity and porosity of the coral reef struc tures (Bakus, 19691 Rosenblatt, McCosker, and Rubinoff, 1972). By far the greatest diversity of muraenids occurs in the Indo-west Pacific where there are more than 4-00 species. Ten (37#) of the 27 morays currently described from the west coast of the Americas are also Indo- Pacific (Table 1). All of these Indo-Pacific representa tives occur in the Panamic faunal province within the 20°C isotherm, by definition the latitudinal boundary for tropical organisms (Briggs, 196I1 Castle, 1968). In the eastern Pacific the 20°C isotherm extends from Magdalena Bay, Baja California, to Cape Aguja, Peru. Recent work by Rosenblatt et al. (1972) has shown that most of the morays of Indo-west Pacific origin occur along the 6 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 1 Geographical distribution of east Pacific Muraenidae. * denotes endemic species. 7 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 8 OCt i ^ CDi HOOCGOCt i © W f f i O l S O O O P - i p r J O P - . *Anarchias salapag:ensis X X X Echidna nebulosa X X X X X *Echidna nocturna X X X X X X X' X Echidna zebra X X X X X *Enchelycore octavianus X X X Enchelynassa canina X X Gymnothorax buroensis X X X X ^Gymnothorax castaneus X X X *Gymnothorax dovii X X X X X X X Gymnothorax eurostus X Gymnothorax flavimar^inatus X X X X *Gymnothorax mordax X X Gymnothorax panamensis X X X X X X Gymnothorax pictus X Gymnothorax undulatus X X *Gymnothorax weineri X Gymnothorax sp. X Gymnothorax sp. X X X *Muraena argus X X X X *Muraena clepsydra X X X X X X *Muraena lentiginosa X X X X X X *Priodonophis angusticeps X *Priodonophis equatorialis X X X *Uropterygius necturus X X X X X X *Uropterygius polystictus X *Uropterygius schultzi X X X Uropterygius tigrinus X X X Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. American mainland rather than being restricted to the oceanic Revillagigedo, Cocos, Clipperton, and Galapagos Islands as previously reported. Of these Indo-west Pacific representatives only Gymnothorax pictus remains to be collected along the mainland coast. Fifteen muraenid species, or $6% of the total number of east Pacific morays, are endemic to the east Pacific (Table 1). Of these, two occur in temperate latitides, with one in each hemisphere. Gymnothorax mordax (Ayres) is found to the north of Magdalena Bay, Baja California, and G. weineri Sauvage has been collected at Lobos de Afuera Islands, Peru. Two additional species are known only from their larvae, which are described in a subsequent section. It is possible that either one or both of these may be known Indo-west Pacific species or new species endemic to the east Pacific muraenid fauna. Emerson (1967) reported that near the end of the Mesozoic Era, restriction and eventual blocking of the Tethyan Sea also divided the circumtropical marine fauna into faunal provinces. During the Tertiary, Caribbean hermatypic corals flourished, whereas reef development along the western Americas was significantly diminished. Cosmopolitan coral reef-associated organisms continued successfully in the tropical western Atlantic, but despite sea water connections between the Caribbean and tropical Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. eastern Pacific that lasted until about five-million years ago (National Academy of Sciences - National Research Council, Division of Biology and Agriculture, Washington, D.C*, 1970), the latter region lacks many species that are characteristic of the coral atolls of the present Indo-west Pacific fauna (Emerson, 1967). He suggested this may be due to the relatively poor development of coral reefs in the eastern Pacific, though Rosenblatt et al. (1972) found well-developed hermatypic coral reefs in the Gulf of Chiriqui, Panama, with of the total fish population of Indo-Pacific origin. Nevertheless, Rosenblatt and Walker (1963) reported that though there is a high degree of endemism in the fish fauna of the eastern tropical Pacific, the relationships of these lie primarily with the western Atlantic fauna, the differences being due to faunal differentiation (representing a change of 80-9836 as reported in 1970 by the National Academy of Sciences) since the closing of the sea connec tion, and to limited dispersal into the eastern Pacific by Indo-west Pacific species. The tropical west Atlantic extends from 35° N to 35° S, whereas the limits of the tropical eastern Pacific lie at 25° N and 5° S. This marked narrowing of the trop ical habitats in the seas off the western Americas is a consequence of continental configuration and current pat terns (Hubbs and Rosenblatt, 196I1 Rosenblatt and Walker, Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1963)* The strong, cold, surface currents, the California and Peru currents, effectively reduce the extent and rich ness of the tropical marine fauna in the eastern Pacific. As these two currents flow towards the equator, they are deflected westward to become the North and South Equato rial Currents. These two Equatorial Currents, warmed during their westward movement, spread out towards the higher latitudes in the central and west Pacific and sup port the development of a vast region of coral reefs and an associated, highly diverse fauna. In comparison to the Indo-Pacific coral reefs, the coral development and faunal diversity of the eastern Pacific are relatively modest. This condition suggests that the two regions have long been separated by a rela tively impassible obstacle. Briggs (1961, 1964) developed and elaborated an earlier suggestion made by Ekman (1953) that the wide expanse of open ocean with very few islands westward from tropical American shores acts as a barrier to the dispersal of most fishes. It was proposed that this "East Pacific Barrier" was responsible for the pronounced break in the circumtropical shore fauna. However, the several equatorial currents provide the potential means of traversing this barrier. Examination by Hubbs and Rosenblatt (1961), Walker (1961), Rosenblatt and Walker (1963), Emerson (1967), Briggs (1970), and Rosenblatt et (1972) indicates that faunal dispersion has been Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. primarily from west to east, the opposite direction of flow for the major equatorial currents. The cold Cali fornia and Peru Currents, whose waters form parts of the westward-flowing North and South Equatorial Currents, have been effective in minimizing the dispersal of trop ical east Pacific faunal elements into the Indo-west Pacific. The Equatorial Countercurrent seems to be responsible for the transport of Indo-west Pacific species to the tropical Pacific offshore islands and coastal waters (Hubbs and Rosenblatt, 1961). It was also sug gested by them that this current, rather than the deep, eastward-flowing Cromwell Current, was responsible for the dispersal, because those Indo-west Pacific faunal elements that have become established in the New World generally have a long-lived, surface-swimming larval stage(s). Additionally, these same species were most numerous on those offshore islands in the path of the countercurrent, i.e., Clipperton, Cocos, and Revilla- gigedos Islands, and less common on the Galapagos Islands and the mainland. These observations led them to postu late several reasons for the effectiveness of west to east dispersal and ineffectiveness of east to west dispersal. They suggested that a major reason for this phenomenon was the relative faunal saturation in the Indo-west Pacific and the depauperate condition in the east Pacific. They also suggested that the Indo-west Pacific fauna was Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. better adapted to island life, being less restricted to continental shelf habitats and more adapted to oceanic dispersal. Even so, evidence shows the marked eastward faunal attenuation of tropical west Pacific forms (Emerson, 1967). He suggested that poor coral reef development in the eastern Pacific may also be an impor tant factor in limiting the diversity of the Panamic mol- luscan fauna. Rosenblatt et al. (1972) noted that this may also hold true for corallophillic fishes, and that the presence of suitable coral reef habitats may be respon sible for the success of Indo-west Pacific fishes in the Gulf of Chiriqui, Panama. With respect to fishes, the Muraenidae are repre sented by a greater number of dispersed species from the west to east Pacific (37# or 10 species) than any other family. This is not surprising for morays possess a leptocephalus larva, a planktonic developmental stage that exists for many months before undergoing metamorphosis to the adult form. Such a larva would be more capable of crossing the East Pacific Barrier than those species of fishes lacking a long-lived planktonic larval stage. Also, the porous nature of a coral reef can be readily exploited by these fishes. Considering that fewer than 10# (10 species) of the Indo-west Pacific muraenids are presently found along the west coast of the Americas, the difficulty encountered in successfully completing this Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. eastward dispersal is apparent even in those fishes pos sessing a larval form conducive to transport by ocean currents• Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER III ECOLOGICAL AND BIOLOGICAL OBSERVATIONS OF GYMNOTHORAX MORDAX (AYRES, 1859) Habitat Moray eels seem to prefer the holes, cracks, and crevices of either rock or coral reefs as refuges (Gos- line and Brock, 19651 Bohlke and Chaplin, 1968* personal observation). The California moray eel, Gymnothorax mordax, is no exception. This moray is particularly abundant in areas such as submerged talus slopes where large rocks, fallen from weathering cliffs above surface, have produced an ideal habitat. The coasts of both Southern and Baja California and their respective off shore islands with numerous steep cliffs down to the water's edge provide many favorable sites for this speeiea Fitch and Lavenberg (1971) reported that the moray can be found to depths of 40 m if the proper habitat for them exists at that depth. However, I do not recall observing one below a depth of 25 m in the waters off Santa Catalina Island even though I logged about 100 hours of diving time below this depth during a three-year stay there. Generally, small eels are found concealed 15 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 16 among the cobbles in very shallow, near-shore water, while the larger morays occur in deeper water among the rocks and bowlders. Prom personal observation it is estimated that 95# of the eel "population around Santa Catalina Island inhabits water less than 15 m in depth. Although one commonly sees morays crowded into shelters provided at the various marine aquaria (Marine land of the Pacific, Sea World, and Scripps Aquarium), they behave differently in nature. Commonly one observes a solitary moray occupying a small rocky cave in the reef. Occasionally two eels occur in very close proxim ity to one another, concealing themselves in two adjacent holes. The eel population was usually well dispersed over the reef, and territorial defense was never observed. Only when food was introduced into the immediate area did the eels become agitated, and in searching the reef for the source of the "scent", they would often crowd into a cave where one or more eels might already be present. The morays often protrude the anterior half of their bodies out of the hole in an-apparent attempt to locate the food. This behavior was used advantageously to esti mate the density of naturally occurring populations. Tagging Introduction While conducting an investigation of the biology of Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 17 the California moray eel, Gymnothorax mordax, at the University of Southern California Santa Catalina Marine Biological Laboratory (SCMBL), a study of natural moray eel populations was proposed as an integral aspect of that research. Tagging and recapturing of individuals was the method chosen to obtain the data required to evaluate aspects of population dynamics. Big Fisherman Cove, adjacent to SCMBL, was chosen as the study site. Collec tions of eels for tagging were made from those areas indicated in Figure 1. However, the moray eel presents unique problems not encountered in most fish-tagging programs. Gymnothorax mordax habitually conceals itself in the cracks, crevices and caves of submerged rocky reefs. Much of the eels' dirunal and nocturnal activity takes place in a habitat that subjects a tag to severe abrasion. Therefore, of primary consideration in choos ing a tag was that it not be susceptible to snagging among the rocks and thus be torn from the fish. The tag must also identify the individual in order that growth data can be collected on recapture, and it must be observable and its numerals discernable by a scuba diver so that movements might be detected as well. Commercially available "spaghetti" tags capable of withstanding abrasion and not prone to snagging were too expensive for the limited budget. Furthermore, these tags could not be sequentially numbered and thus would not provide a means Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 1. Areas (stippled) in Big Fisherman Cove. Santa Catalina Island, from which specimens of Gvmnothorax mordax were trapped for a tagging study. 18 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 19 Pier Ramp 30 m Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 20 of individual recognition. These facts necessitated the development of a new, individualized, low-cost tag. Methods and materials A yellow 6.5 cm long "flag" type plastic anchor tag (Fig. 2A) was chosen (available from Floy Tag and Manufacturing, Inc., Seattle, Washington, catalog no. FD-67F). The factory-style rectangular flag was trimmed to a semicircular shape (Fig, 2B) using a #3 cork borer with a notch filed in the cutting edge. This notch, when placed over the monofilament, allowed the flag to be trimmed in a single operation without cutting the mono filament streamer. The purpose of this procedure was to reduce the size of the flag, thereby minimizing the hazard of the tag becoming snagged and consequently pulled out of the flesh. Each tag was sequentially numbered using small printed numerals attached tothe flag with "E Pox E" Epoxy cement. Each flag was roughened with a hot needle prior to the application of the epoxy. A drop of cement was then applied over the surface of the flag, the numeral posi tioned, and a final drop of cement allowed to cover the numeral. The flag was placed in a horizontal position so that the epoxy would not drip. Drying was hastened by placing the tags in a covered slide warmer at 50°C for 24 hours. A Rapidograph pen filled with India ink could also Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 2A. Stock tag. B. Modified tag. 21 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. < U_ cr x o Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 23 be used to number the tags. The perimeter of the flag should then be roughened for better adhesion of the cement. If underwater observations are required, both sides of the flag should be numbered and epoxyed. A 30 cc disposable syringe with a 10 cm long, 15-gauge needle was modified for use as a tagging gun. The needle point was filed so the anchor of the tag could be slipped within the barrel of the needle (Fig. 3). The rear edge of the filed groove was examined to make certain that it was not sharp enough to damage the monofilament when the needle was inserted into the flesh. A wire with a diameter slightly smaller than the inside diameter of the needle, passed through the needle and the plunger’s center, completed the tagging device. With the plunger fully depressed, the wire should extend at least 0.5 cm beyond the tip of the needle in order to insure release of the anchor. The tagging gun was loaded by drawing back the plunger and slipping the anchor into the slotted needle. To properly set a tag in an animal, the needle was allowed to penetrate the skin beyond the slot. After insertion of the needle beneath the skin, the plunger was depressed, causing the wire within the needle to extrude the anchor into the flesh. After withdrawing the needle, a slight tug on the tag determined if the anchor had been correctly set. Sincerunderwater observation was a prerequisite to Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 3« Tagging gun with modified tag in position. 24 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Ink Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1 CM 26 choosing a suitable tagging site on the body of the moray, it was decided that near the origin of the dorsal fin was the most advantageous location (Fig, 4). To hold an eel during the tagging operation, a V-shaped trough 1,25 m in length with 10 cm sides was constructed. It was important to wet the trough thoroughly before placing an eel in it, because they became violent when placed in a dry trough. However, eels remained relatively motionless when placed in a thoroughly wetted trough, A flat board 10 cm wide and 1 m long with a handle was used as a cover to posi tion the eel and hold it in place for tagging. For small specimens a piece of dense synthetic sponge 2.5 cm thick placed directly behind the tag site and beneath the eel facilitated needle insertion. The cost of materials to produce the described individualized tag and tagging gun was low ($7,00 for 1000 tags and $1,00 for the gun), and therein lies the advantage of this system over many others. However, since time is required for the preparation of each tag, it may not be suitable for large-scale tagging operations. Results Of the 116 eels tagged over a six-month period, only six were retrapped. An additional eight were ob served while diving, though one was missing the flag por tion of the tag and so is not listed in the following Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure U, Unmodified tag inserted near the origin of the dorsal fin on Gymnothorax mordax. Needle of tagging device is also shown* 2? Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 29 table. Table 2 presents the number of days at large and distance from the original collection site for both recaptured individuals and those observed while diving. Discussion Southwood (1968) discusses various methods of esti mating populations* including absolute estimates (density/ unit area)* relative estimates (density through time), and population indices (animal products, rather than animals counted). Common to both absolute and relative estimates are trapping and marking techniques. Using these methods and the results of the eel tagging study, an attempt was made to estimate the eel population of Big Fisherman Cove, Santa Catalina Island. Various assumptions underlie all capture-reeapture methods of estimating populations. Southwood (1968* p.75) recorded the following assumptions common to most methods of analysis 1 1. The animal is not affected by the mark or tag. 2. The marks or tags are not lost. 3. The marked animals become completely mixed with others of their species. 4. The population must be sampled randomly with age groups and sexes equally liable to collec tion. 5. Sampling time must be short in comparison to Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 2. Tagging results of Gymnothorax mordax recaptured and reobserved. 30 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 31 Tag no. Total length Days at (mm) large Distance moved (m) 52 1045 1 0 25 756 5 23 110 959 21 15 80 742 50 15 59 685 52 77 65 1041 96 62 108 1100 6 3 113 8?8 6 3 110 955 6 23 47 853 7 15 26 856 11 8 6 1055 33 1 38 702 79 108 ‘Reotserved Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 32 total time. 6. The population must be closed or, if immigra tion and emigration are occurring, it must be measurable. 7. Ideally there should be no births or deaths during the sampling period, but this must be allowed for if they do occur. 8. Recapture of an animal must not be affected by its previous capture. 9. Capture-recapture techniques cannot be applied to populations whose members are concealed by the habitat, thereby allowing only part of that population to be sampled. The tagging study conducted on the G. mordax popu lation within Big Fisherman Cove, Santa Catalina Island, did not meet the above conditions in several important respects. Because this fish habitually swims- among the small caves of rocky reefs, the tag is subject to snagging and heavy abrasion. The unmodified tag style used ini tially (p. 20 and Fig. 2A) was more susceptible to this than the modified tag (Fig. 2B). Undoubtedly some tags were lost. One moray was observed in the field with the numeral-carrying flag missing from the monofilament. Secondly, not all age groups were collected. Eels less than 500 mm TL were rarely collected and seldom seen. Traps for small morays, using a variety of baits, were Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. largely unsuccessful. Third, it became apparent from diurnal and nocturnal diving observations that this was not a closed population. At nighttime during foraging activity these eels swim about the rocky subtidal in search of food. Fourth, though the life history of this moray is still incomplete, it is probable that no births occurred in the vicinity. Moreover, the number of deaths remains indeterminable. Finally, these eels occupy a habitat whose features allow only partial sampling of the population. These problems prevented absolute population estimates from being made. More direct methods had to be utilized in order to obtain an estimation of the population density. Nevertheless, the tagging of these eels did pro vide other insights into their behavior. Southwood (1968) reported that a 5# return of pre viously tagged animals is average, though various factors concerning the longevity of the animals and tag may result in either higher or lower recovery percentages. The moray tagging study produced a 5% recapture in traps and by observations in their natural habitat. Though these latter eels were noted while diving, this record gives no informa tion on their growth. Changes in length and weight between successive trappings for tagged eels were not always positive. Those eels at large from 1 to 21 days showed from -5 mm to +4 mm change in total length and from -60 gm to +61 gm change in Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. weight. The length fluctuations are most likely due to the eel's capability of shortening its length by contrac tion of its muscles. Observation of this phenomenon showed that an eel could reduce its length by about 1 cm when contracting, more if it flexed the vertebral column. Attempts were made to have the eel as relaxed as possible before measuring, but these were not always successful. This problem is probably restricted to eel-like fishes, as the morphology of most other teleosts prevents this con traction and thereby permits reproduceable measurements. The differences in weight are undoubtedly due to food either present or absent in the gut at the time of weight determination. Such fluctuations in length and weight can only be minimized by successive recaptures after a greater number of days at large. Those eels retrapped from 50, 52, and 96 days after tagging showed 0 mm, 7 mm, and 13 mm increase in total length, respectively. The first eel had lost weight, but the latter two had gained 63 gms and 335 gms in that order. Computing the growth of eel #59 with 7 mm increase in TL and 69 gm increase in weight, one finds that, at this rate, it would grow 50 mm and add 441 gms annually. Moray #65, at large 96 days, grew 13 mm and added 335 gms to its initial measurements. Calculating this, one finds its annual growth would be 52 mm and 1340 gms. Though the annual increase in length is similar for both, the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 35 weights are markedly different. It is possible that the latter tagged moray had a large amount of food in the gut, thereby distorting the actual weight increase figure. Inspection of otoliths indicated that eels between 600 mm and 700 mm TL belonged to one age class, whereas eels from 700 mm to 800 mm TL were a year older. The annual weight increase in the 700-800 mm range is in the vicinity of 500 gms.as indicated by the length-weight graph (Pig. 5). Comparing observed and calculated annual increases of these parameters, one finds that the 50 mm and 441 gm calculated growth for eel #59 compares favor ably with that range predicted from the graph. Observations by a number of scuba divers (personal communications) have indicated that some California morays appear to occupy their particular cave over a long period of time. That some species of morays have a home range is established. Dr. H. Heberlein (personal communication) observed a single individual of Muraena helena in the Mediterranean over a period of 5 years. He was able to train the eel to respond to underwater noises and come from some distance to be fed. He also produced a film and several popular articles of this moray*s behavior.. However, territorial behavior for G. mordax has not been established. Moreover, the results of this tagging study are also inconclusive. Table 2 lists those eels tagged and subsequently recaptured or observed in the field and Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 5. Relationship between total length (cm) and weight (kg) for males and females of Gymnothorax mordax. 36 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 37 (UID) ljl6ud-| Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Weight (kg) 38 the approximate distance each of these had moved from the site of initial capture. One cannot make the generaliza tion that the longer an eel was at large, the further away it was from the site of original capture. However, those three eels free for 52 or more days were located from 62 to 108 m away from the site in which they were first cap tured. Ten individuals were observed or recaptured within 23 m of the release area from one to fifty days after tagging. One G. mordax was found at almost the same site after 33 days. Calculating the mean distance moved per day for each length group, one finds the following* > 600 mm TL, 1.5 m/day» > 700 mm TL, 2.1 m/day (range 0.3-4.6 m)» > 800 mm TL, 1.1 m/day (range 0.5-2.1 m)» > 900 mm TL, 2.3 m/day (range 0.6-3.8 m)j > 1000 mm TL, 0.3 m/day (range 0.0-0.6 m). It is possible that the larger morays (> 1000 mm) estabxish territories (although this was not observed in the present study), while smaller ones are continually immigrating to and emigrating from any given region. Of 116 eels trapped and tagged in a small area of Big Fisherman Cove, Santa Catalina Island, 103 (8995 of the total), of which 77# were shorter than 1000 mm TL, were not seen again even though trapping and diving observations continued for over one-half year. Of the 13 eels recaptured or reobserved, 69# were shorter than 1000 mm TL. These results were inconclusive and further observations must be made to establish the presence Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 39 or absence of territorial behavior in eels longer than 1000 mm TL. If a home range is established by the larger eels, then these observations indicate that it covers a broad area of the reef. The moray of 10^1 mm TL, at large 96 days, was 62 m from the original tagging site. The number of recaptures of any individual moray was insuf ficient to calculate the size of the home range. A com plete tagging program involving all eels of various size ranges within a defined region is required to confirm or deny this hypothesis. This population should be observed frequently and sampled periodically over a period of six to twelve months in order to establish whether territori ality exists in this animal. Additional collections are suggested in order to determine the extent of the home range, if it exists. Population Density Introduction Brock (195*0 was one of the first to use scuba as a technique in estimating the numbers of fishes occurring over tropical reefs. Using diver-estimated length of each fish and previously compiled length-weight curves for each species, he was able to calculate the approximate standing crops of each fish species observed within the sampling area. Because absolute population estimates could not be computed using tagging-recapture techniques, it was Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 40 decided to use a modified form of the Brock (195*0 method. Methods and materials In order that the population density of the Califor nia moray eel be quantitatively described, a census was carried out by two divers. A bait solution, to be broad cast underwater by the divers, was prepared by grinding three Spanish mackerel, each weighing about 100 gms with 500 ml of sea water in a high speed Waring blender. This fish slurry was poured into a plastic bag, sealed with a wire tie, and placed in a bucket to be taken into the field. Counting was facilitated by "chumming" an area of reef and recording the number of heads that appeared shortly thereafter. An area along the north side of Big Fisherman Cove, Santa Catalina Island, was chosen for the census site. A fairly narrow (5 m) submerged talus slope extends from the back of the cove out to a cave, a distance of 91,5 m. This was divided into seven areas from which counts were made. Sand bottom breaks in an otherwise continuous rocky reef provided natural boundaries between the census area. This provided nearly an ideal site because these zones between suitable habitat areas reduced the possibility of eels swimming from one area to another, thereby distorting the population count. Moreover, this region has only sparse, small algae, with little giant kelp (Macrocystis), Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. so eels were not obscured by a dense flora. In the area in which eels were to be counted, one diver punctured the plastic bag containing the fish slurry and broadcast this over the region while slowly swimming around it. Care was taken not to stir up silt or sediment, thus reducing visibility (visibility underwater during the study was more than 8m). Eels began to protrude their heads out of the holes within less than a minute after broadcasting the slurry. Each diver cruised the area slow ly, but thoroughly, making independent counts at least several times. Each.area was surveyed from the intertidal to the reef sand interface, about 5 m at its greatest depth. Eels usually remained at or near the hole from which they first emerged, making repeated counts possible. When the divers had completed their survey, the numbers observed were recorded on an underwater writing slate. The same procedure was repeated at each of the other six stations. Results Table 3 presents individual diver counts in each census area. By calculating the mean population density from this information, one finds that there is one moray per 8.8 m2 of reef surface. This is probably a minimum density since some small eels could have been missed. In order to verify the accuracy of the initial Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 3. Individual diver counts of Gymnothorax mordax at each of seven census areas. 42 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 4 3 No. of eels counted per area Area no. Diver #1 Diver #2 1 6 2 2 3 5 3 14 12 4 6 8 5 7 7 6 5 5 7 12 12 Total 53 51 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. population survey, a second, even better-defined area was selected for a census. A rocky reef composed of large cobbles and boulders with attached, low-growing algae lay between the pier and boat launching ramp at Big Fish erman Cove. The area is roughly square, each side of which is 9 m in length and extends from the intertidal to a depth of 2 m. On the north and west sides the reef is bounded by broad expanses of open sandy bottom. On the south is a concrete launching ramp about 8 m wide which separates this rocky region from the remainder of the rocky subtidal along the back of the cove. The east side of the reef is shoreline. The same procedure previously described was used to attract eels from their holes and to count them. The same divers conducted this survey as well, and each counted nine eels in the area. Computing the population density for this quadrat gives a density of one eel per 9 m2. This figure compares favorably with that of the first study area. These figures are an indication of the minimum population density in rock piles of the type described. It should be expected that areas offering fewer places for concealment will have fewer morays. However, it is not surprising that large numbers of morays congregate in rock piles, for it is these same areas that support the diverse and abundant biota which serves as food for the many species of animals that inhabit the rocky subtidal. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. A third attempt was made to conduct a census, within a kelp bed near the head of the bay in Big Fisherman Cove. Methods of chumming and counting were performed as before using the same divers. In an area roughly 36 m2 nine morays were counted. However, this figure cannot be con sidered accurate because eels could enter the census area from adjoining regions. Moreover, thick kelp and dense algae covering the rocks made observing and count ing individuals exceptionally difficult. The resulting calculated density of one eel per 6 m2 probably reflects the recruitment of eels from adjacent areas into the study area while the census was being conducted. Con sidering the conditions under which the count was made, it is probable that some eels may have been counted more than once. In order to provide a rough estimate of the stand ing crop, the mean weight was calculated (1818 gms) using all the eels examined from Santa Catalina Island. The mean weight is undoubtedly high, as small morays (< 500 mm TL) could pass through the wire mesh of the trap used. Nevertheless, most morays observed during the census were at least 500 mm TL, and therefore it is assumed that the mean weight for the eels counted is similar to that of trapped eels. Considering the popula tion density to be one eel/9 m2, with each eel having a mean weight of 1818 gms, the calculated mean standing Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. crop of eels is 0.20 kg/m2. 46 Discussion Gosline and Brock (1965) reported a total of 32 eel species in 7 genera collected around the Hawaiian Islands, whereas Bohlke and Chaplin (1968) listed 10 species in 7 genera from the Bahamas. In the temperate sea off Southern California there is only a single species. This is presumably a more rigorous environment in regards to temperature limits for morays, since only one has successfully adapted to it. The differences between temperate and tropical diversity prompted a comparison of the population density and standing crop of fishes in these regions. Special attention was given to data re ported for the Muraenidae. Quast (1968) collected 2.87 kg of Gymnothorax mordax in an area of 4047 m2 (one acre) at Bathtub Rock, San Diego, California. This is equivalent to a standing crop of 0.0007 kg/m2. Unfortunately he did not report the number of eels in this collection thereby making impossible a population density calculation. It is probable, from interpretation of the kilograms collected and considering the generally large size of G. mordax. that the density of eels in the area was very low (~1 or 2/acre). However, Quast (19681 p. 73) described the substrate features at the collection site as "undercut boulders set in sand." Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 4 7 Personal observations have shown that eel densities in such habitats are very low. This would account for the discrepancy between our values of standing crop for G. mordax. More information compiled by various workers is available for tropical muraenid eels. In a poisoning station conducted at Kaena Point, Oahu, Hawaii, Hobson in 1959 (unpublished data) reported that 136 morays were col lected in an area roughly 25 m2. That is equivalent to a population density of one eel per 0.2 m2 and a standing crop of 0.24 kg/m2. Five species in 3 genera were represented in this collection. One hundred specimens were of a single species and 24 belonged to a second species. Only 24 specimens were greater than 300 mm TL, and all were less than 600 mm TL. In a poisoning station at a windward tide pool on Eniwetok Island, Eniwetok Atoll, Bussing (1972) collected 18 specimens of Gvmnothorax pictus and 2 of G. bikiniensis in an area of 800 m2. This is a population density of one eel/40 m2, far lower than that found by Hobson or me. Moreover, 18 G. pictus weighing 2357 gms, comprised about 44# of the total weight of fishes collected. Gvmnothorax bikiniensis accounted for another 73 gms. Using these data, the standing crop of eels in the 800 m2 tide pool was 0.003 kg/m2. That this was a supratidal pool is reflected in the calculated values for the population Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 48 density and standing crop of eels. Most likely these values would be significantly increased if subtidal areas could be adequately sampled. Randall (1963) made three subtidal quantitative collections of fishes in the Virgin Islands, Caribbean. At an artificial reef in Lameshur Bay he collected 7 morays in a 125 m2 area, or one eel per 17»9 m2. At a poisoning station along a portion of the fringing reef of Lameshur Bay, Randall collected 20 specimens in an area of 600 m2. o This represents a population density of one eel per 30 m . A third poisoning station on 297 m2 of the fringing reef at Ram Head Bay yielded 73 specimens or a density of one eel for each 4.1 m2. The standing crops of eels for these three stations were 0.0328 kg/m2, 0.0049 kg/m2, and 0.0048 kg/m2, respectively. It is generally accepted that diversity of fishes is greatest in the tropics. Additionally, many tropical species have moderate to high population densities (Bakus, 1969). This may reflect the tendency of mature communi ties or ecosystems to maximize biomass (Odum, 1969). Bardach (1959) and Bakus (1969) suggested that the stand ing crop of fishes in the shallow waters of coral reefs (<10 m) are higher than those of rock reefs in temperate latitudes. Temperate latitude standing crops may be greatest within the giant kelp (Macrocystis) habitat depths of 8-20 m (Bakus, 1969)* Brock (1954) found the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 49 standing crop of Hawaiian fishes to be 0.185 kg/m2, whereas a value of 0.049 kg/m2 was found for Bermuda (Bardach, 1959) and from 0.158 to 0.160 kg/m2 for the Virgin Islands (Randall, 1963). Quast (1968) reported that the average standing crop of fishes from Southern California kelp beds in water deeper than 8 m was 0.0288 kg/m2. Though these workers have determined the over-all standing crop of fishes to be higher in the tropics, it appears that this generalization may not hold when dealing with specific groups. Certainly the standing crop of G. mordax at Santa Catalina Island is comparable to that found by Hobson (1959) for Hawaii morays and higher than those standing crops of eels in the Caribbean and at Eniwetok. Though the total biomass of all rauraenids in the Kaena Point collection was similar to the Santa Cata lina Island collection, the standing crops of individual species were lower. These observations suggested that, where optimal habitats existed, the near-shore, benthic, top-predator, G. mordax. maximally utilized the resources available and for which there was no competition from other muraenids. This lack of competition^ among other things, in the temperate waters around Santa Catalina Island was probably a major factor in the high calculated biomass of G. mordax. Attempts to compare these and other data for popula tion densities and standing crops of fishes from both Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. temperate and tropical latitudes are difficult and hazard ous. Certainly many factors must be considered. Bakus (1969) suggested that the spatial heterogeneity of the coral reef structure and high primary production may be partially responsible for the higher standing crops of tropical, shallow-water fishes. However, temperate rocky reefs with their dense biotic growths must offer nearly the equivalent of the heterogeneity afforded by coral reefs. The problem of how to quantitatively describe these dif ferences in complexity remains to be solved. In future collections every effort should be made to accurately report the collection location, depth ranges, bottom types, major features, and conditions to which the area is exposed. These considerations must be taken into account in order to maximize comparability of data for population densities and standing crops from both tropical and temperate collec tions. It was noted earlier that the population density of the California moray at Santa Catalina Island approached those densities found in some tropical locations. The col lection made by Quast (1968) at San Diego, California, yielded far fewer eels per m2 than did the Santa Catalina Island survey. These previous studies indicate that con sideration must be given to potential collection sites. If specific fishes are desired, then attempts to collect these should be carried out in a variety of habitats. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Subsequent comparison of these stations would give a more accurate idea of the overall population density and stand ing crop of single species and the total fish population as well. Random tropical and temperate collections, though instructive as to the overall standing crop of fishes, are not highly profitable when used to study densities and standing crops of selected fishes. Additionally, most fish collections are not specifically made in order to capture muraenids. This group is notorious for its resis tance to fish poisons. These eels become quickly dis turbed in the presence of the poison and shortly after its detection often leave the area. Because of their tendency to swim among the caves and crevices of reefs, it is dif ficult to enclose an area and thus prevent their escape. Also morays are capable of squeezing through very re stricted places, which they commonly do. Consequently, even enclosing a subtidal area with a wall net may not preclude the escape of large numbers of eels. Perhaps these reasons are partially responsible for such large discrepancies between the densities and standing crops of eels reported by the various workers. Future collections for the purpose of obtaining quantitative information should take these points into consideration. The recycling of nutrients must also be considered when comparing temperate with tropical population densities and standing crops of fishes. In the lower latitudes this Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 52 recycling time is shorter as well as more efficient (Raymont, 1966). A high species diversity implies the presence of higher intensity inter-specific competition for either space or food resources or hoth. Such com petitive interaction results in the narrowing of the niche breadth, thereby reducing competition (Brown and Wilson, 1956i Rosenblatt, et al., 1972) . The tropical muraenids, as well as many other fish, are instructive in demonstrating that competition has had this result. Within the morays one finds that the various species differ in habitat type and depth, periods of activity, overall size, and dentition, to name a few. Behavioral and morphological differences, while decreasing competition among species, may put other constraints on a population. Reduction of niche breadth increases specialization. The result of the combination of relatively high species density with food niche specialization in shallow water tropical fishes of the equatorial Pacific is that they have had to tap to the maximum the resources available to them (Bakus, 1969). This is variously reflected in the diversity of predator- prey relationships! the high intensity of browsing, graz ing, sind predatiom and the morphological specializations for each of these feeding types. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 53 Activity Introduction Activity in Muraenidae is directly related to feed ing behavior. Most members of the genus G.vmnothorax are nocturnally active fishes (Bardach, Winn, and Menzel, 1959* Morris, 1959? Hiatt and Strasburg, I960; Starck and Davis, 1966} Bohlke and Chaplin, 1968). However, some shallow water Indo-Pacific and east Pacific species can be found swimming completely exposed over the reef flat searching for food during the day. Gymnothorax rictus is one of these (Chave and Randall, 1970). Another, G. flavimargin- atus, has been observed swimming during daylight hours by Bakus (personal communication) at Cocos Island off Costa Rica. Hobson (1968) reported that G. castaneus in the Gulf of California is also frequently observed exposed and away from cover during the day. He also reported that not only did G. castaneus leave its cover, but on one occasion was observed in midwater snapping at a school of larval fish. Some unusual and unexpected behavior has been observed by others as well. Bakus (1964) saw Gymno- thorax sp. pursuing Graosus grapsus over exposed rocky reefs in broad daylight at Fanning Island. Chave and Randall (1970) repor ted seeing G. pictus leave its cover and go so far as to jump out of the water in an attempt to pick grapsid crabs off a rock. They also observed the same species leaving the water in order to capture prey on Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 54 the beach. I have observed similar behavior of an uniden tified moray at Eniwetok Atoll. Both day and night diving observations have indi cated that the California moray, Gymnothorax mordax, is relatively inactive diurnally, but active nocturnally. During the daylight hours it remains secluded in holes, cracks, and crevices of rocky reefs. Often while occupy ing a hole, only the moray*s head is visible. However, just as frequently the moray is totally concealed by the reef and its biota. Nevertheless, the "scent" of food in the vicinity will cause it to protrude its head. G. mordax can be enticed into almost frenzied activity during day light hours with the presentation of good (i.e., chopped mackerel). Consequently, the eel is easily trapped either during the day or night, facilitating the collection of live specimens. At night some eels were observed swimming completely exposed over the rocky bottom. Predation on other species of fishes and crustaceans has also been observed during the late evening hours. Chave and Randall (1970) stated that only a few species of morays were known to leave their holes in search of food either during the day or night. If this statement was meant to apply to the behavior of the entire family, then I believe it to be an unsupported generaliza tion. Too few observations have been made of those many other species within this large family to say with any Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 55 certainty that morays seldom swim over the reef. Because both diurnal and nocturnal behavior in different species of morays has been noted, and since isolated observations of the activity of individuals within a species does not necessarily define the behavioral activity of that species, I decided to conduct a study that would continuously moni tor the activity of a small population of G. mordax over a period of weeks. Methods and materials The G. mordax used in this experiment were collected in the immediate vicinity of the Santa Catalina Marine Biological Laboratory. Eight eels ranging from 9^0 to 1061 mm TL were utilized in the experiment. They were cap tured in approximately 5 m of water using a fish trap baited with chopped mackerel. A Sears-Roebuck and Company wading pool two feet deep and eight feet in diameter was arranged near the water's edge and provided with running sea water. The flow into the 650-gallon "aquarium" insured a complete change of water every hour. This rate was sufficient to prevent heating of the unshaded pool water by more than 1°C above ambient sea w&ter surface temperature. Sections of tile sewer pipe and pieces of both 10 cm and 15 cm diameter polyvinylchloride (PVC) pipe were placed in the pool as shelters for the eels. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Swimming activity of the eels was monitored with electro-mechanical sensors similar in principle to those described by Spoor (1941) and Davis (1964). A length of 13 mm inside diameter (1/2 in.) electrical conduit was used to span the diameter of the aquarium. Machined brass plugs with axles 6.5 mm (1/4 in.) in diameter and 19 mm (3/4 in.) long were soldered into each end of the conduit (Fig. 6). Wooden supports constructed on opposite sides of the pool platform held the conduit in position across the top of the tank. A 3*5 mm-thick teflon piece, drilled with a 6.5 mm hole and screwed securely to each support, served as "bearings" for the brass axles. The combination of brass and teflon insured that the conduit would rotate freely since neither would corrode even when in close proximity to sea water. Lubrication was also unnecessary, as the teflon provided a low-friction surface. Locomotion detectors, similar to those described by Davis (1964), were rigidly affixed to either end of the conduit so as to hang in the water without touching the bottom of the aquarium (Fig. 7). The vertical wires of these 460 mm by 610 mm detectors, constructed from 3*5 mm gas welding rod, were 38 mm apart. Two horizontal bars were welded at their ends on either side of the frame and half way down it. This permitted the vertical wires lateral movement but restricted motion at 90° to the horizontal bars. This design permitted an eel to easily Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 6 One-half inch conduit showing end with machined brass plug and axle. 57 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CONDUIT h N ^ ) CM Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. cm Figure 7 Cutaway diagram of pool with activity-monitor ing device in place. (Switch and mount have been deleted to improve clarity of drawing). 59 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TEFLON BEARING 60 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. part the bars of the detectors when swimming through* but friction of the eel's body against the rods (and the restricted back and forth movement of those rods) caused the entire detector to swing either one direction or the other. This action caused the rotation of the conduit supporting the two locomotion detectors. To translate this action into an electrical signal a cam (Pig. 8) was machined to slip over the conduit. A set screw in the cam insured proper positioning on the pipe. A 15 amp, 125 volt AC roller-bearing micro-switch from Underwriters Laboratory, Inc., was adjustably mounted on the wooden pipe support so the roller of the micro-switch rode on top of the cam peak when the detectors were at rest (Pig. 9). In this position the circuit was open (Pig. 10). A slight movement of the detectors in either direction caused by a passing fish resulted in rotation of the cam with subse quent closing of the circuit by the switch. These electri cal impulses were recorded by an Esterline-Angus graphic ammeter, Model A601C. Because only a curvilinear single channel chart recorder was available, the swing of the pen was damped to half scale using an adjustable type 50K, 50W resistor. A six-volt Eveready lantern battery #509 provided the electrical power in the circuit. Results The results of the 4-5 days of recorded activity of Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 8, Cam design used on activity-monitoring apparatus. 62 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 63 CAM SET-SCREW 2 cm Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 9. Cam and switch in position. Switch mounted on adjustable plate to permit precision placement of roller-bearing lever. Sensitivity of moni toring mechanism can be adjusted in the same manner. 64 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 65 VERTICAL ADJUSTABLE SUPPORT MOUNT CAM 1WITCH1 ^TO RECORDER Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 10. Circuitry used in conjunction with Bsterline- Angus chart recorder to monitor moray eel activity. 66 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 67 w o o M Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 68 the morays is-presented in Figure 11. Days on which no activity was recorded were due to mechanical failure. The data presented was transcribed directly from the original Fsterline-Angus recordings. The eels were fed throughout the duration of the experiment. Spanish mackerel, pur chased commercially and chopped into pieces, were readily devoured by the eels. The amount of food given the ani mals was a maintenance ration and did not satiate the eels. The hour of feeding was random and daily, except for occasional interruptions when the animals were not fed for up to three days. No alteration in activity behavior was apparent. Table k presents the averaged percentage of activity for each hour of the day over the duration of the study. Percentages were calculated by summing the number of recorded spikes during each hour and dividing this by the total number of spikes for ^5 days. Only 13# of the morays' activity was conducted during daylight. Usually during the day they were found resting within the provided pipe shelters, sometimes as many as six in one piece of 15 cm diameter PVC pipe, 3.3 m long. Swimming, a circling of the perimeter of the pool, began between 1700 and 1800 hours and continued through the night until 0600 hours, accounting for 87# of the eels' activity. The observed nighttime swimming activity would begin feebly two hours before sunset between July 31* and Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 11. Recorded activity of Gvmnothorax mordax. Hours of darkness for each day indicated by heavy, dark, horizontal line. 69 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1 I I III. ii m ii miimb ii 8 12 lin w im B B U U lU B J s a iiaagggaaBiiiaiii i i m ikh i i m ■■mill i »■!» II 111 III ■ II ■■■ II 16 20 III ____ _11 «lllH ■ I I I ! I ■ zw 28 . UK III III II I II IBII 32 III IBII 36 ■■LIIIBIIIIJJLL ■BilBIIIIIIIII | | i|| IB a n am in 1 I L L II III BIIIIHKIIBIB ■ iii imui II uuii b 8 12 16 20 12 TIMS O f DAY Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 4. Averaged percentage of activity for each hour of the day over the ^5-day activity study period, based on the total number of activity spikes. •Total equals 102.7# due to rounding off figures. 71 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Hour ^Percentage of activity 1200 0.2 1300 0.2 1400 0.2 1500 0.9 1600 1.0 1700 3.0 1800 4. 0 1900 5.0 2000 8.0 2100 10.0 2200 11.0 2300 10.0 2400 9.0 0100 9.0 0200 8.0 0300 7.0 0400 7.0 0500 6.0 0600 0.9 0700 0.9 0800 0.8 0900 0.2 1000 0.3 1100 0.1 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. September 22, 1971 (an increase from observed activity levels of 156/hour during 1600-1700 hours to 3#/hour dur ing 1700-1800 hours). This activity level continued increasing to 5^/hour through sunset at 1900-2000 hours, jumped to 8^/hour with dark at the end of twilight (2000- 2100 hours), and increased to a maximum activity level of 1156/hour exhibited during 2200-2300 hours. From this time swimming decreased gradually to 696/hour at 0500-0600 hours. With the arrival of dawn at 0600-0700 hours, the activity level dropped abruptly to less than 196/hour, then continued in this range until the onset of the next cycle. During the hour of least activity (1100-1200 hours), the minimum, mean, and maximum number of spikes observed were 0,0 - 0,08 - 2, whereas during the period of greatest activity (2200-2300 hours), the minimum, mean, and maximum values were 0.0 - 10.2 - 15. Discussion The very strong nocturnal activity level of 87^ indicates that feeding probably most often occurs at night. However, feeding is not restricted to the dark hours. Though forays for food occur at night away from cover, I have observed morays to attack fish exhibiting erratic behavior during daylight hours. In each instance the fish attacked had escaped from a spear and in seeking a hiding place on the bottom, inadvertently swam into a Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 7^ hole concealing a moray. Hobson (1968) has made similar observations on G. castaneus in the Gulf of California* he (1968188) stated that this moray seems especially sensitive to “stimuli emanating from or suggesting injured and/or distressed prey*" Gvmnothorax mordax appears to be very sensitive to these same stimuli as well* The advantage of nocturnal activities to this moray eel can be hypCthesized. Hobson (1968) noted that the few fishes active nocturnally are all predators and feed on small motile invertebrates, particularly crustaceans. These prey become more available to the predator after dark when they too become active and are exposed. During daylight hours these same invertebrates are concealed and under cover. Bakus (1969) suggested that diurnal conceal ment by coral reef invertebrates may be the result of nat ural selection by fish predators. Gvmnothorax mordax is known to feed on the cleaner shrimp (Hippolysmata califor- nica). lobster (Panulirus interruptus). octopus (Octopus bimaculatus and 0. bimaculoides). and squid (Loligo opal- escens). as well as various near-shore fishes (personal observation). Each of the invertebrates named is more commonly found exposed and active at night, a period during which the moray has little competition for these food resources. Fishes consumed are most probably taken whenever the opportunity arises (as previously discussed). Opportunistic, diurnal feeding by other nocturnal pred Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 75 ators has been observed by Starck and Davis (1966) and Hobson (1968). Over the 45-day study period the nocturnal activity level averaged 83 recorded spikes per night. During two 6- day periods this activity level was considerably higher. The mean number of recorded spikes during the nighttime hours over these two periods was 148 and 118. Activity of some fishes is known to be coordinated with phases of the moon, e.g., grunion (Walker, 1952). A similar pattern was sought for in the recorded data for the California moray. It was discovered that the dates of the two periods previously mentioned appeared to correspond to lunar periodicity. The first 6-day period with increased noc turnal activity occurred during the last 3 days of the moon's last quarter and the first 3 days of the new moon. The second 6-day period of increased nocturnal activity occurred during the first 6 days of the new moon on the following month. During the one and one-half months of monitoring eel activity, peaks of swimming closely coin cided with the onset of the new moon, the darkest nights. In order that this behavior pattern be substantiated further activity-monitoring studies need to be conducted over a period of several months. It can be postulated that the advantage of this behavior is that the eel popula tion is most active and thus exposed to predation (Starck and Davis, 19661 Hobson, 1968). Observations of the prey Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 76 of moray eels need to be made and their activity periods recorded in order that this hypothesis be supported or refuted. Food and Feeding Introduction Only moderate amounts of information are available on the feeding habits and behavior of muraenids. Most of these data have been collected in conjunction with studies of fish populations in selected regions. Lack of research on this group of fishes may be due in part to the habitat occupied by morays and their fierce, threatening appearance That they commonly conceal themselves within caves of the reef and, as a group, seem to be primarily nocturnal, are behavioral traits that make them more difficult to study. The California moray, Gvmnothorax mordax is no exception. Methods and materials Specimens for this study were collected using baited traps set in the rocky subtidal in the vicinity of the Santa Catalina Marine Biological Laboratory. The captured individuals were sacrifiedd, weighed and measured, and an identifying tag was affixed. The stomach and intestines were examined for food items by dissecting them, then by washing the contents onto a fine screen sieve (0.1 mm). All organisms were identified as accurate ly as possible. From the beginning it was noticed that Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 77 much of the contents of the digestive tract was unidenti fiable digested material. Usually this material had a red or yellow color and a viscous consistency. Other eels collected in a similar manner for a tagging study were placed in individual buckets for weigh ing. Many times these eels would regurgitate food items in the stomach. Poods consumed naturally and those items consumed while an eel was in a trap were recorded sep arately. In order to analyze the food habits of G. mordax. each food itemewas listed along with the number and per centage of eels containing it. This method was chosen because it shows those items most frequently consumed. Pillay (1952) and Hiatt and Strasburg (i960) noted that this method is the most important for studies of food and feeding interrelationships. However, qualitative analysis can yield misleading results. The method of collection may provide the predators with opportunities to devour prey items that would otherwise be unavailable to them. Poisoning stations or live trapping can bias the data since large predators may consume the smaller fishes more quickly affected by the poison, or they may enter traps to consume other fishes contained within them. Care must be taken to exclude freshly devoured prey from consideration and utilize only those items naturally consumed to compile information on the feeding behavior of carnivores. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Quantitative analysis of the different food items ingested is hazardous also. One or a few large items devoured by a fish may not be indicative of its usual diet because it may be a feeding opportunist. Often it is clear from examination of the combined information on gut contents for a species that certain items are found in most of the fish, though their percentages of the total volume may be small. On the other hand, a single large food item in one fish will comprise the major percentage of the total volume in the gut of that fish. Though ingestion of this food type may be infrequent, in the final analysis it may appear to be of greater importance to the diet of that species than it actually is. With this in mind and because the methods used to collect gut contents from G. mordax were not expected to give accurate quan titative results, it was decided to use a qualitative analysis of feeding behavior. Results Eighty-eight G. mordax were examined for gut con tents after sacrificing the animal. Of these, 81^ had either empty digestive tracts or unidentifiable digested material in the gut. Of the 116 animals collected for a tagging study, 66% regurgitated nothing, or if regurgita tion occurred, the material occurred in small amounts and was unrecognizable. Tables 5 and 6 present the lnforma- Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 5 Stomach content analysis of Gymnothorax mordax* including food ingested while eels and prey were confined in a trap. 79 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. No. of food No. of morays Percentage of items of containing eels ingest- each type the item ing that item Percentage of items consumed in 3 major groups Pachvsrapsus crassipes Hippolysmata californica Panulirus interruptus 1 2 6 1 1 10 1 2 18 2 22 (crustaceans) Octopus sp. Loliffo opalescens 7 13 7 6 13 11 24 (molluscs) Embiotoca .iacksoni Brachyistius frenatus Cypselurus californicus Pimelometopon pulchrum Chromis punctipinnis Heterostichus rostratus Paralabrax clathratus unidentified fish fragments 2 4 1 1 7 1 41 4 2 3 1 1 6 1 27 4 4 5 2 2 11 2 48 7 79 (fishes) Total 56 (28% of all eels examined) Table 6. Pood of Gymnothorax mordax in the natural environment. 81 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. No. of food No. of morays items containing each type the item Percentage of eels ingest ing that item Percentage of items consumed in 3 major groups 26 Octopus sp. Loligo ooalescens Embiotoca iacksoni Brachvis'tius frenatus Cypselurus californfcus Chromis punctipinnis Paralab'rax clathratus unidentified fish fragments 1 3 10 29 1 3 7 21 6 18 1 3 1 3 1 3 6 18 1 3 4 13 35 (crustaceans) 39 (molluscs) 43 (fishes) Total 34 (17# of all eels examined) 8 3 tion gathered on food items consumed and the percentages of eels in which specific items were found. The data presented in Table 5 include those freshly consumed fishes regurgitated by trapped eels, food that was partially digested but eaten before entering the trap, and the items found in the gut of dissected morays. Of the 56 eels containing food items (18# of the total col lected), 22# had ingested crustaceans, 24# had eaten cephalopods, and 79# had consumed fishes. Seventy-two per cent of all the fishes consumed were eaten by the moray while both predator and prey were confined in the trap. Of these, 89# were small (12-25 cm standard length) kelp bass, Paralabrax clathratus. These serranids, very abundant over rocky subtidal regions supporting Macroc.vstls beds, are atracted to and captured by the baited fish traps set for moray eels. Their frequency as a prey item is probably due to the fact that they, more so than other fishes, are captured in relatively high numbers (20-40 per trap). Table 6 presents those food items consumed before the eel entered the trap. (Prey devoured while the eels were in the trap was obvious from its fresh condition, while naturally-eaten items were in various stages of digestion.) Of the 34 morays (17# of the total) that were found to have identifiable material in the gut, 35# of these had eaten crustaceans, 39# had consumed cephalopods, Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 84 and 43$ had ingested fishes. Morays that had eaten small crustaceans ranged from 575 mm to 905 mm TL, the average length being 663 mm TL. Cephalopods were consumed by eels ranging in size from 783 mm to 1090 mm TL, the mean size being 918 mm TL. The average size of those morays that had consumed fishes was 970 mm TL with the range between 753 ram and 1245 mm TL. Discussion The following authors have investigated the feeding behavior of various moray eelst Suyehiro, 19421 Al- Hussaini, 1947; MacGinitie and MacGinitie, 1949; Morris, 1959* Takai and Tsutsumi, 1959; Winn and Bardaeh, 1959; Bardaeh et al., .1959; Hiatt and Strasburg, I960; Bardaeh and Loewenthal, 196I1 Davis and Bardaeh, 1965; Starck and Davis, 19661 Randall, 19671 Hobson, 19681 Randall, 1969; and Chave and Randall, 1970. Each of these has found that the morays investigated, whether nocturnally or diurnally active, consumed primarily benthic crustaceans, ^•e., various crabs and shrimps, while fishes made up a small percentage of the diet. Generally, it has been found that many eels in a collection will have empty digestive tracts (Hiatt and Strasburg, i960). The percent age of eels without identifiable material in the stomach and gut usually ranges between 60$ and 80#, though some authors have reported all eels in small collections of a Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. single specieB to have empty digestive tracts. Personal observation indicates that this may be due to the behavior of morays when subjected to stress. Commonly, these eels will regurgitate their stomach contents when subjected to harsh conditions, such as being (1) exposed to poison. (2) speared* (3) lifted from the water in a trap. (*0 placed in a dry bucket, or (5) handled roughly. Though this regurgitation reflex was used advantageously in a study of feeding behavior of G. mordax. it is possible that other workers have observed eels that had recently regurgitated a meal and were consequently reported as having empty stomachs. Another reason proposed by Hiatt and Strasburg (I960) to explain the high percentage of empty stomachs Wasthat the eels were feeding at night and had digested the food items before their collection the following day. Each one of the 116 specimens of G. mordax col lected for a tagging study was placed in a bucket without sea water. This treatment was usually sufficient to pro duce the regurgitation reflex. Any identifiable items were noted and recorded along with the length and weight of the eel. A total of of the eels examined in this manner had identifiable stomach contents. This percentage com pares favorably with those found by other workers. How ever. this method has serious shortcomings. Some eels regurgitate while being lifted from the water while inside Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 86 the trap or later while awaiting removal to a bucket* This occasionally makes it difficult to determine the food item’s source. Additionally* there may possibly be some recognizable food fragments in the gut of the animal* and without sacrificing it the presence and nature of these cannot be determined. Nevertheless, regurgitation is con venient to use and does afford some insight as to those groups of animals from which food items are selected. It was mentioned previously that caution must be taken when conducting food habit observations of carnivores for the contents of the digestive tract may be a conse quence of the collecting method. This effect is observed with both poisoning and trapping techniques. To minimize this, trapping of eels was carried out in the morning and evening when naturally consumed food items would still be in the stomach. The trap was checked three hours after setting and examination of food habits then conducted either by sacrifice or regurgitation. Those fishes con sumed while the eel was in the trap were immediately recognizable due to their fresh condition. Also because large numbers of the kelp bass Paralabrax clathratua were attracted to and caught in the trap, this was the species usually consumed by the eels. A comparison of Tables 5 and 6 shows this to be true and serves as graphic evidence that interpretation of feeding behavior can be signifi cantly altered if these unnaturally ingested items are not Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 8? discounted. It can be seen in Table 6 that 35# of the morays ingested crustaceans. Of the 20*f eels examined, 29# had eaten the cleaner shrimp Hippolvsmata californioa. an organism that is often found in association with the eel and may occasionally be seen walking over the moray*s head apparently removing parasites from the host. These shrimps and a single shore crab found in the gut were eaten by small morays averaging 663 mm TL. The antennae and their bases, head and a portion of the carapace of a spiny lobster (Panulirus interruptus). estimated to have been about 25 cm TL without antennae, was found in the stomach of a large moray 1152 mm TL. MacGinitie and MacGinitie (19^9) observed predation by G. mordax on Octopus bimaculatus. Their report de scribed seeking by the predator, the avoidance and escape response of the octopus, and the eventual consumption of either part or all of the octopus by the moray. In this description they reported a behavioral response of this eel which throws a knot in its tail and passes this anteriorly over the body. The effect is to remove an octopus cling ing to the moray*s head. I have observed similar responses by these eels when snared around the neck with a "noose," a device used to capture eels alive. This behavior is a successful escape mechanism from the noose as well as the octopus. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Of those other authors cited previously. Starck and Davis (1966) reported another raoray, a Caribbean . species G. moringa. to have fed on octopus. Morris (1959) found octopus tentacles and beaks in the stomachs of some Hawaiian muraenids, while Randall (1969) stated that octo* pus is a favorite food of raoray eels. Table 6 shows that of the eels examined. 21# contained octopus and another 18# contained squid. The octopus is likely a year-around prey, whereas the squid is seasonal and probably consumed during those periods of reproduction when this species is abundant inside Big Fisherman Cove. As noted by other workers (Hiatt and Strasburg, 196G1 Randall, 19671 Hobson, 1968), fishes will likely be eaten whenever the opportunity presents itself. That they are preferred to other items in the diet seems appar ent from Table 5» However, raorays probably rarely pursue, attack, and devour a healthy fish. Perhaps the relatively high incidence of blacksmith, Chromis punctipinnis. among the fishes consumed is due to the fact that this species seeks refuge among the crevices and caves of rocky reefs during the night, that period when the morays are most actively searching the reef. Other recognizable fishes comprise 12# of the total consumed. Two of these species, Embiotoca iacksoni and Paralabrax elathratus. occur near shore close to the bottom both day and night, and were possibly unwary or sick individuals. The flying fish, Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Cypselurue californicus. and kelp perch Brachvistius frenatus. are usually off the bottom some distance but may also have been sickly and devoured when exhibiting unnatu ral behavior in the vicinity of an eel. Pitch and Laven- bert (1971) reported that a large moray examined by them had eaten two flying fish. More than one-third of those food items eaten by G. mordax were fishes. Starek and Davis (1966) reported that the Caribbean species, Bnchely- core nigricanus. Gvmnothorax funebris. and G. moringa are principally fish eaters, Randall (1967) concurred with this conclusion for both of these species of Gymnothorax and added G. vicinua as another piscivore. The studies of Hawaiian morays by Morris (1959) and of Eniwetok eels by Hiatt and Strasburg (i960) showed many to be primarily crustacean feeders, with the exception of G. .lavanlcus. G. flavimarginatus. and G. undulatus. However, these workers* observations are incomplete, and not all eels inhabiting the area were investigated. Bakus (1969) compared the feeding specialization of ecologically equivalent tropical and temperate wrasses. To do this he suggested the use of an equation which would yield a value, the food index. This equation appears as P * A(xj + x2 + . . . xn) + P(yj + y2 + . . . yn) where A is animal food, P is plant food, and x and y are the per centage of fishes containing a particular food category (Bakus, 1969*33*0• The value of A or P is 1 when the fish Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 90 has consumed items from only one category. A * 2 and P * 1 when the animal is omnivorous but eats more animal food than plant food. A ■ 1 and P * = 2 when more plant food than animal food is consumed. P « food index, a unitless value used as an indication of feeding specializa tion and inversely proportional to it. When there is a high degree of feeding specialization the value of F ap proaches 1, a value which increases as feeding becomes less specialized. Three food categories (crustaceans, molluscs, and fishes) were established for the morays compared here. The maximum value of F is 3. A food index of 1.17 was calcu lated for G. mordax using the percentage of food items in each of three categories. This was compared with ecologic ally equivalent morays collected in the Marshall Islands by Hiatt and Strasburg (i960). The food indices cal culated for four species of Gymnothorax are as follows: G. buroensis. F » 1.75* G. flavimarginatus. F » 1.25* G. .iavanicus. F * 1.00: G. rictus. F = 1.25. It appears that the feeding specialization of the temperate moray 3* mordax is similar to that of these tropical species in the same genus. However, these F values are very rough comparisons. More accurate determination of feeding specialization requires the use of species level food categories. Insufficient data on the food of tropical morays prevented this type of feeding specialization Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 9 1 analysis. Also variation in the mean size range of dif ferent raoray species is probably reflected in the respec tive diets, the relative size of the gape. jaws. etc.. determining, in part, the food items consumed. Since G. buroensis is smaller than G, mordax. differences in the respective diets may be responsible for the moderate dis crepancies in their values of P. General ecological theory supports the belief that where species diversity is higher (or where interspecific competition is more intense), niches are smaller. Terri tories would be expected to be smaller as well and feeding habits more specialized in the tropics (Klopfer. 1962t Rosenblatt, et al., 1972* and others). Theoretically then, one might expect tropical muraenids to exhibit greater feeding specialization (lower P values) than temperate rep resentatives. That this is not the case may be due to the fact that these morays can be considered to be top carni vores and probably have little competition for certain food resources from other fishes. Prom the data tabulated in Table 5 it is apparent that Gvmnothorax mordax occupies the fourth trophic level (Hiatt and Strasburg,.1960). However, it may be more real istic to consider the concept of a trophic spectrum rather than trophic levels (see Darnell, 1968). Sixty-nine per cent of this eel's diet is composed of secondary consumers, or occupants of the third trophic level. The fishes and Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. cephalopoda are primarily carnivores, eating many herbi vores (primary consumers)9 and being preyed upon by another carnivore, the moray. This most likely makes the California moray eel one of the top predators in the near shore marine environment. Certainly as an adult, it is one of the larger fishes found in the shallow subtidal regions. It probably encounters little competition as an adult ex cept from members of its species. Also, adult G. mordax are probably not prone to predation by other fishes. Per haps their larvae or juveniles may be food for some species, though there is no record of this. Data presented earlier indicate that there is a general change in the size of prey with increasing size of the predators. It was shown, by averaging the sizes of the morays containing specific prey groups, that smaller eels had consumed small-size crustaceans* cephalopods were eaten by larger eels* and fishes were ingested by still larger morays. Such a change should be expected as a greater volume of food must be necessary to sustain in creased body size. Energy would be conserved by devouring one or a few large items, rather than seeking and ingesting many small prey. McCleneghan (1968) found that Southern California wrasses (family Labridae) also demonstrate the selection of larger food items with increasing body size. These observations concur with those of Nikolsky (1963) who also stated that change in diet composition with age Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 93 results in increasing those foods available to a popula tion. Length-Weight Relationship Introduction An important aspect of growth is the relationship between length and weight. For a number of fish species the weight increases with the cube of the length, while others add weight at a rate greater or less than the cube (O'Connell, 1953* Rounsefell and Everhart, 1953* Carlisle, Schott and Abramson, I96O1 Young, 19631 Phillips, 196*0. O'Connell (1953 suggested that variations from the cube relationship were due to minor changes in the basic fusi form shape with growth. Eels which exhibit pronounced attenuation of the fusiform condition might be expected to vary from this relationship. In order to calculate growth a time factor must be utilized. This is usually expressed as age. Attempts to determine age in G. mordax were not altogether successful, and the information gathered was inadequate to develop firmly a reliable annual length- weight increase or growth function. Nevertheless, compil ation of length-weight data would be worthwhile for later investigations and instructive as to possible sexual dimorphism. Also length-weight curves might give some information as to an eel's size at maturity. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 9 4 Methods and materials Morays used for the calculation of length-weight curves were those from Santa Catalina Island and Dana Point* California* Measurements of length were made to the nearest millimeter and weight to the nearest gram. Lengths and weights were plotted separately for the 71 males and 50 females examined (Pig. 5). This graph indi cates that G. mordax females probably do not attain the sise reached by the males* Moreover* at a given length it appears as if the non-reproductive females do not weigh as much as the males* In order to determine whether dif ferences between the length-weight relationships of male and female G. mordax were significant, a t test was con ducted using the slope or •'line of best fit" for each group. A regression analysis was carried out after the data had been transformed to give a linear function. This was accomplished by using the length in millimeters vs. the log^Q the weight* Those specimens below 400 mm TL were not considered in the calculations as they did not conform to a linear function. Results Figures 12 and 13 illustrate the scatter diagram for data on the males and females respectively. The re gression line for each was calculated using the method of least squares (Woolf, 1968). Since logjo values were used Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 12. Relationship between total length ( hub) and weight (gins) for Gymnothorax mordax males. 95 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. WEIGHT (GMS) 96 5.000 100 50 10 600 800 1000 1200 400 200 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 13• Relationship between total length (nun) and weight (gms) for Gvmnothorax mordax females. 97 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 98 5.000 1000 100 50 10 600 800 1000 1200 200 TOTAL LENGTH Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. for the weight, the linear equation becomes log1QY * a + bX where g. is the Y-intercept, and b is the slope. For the males, a * 8 1,9599 and b * 1.374? * 10"^» whereas for nential function of the base 10, Computing these one finds the Y-intercepts to be 91 gms and 28 gms for males and females respectively. For males the mean length (x) was 937 mm, with a mean weight (y) of 1?67 gms. For females x was calculated to be 758 mm and y equaled 903 gms. A pooled variance was calculated using the formula of Woolf (1968)* where d * Y - Y, or in other words, the deviation between the observed point (Y) and the estimated value of Y (Y). carried out. It was determined that the value of t for 114 degrees of freedom was 3«31» a figure significant At the 99% level. In other words, there exists a 1% proba bility that such a difference between the slopes of the two lines is due to chance. Discussion From the data presented here it is apparent that these morays exhibit some sexual dimorphism, at least above lengths of 500 ram TL. However, it is doubtful females, a * 1.4484 and b * 1.9886 • 10”^, a is an expo- SyX (pooled)2 » (n - 2) + (n - i) 1 2 The pooled variance was necessary to permit a t test to be Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 100 whether individual live morays eould be accurately sexed below a length of 1000 mm TL. Even here considerable scatter is encountered on the graphs( due to individual variation. Carlisle et al., (I960) observed that for the bar red surf perch, Amphistichus argenteus. two regression lines are required to define the length-weight relation ship. One regression line was fitted to the data for those sizes of fishes up to 180 mm standard length (SL), and another line was calculated for lengths above 180 mm SL. Using the slopes of these two lines, a t test indi cated that they were significantly different at p » .01 probability. The authors suggested that the change in slope was probably a reflection of morphometric changes associated with the onset of maturity. Figure 12 shows the regression line for male G. mordax. Those points below 400 mm TL were deleted from the calculations for reasons previously discussed (see p.93). Two additional points in the 500 mm TL range were included in the calculations. However, these appear not to lie within the linear function described by the majority of points. Moreover, a line drawn through the two points of 329 mm and 348 mm TL passes almost directly through those points at 520 mm and 542 mm TL. Recalculating the regres sion line for the remaining points above 600 mm and plot ting this, one finds that it crosses the lower line at Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 101 600 mm TL.and 1500 gma of weight (Fig* 1*0. It seems pos sible that 6* mordax also exhibits a change in the length- weight relationship at maturity* although additional data are necessary below 600 mm TL to definitely establish this. A t test was conducted on the difference between the slope of the new line for male G. mordax (less the 300 mm and 500 mm TL points) and the previously computed line for females. These* too* were significantly different at a level of p * .01 probability. Age Introduction Various methods have long been used to determine the age of fish (Perlmutter* 195*0* Examinations of scales* bones* and/or otoliths for annual growth rings are the most common of these. Otoliths were utilised here because they were more convenient to collect than bones and because the moray eel lacks scales. Methods and materials Otoliths were collected from each Gvmnothorax mor dax sacrificed in order that age might be determined. To remove the sagittae (otoliths)* the eel was placed ventral side up in a holding trough. An incision was made along the ventral midline between the mandibles* This exposed the roof of the mouth where another anterior-posterior cut exposed the ventral surface of the brain case. Bone snips Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 14>. Two rectilinear regression lines showing the relationship between total length (nm) and weight (gms) in male Gvrnnothorax mordax. Upper line fitted by calculation, lower line fitted by sight. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. WEIGHT (GMS) 10 I I I I 1 ---1 ---* ---1 ---' ---1 ---1 ---1 ---L 200 400 600 800 1000 1200 TOTAL LENGTH (MK) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 104 were carefully used to cut away the heavily ossified otic bulla without damaging the otoliths. Removal of some of this bone exposed the sagittae which were easily extracted with a forceps. The otoliths were cleaned and dried and placed in a dry vial along with an identifying label. Examination of the otolith pairs was carried out under a dissecting scope using a Stender dish containing a disc of black glass to provide a suitable viewing back ground (Schott. 1965)* The Stender dish was filled with toluene in which the sagittae were submerged. This fluid acts to "clear" the otolith making the transparent and opaque rings more distinct. Counts were made following Jensen (1965) and Smith (1968). Nevertheless, counts were difficult as those otoliths of 6. mordax examined were small (1.7 - 5*6 mm in greatest length) and opaque. Results Fifty pairs of moray otoliths were examined and from two to twenty-two zones were counted. Jack Schott (personal communication) believes these zones to be annual rings because of their spacing. The first ring outside the nucleus is the broadest with the width of each successive zone diminishing as one proceeds toward the edge of the otolith (area of growth). That morays can attain consider able age. at least in captivity, has been noted by Fitch and Lavenberg (1971). They reported that a specimen of Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 105 £. mordax lived for 26 years in an aquarium* It was found that small morays (300*400 mm TL) had 2 or 3 tones on the otoliths* Eels of about 550 mm TL had 4 zones* whereas those of 600-700 mm TL and 700-800 mm TL had 5 and 6 zones respectively. Seven and eight zones were counted in those eels between 800 and 900 ram TL, Those morays in the low 900 mm TL range had 9 zones with 10 zones on the otoliths, while some individuals less than 1000 mm TL had 10 zones on the otoliths. One eel of 1100 mm TL had 13 zones on its otoliths, and another of 1100 mm TL had 22 zones. Discussion This discrepancy between length and age is probably due to the fact that as the eel approaches the upper limit of length for its species, its growth slows. As a result, a relatively young eel may be almost as large as another older one. Sometimes it appears that this condition may even be reversed* older eels being shorter than younger individuals• Reproduction Introduction The breeding behavior and time and site of spawning remain to be discovered for the California moray eel. This is not unusual though, as most morays have not had their life history described. The first complete study of Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 106 this type was conducted by Eldred (1969b), who described spawning times and locations, eggs and their development, and larvae and elvers of Gymnothorax nigromarginatus in the Caribbean. Though the larvae of some Indo-Pacific muraenids that also occur in the tropical east-Pacific have been described, none of the 2? known species of east- Pacific morays has completely known life histories. Until now, not even a single larva of any east-Pacific endemic moray had been described. The attempt to elucidate the breeding behavior and early life history of G. mordax was only moderately successful. Though its larva is described herein, facts concerning its breeding behavior could not be determined from various observational studies. Never theless, certain hypotheses have been formulated. Methods and materials To determine the breeding season of the California moray eel, collections of adults were made in the vicinity of the SCMBL each month of 1970. Trapping eels in baited fish traps accounted for about two-thirds of the animals collected. In order that this method not bias the sample by excluding animals that were not feeding, supplementary collections were made using scuba and a speargun. The remainder were captured by hand by members of the Califor nia Department of Fish and Game when sea water contained behind a coffer dam was drained away during the construc Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 107 tion of the Dana Point Marina at Dana Point, California. The date, time, area of depth of capture, along with the length, weight, sex, and weight of the gonads were recorded for each eeli 125 animals were treated in this manner. Results Gross examination did not reveal any apparent changes in the state of the gonads of either the males or females throughout the 12-month study. Typically the testes appeared small, white, and ribbon-like, but were slightly thickened along their length. Usually the right testis was noticeably longer than the left. The yellow- orange ovaries were immediately distinguishable from testes and exhibited a granular appearance. The eggs contained within the gonad were small, less than 0.5 mm and did not change in appearance from month to month. Females also exhibited a right gonad longer than the left. Examination of a collection of large G. mordax made at San Diego in June, 1971* showed the gonads to be in the same condition as those described from Santa Catalina Island. Discussion Though no change in gonads of either males or females was apparent by visual inspection, there was a change taking place in the ratio:of gonad weight to body weight. Plotting the monthly ranges of these ratios for Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 108 both sexes separately showed that there was an increase in this ratio each month until a peak was reached in July, whereupon the ratio then gradually decreased during fall and winter* With the exception of one specimen, specimens of if* nordax held in the collections of various museums and institutions showed a similar lack of gonadal development. In the collection of the Los Angeles County Museum (LACM), there is a female G, mordax (W55-112) of 910 mm TL col lected with baited hook and line off the jetty of the entrance to Magdalena Bay, Baja California, on April 9* 1955* This moray had large, well-developed ovaries con taining eggs of 1.5 mm in diameter. Though these eggs were larger than any previously seen, it is probable that spawning was-not imminent, as other workers report recently spawned muraenid eggs to be much larger. Schmidt (1913) found that the eggs of Muraena helena are 4.0 - 4,5.mm in diameter. An unidentified species of Muraena was reported by Ganapati and Raju (I960) to have eggs with a diameter of 3*2 - 3*6 mm, and Eldred (1969b) found the eggs of G. nigromarginatus to be 3.3 - 4.0 mm in diameter. Never theless, it is difficult to predict exactly the date of spawning since the sise of spawned G. mordax eggs remains unknown. Another complicating factor is that in the final stages of ripening, the eggs of many teleosts become much larger and buoyant by acquiring low density, watery fluids Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 109 from the follicle cells (Marshall, 1965)• These factors cannot toe ignored* However* if one considers the differ ences in diameter between those ova in the ovary of the LACM specimen of G. mordax and those spawned eggs described for other species* it seems reasonable to assume that the spawning of this moray was still some months away. Surface sea water temperatures recorded concurrently with the Santa Catalina Island collections show a general trend of increase from 14.0° C in January, to a peak in late July of 20.2° C, and another in mid-August of 21.6° C. Surface temperature climbed sharply from less than 14,0° C in late April to above ,18.0° C in the first week in June. The temperature remained above this level until October 22, but only from July 1 to the first of September was it above 19.0° C. Moreover* similar recordings of sea water temperature made at a depth of 20 m show that only on two brief occasions, from August 15*20, and again on August 30 to September 8, did the temperature rise above 18.0° C. Throughout July the temperature at 20 m was below 16.6° C. It is possible that the temperature of the sea water in the northern limits of the range of this moray does not remain for a sufficient period of time at the level required by this species for completion of egg and sperm development. Hutchins (1947) was the first to elaborate on observations made by others, which indicated that organisms Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 110 have different temperature requirements and tolerances at different periods in their life histories. He reported that not only was there a maximum and minimum temperature for survival, but a maximum and minimum temperature for repopulation as well. That certain hydrological criteria, especially temperature, are necessary for spawning is now a fact clearly established for most marine fishes (Marshall, 1965)» Moreover, this temperature range within which spawning occurs is usually rather restricted. Marshall (1965) also noted that summer spawners are usually fishes of tropical and subtropical distribution. Consid ering that muraenids are primarily a tropical group with some representatives in temperate regions, one should not be surprised to find that these family members in the higher latitudes retain the spawning behavior and require ments of their tropical relatives, though the adults are becoming adapted to different environments. As a conse quence, the geographical distribution of adults may extend beyond that area having suitable conditions in which spawning may occur. Castle (1968) reported a similar observation pertaining to the ophichthid and muraenid fauna in New Zealand waters. Even so, he believed that the distribution of a species is associated with the availabil ity of suitable regions and conditions in which spawning and larval development may occur. He also suggested that all eels, even temperate species, require water of about Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Ill 18.0° C for spawning to take place* though the adults nay live in much cooler waters.. This does not necessarily imply that long-range migration of adult moray eels is taking place. Rather, it is probably those eels in areas of their range offering suitable conditions that represent the breeding population. There are no reports that moray eels migrate for the purpose of spawning, though localised movements of individuals were apparent from the tagging study previously discussed. Eels were always in evidence in the vicinity of SCMBL, and large adults were seen and captured throughout the year. These observations indicate that G, mordax does not spawn in the northern parts of its geographical range. The collection of a female with maturing ova cells at Magdalena Bay, Baja California, suggests that migration out of the known range to an unknown spawning site is not occurring either. It is probable that this species is breeding and spawning within its known range, but only in those areas offering suitable hydrological conditions. These areas are most likely along the Pacific coast of the Baja Peninsula south of Punta Eugenia. From the collection data for the larva described herein as being that of G. mordax and data for many other leptocephali examined by me, it appears that spawning by this species occurs in the habitat usually occupied by the eelst the rocky, subtidal reefs. Many muraenid larvae Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 112 have been collected using a night light and a dip net from boats anchored near the shore. It is likely that develop ment of the leptocephalus occurs here as well* for no larvae of Go mordax have been collected in the thousands of trawl stations occupied over the last 20 years by the California Cooperative Fisheries Investigations off the Pacific coast of Baja California. This implies that the eggs and larvae of this moray are generally found in an area not frequently sampled. The near-shore waters of the east Pacific Ocean along southern Baja California is such an area. Due to its remoteness and inaccessibility, little sampling has been conducted along this coast. It is believed that in this region G. mordax breeds and spawns. The eggs probably hatch in late summer or early fall, and the larvae develop in shallow water while being carried by the various inshore currents, .i.e., long-shore drift, localized eddies, and tides. It is hypothesized that the north-flowing California Countercurrent (see Chapter IV), which develops in the fall off the coast of Baja California, carries some of these larvae into California where they eventually undergo metamorphosis, the new juveniles settling down to a benthic existence. In this manner, repopulation is accomplished in those areas of the geographical range where spawning does not occur. Current eddies within the countercurrent sys tem would account for the populations of California morays Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 113 on the offshore islands of California and Baja California, The duration of the planktonic leptocephalus stage would allow these larvae to occasionally cross the deep ocean waters between the mainland and the islands. Apparently this is an infrequent occurrence, for none of these larvae have been collected in the many trawl stations conducted off the coast of southern California, especially around the Channel Islands and off the west coast of Baja Cali fornia. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER IV SEA WATER CIRCULATION OPP THE COAST OP SOUTHERN CALIPORNIA AND BAJA CALIFORNIA Since 1949 personnel of the California Cooperative Oceanic Fisheries Investigations (CalCOFI) have made oceanographic surveys of water properties along the west coast of North America from Washington to Cabo San Lucas* Baja California. This extensive study provides an excel lent source of information on the general Ccean current patterns# The southeastern-flowing California Current, a con tinuation of the Aleutian Current, is the predominant sur face feature along the North American coast from ^8° to 23° N latitude# The western boundary of this current is approximately 700 kilometers off the coast at 32° N latitude (Sverdrup, Johnson, and Fleming, 19^2). The seasonal variability of this surface circulation is well documented (Reid, Roden, and wyilie, 195§t Emery, i960t Wooster and Reid, 1963* Wyilie, 19661 Jones, 1971)* In the spring and summer the current flows southeast between the East Pacific High Pressure Cell and the west coast of North America# This high pressure cell generates con- llfc Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 115 sistent northwest winds during this period which drive the California Current eastward toward the coast. In the fall and winter the high pressure cell becomes weaker* and the winds are less effective. Two new small high pressure cells develop, one characteristically over Nevada and the other off Baja California. The coastal winds during these months tend to blow from the southeast, at times at very high velocities (the Santa Ana winds) (Stevenson. I960* Jones. 1971). This shift in wind direc tion causes the southerly current to move offshore and the inshore surface waters to be accelerated towards the north. The combined actions of the westerly movement of the axis of the California Current and southeasterly winds cause an inshore surface countercurrent to develop (Sverdrup and Fleming* 19^1t Reid et al., 1958* Jones, 1971)* During the winter this countercurrent is present and contiguous along the North American coast from near the southern tip of Baja California to ^5° N latitude, near the mouth of the Columbia River, Oregon. South of Point Conception this countercurrent is called the California Countercurrent, while north of Point Conception it is known as the Davidson Current (Reid et al., 1958? Wooster and Reid, 1963). The water of the countercurrent is distinguished from that of the California Current by its higher temperature and salinity (State of California Marine Resources Commission, 1953)* The countercurrent remains as Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 116 an established feature of near-shore circulation until the northwesterly winds resume in the spring (Jones* 1971)* Another major oceanographic feature which is permanently established off California is the Southern Cal ifornia cyclonic eddy* This gyre occurs inside the sub merged peninsula* extending southeast from Point Conception towards Santa Rosa Island* San Nicholas Island* and Cortes Bank. The ocean water to the east of this is protected from the Northwest winds by the landmass of the Transverse Ranges and partially separated from the strong southeast- flowing offshore currents (Reid et al., 1958). This eddy remains even when the California Current is near-shore during the duramer months (Wyilie, 1966). Upwelling is another phenomenon that occurs along the west coast of California and Baja California. The development of upwelling and of its antithesis, the Cali fornia Countercurrent, depend upon the seasonal onshore and offshore migration of the southeasterly-flowing Cali fornia Current. The equatorward winds, which are roughly parallel to the coastt are strongest off Baja and Southern California in the spring and off Northern California in the summer. Consequently the location of most intense upwelling changes accordingly (Reid et al., 1958). Unlike California Current or Countercurrent water, upwelled water is characteristically of high salinity, low temperature, and low oxygen content, since the upwelled water originates Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. from th« depths (State of California Marine Research Committee, 1953)* A deep countercurrent, below 200 meters, persists along the coast even during the spring and summer months, the periods of upwelling. However, in the fall upwelling activity ceases, and the countercurrent redevel ops and is present at all depths on the coastal side of the California Current throughout late fall and winter (Sver drup et al., 19**2). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER V DESCRIPTIONS OF SOME MURABNID LEPTOCEPHALI PROM THE EASTERN PACIFIC Introduction Reliable identification of muraenid leptocephali have been made by Lea. 1913? D*Ancona, 1928a-c, 1932? Pantulu and Jones. 195^1 Ganapati and Raju, 1961? Castle. 1965? Della Croce and Castle. 1966? Blache, 1967a-f, 1971? Eldred, 1968a-b, 1969a-b, 19?0a-c). Castle (1965?p.59) characterised muraenid larvae as follows * Leptocephali of moderate size (few recorded examples being longer than 100 mm with most full- grown specimens at about 60 mm)? with a relatively shallow body, a short, blunt snout (except in young examples of less than 2$ mm) and a rounded caudal fin supported by few rays and two indistinct hypuralst the vent is never subterminal and even in early develop ment is usually placed in the middle of the body or a little behind this? the teeth are in moderate number (usually about 10 on each side of the jaws, in three groups)t the pectoral fin is seldom more than a minute fleshy flap (even in very small specimens), but is more usually absent? myomeres for the family from about 100 to about 220 with the range in any partic ular species usually about 10? pigmentation generally inconspicuous with the chromatophores relatively small, often distributed on the head, along the intestine, on the bases of the fin-rays or on the spinal cord, but so far not known to occur on the lateral body surface. However, identification of leptocephali to the species level remains a task of considerable difficulty. Castle 118 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 119 (1963) noted that those characters associated with a specific form of leptocephalus, e.g.* distribution of melanophores* vertical intestinal blood vessels, and denti tion and shape of the caudal fin, always fail to survive as structures during metamorphosis from the larva to the juve nile eel. Fortunately the number of myomeres in a larva continues unchanged through metamorphosis to the juvenile and adult eel. Jtyomere and vertebral numbers correspond, and though the myomeres are counted in leptocephali (or spinal ganglia may be substituted, as utilised by Castle, 1963), vertebral counts are more commonly used for adult eels. Because myomere and vertebral comparisons are major considerations in the identification of leptocephali to species, the determination of vertebral numbers in the various species was undertaken. Characteristics of Adults and Larvae of Eastern Pacific Muraenidae Vertebral counts can be made from prepared skele tons, but a more efficient method is radiography. Approx imately 120 X-rays were made of 21 muraenid species occur ring in the eastern Pacific. Data from these plates appear in Table 7. Myomere numbers are also included in this table for those species whose larvae are described elsewhere in the literature, as well as for those described here, Randall and McCosker (in press) examined a number of specimens of Gyranothorax nanamensis and found that the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 7, Vertebral counts of adult eels and myomere counts of described leptocephali for some species of eastern Pacific Muraenidae. Upper and lower limits of vertebral or myomere counts appear* along with the mean number* expressed to the first decimal place. ^Denotes eastern Pacific endemic species. **From Castle, 1968. ♦♦♦Vertebral cotints for Gymnothorax panamensis have been determined by Randall and McCosker (in press) and appear in Table 8. 120 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. Species Echidna nebulosa ♦Echidna nocturna Echidna zebra ♦Enchelvcore octavianuB Enchelvnassa*" canina Gvmnothorax buroensis ♦Gvrnnothorax castaneus ♦Gymnothorax dovii Gvrnnothorax flavimarglnatus ♦Gymnothorax mordax Gvrnnothorax panamensis Gvrnnothorax undulatus ♦Gyronothorax weineri Gymnothorax sp. Gymnothorax sp. *teaena argue ♦Muraena clepsydra ♦Muraena lentlginosa ♦Priodonophis angusticeps ♦Priodonophis eouatorialis No. of No. and mean No. of No, and mean Larvae No. of Larval Adults No. of Adult Examined ftyomeres Examined Vertebrae _ 124** 10 120-123.7-128 . - 7 118-120.4-122 - 135** 1 137 - 5 142-143.4-144 - 1^3-145** 1 143 - _ 5 110-113.0-119 - . 7 138-141.7-145 18 142-146.4-151 5 141-145.6-151 . _ 3 124-124.3-125 - - 4 134-135.5-138 1 145 17 142-148.3-152 _ . #** 1 133 12 127-130.2-133 - 125-131** - 125-131** 3 141-141,6-143 10 134-137.7-142 10 167-173.8-176 - - 1 117 - - _ 1 124 _ - 7 124-127.7-131 _ 10 114-116.7-118 . _ 1 138 - - 5 141-144.2-147 Table 8, Vertebral counts of specimens of Gymnothorax panamensis (from Randall and McCosker). 122 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 123 Locality Number of Specimens Vertebral counts and mean values Isla San Felix (off Chile) 4 141-143.2-150 Easter Island 10 140-141.8-144 Galapagos Islands 7 134-136.3-139 Isla Gorgona, Colombia 3 126-127.4-128 Panama (Pacific) 1 129.0 Clipperton Island 1 127.0 Isla Tres Marias 4 128-129.8-131 Cabo San Lucas 3 124-126.3-128 Gulf of California 5 123-125.0-126 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. m vertebral number varied with latitude (Table 8). It should be noted here that Castle (1963) observed the number of vertebrae in adult eels is usually one less than the number of myomeres in the larvae1 I have taken this into account when referring a leptocephalus to the adult species. Five species of Muraenidae belonging to the genera AnarchiaB and Uroptervgius occurring in the eastern Pacific have not been included on Talbe 7. Castle (1965. 1966), Blache (1967a). and Eldred (1968a-b) have described these genera as having the dorsal and anal fins much reduced and restricted to the caudal region. No larvae with this morphology are to be described here, and the adult verte bral counts for eastern Pacific species in these genera are not included on Table 7» Unlike the Anarchias-Uroptervgius group. Gymnothorax and related genera have a long dorsal fin which originates a few myomeres behind, to many myomeres in advance of. the level of the vent (Castle, 1965). This is true even of small specimens. Solomon Raju (personal communication) and Castle (1965) further described Gymnothorax larvae as having the dorsal fin origin over the branchial region. Rabula. on the other hand, is described as having the dorsal fin origin near the raid-point of the body, between the levels of the branchial aperture and the vent. Gymnothorax larvae are further characterized by Castle (1965) as having a series of paired somatic chroma- Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 125 tophores along the dorsal surface of the gut from the level of the gall bladder to the vent, an unpaired mid-dorsal series in front of the dorsal origin, and pigment on the spinal cord. Using these generalized larval descriptions of the various muraenid genera, recent workers have described a number of leptocephali species. These eels were mostly Caribbean and Indo-West Pacific forms* There are 25 known muraenid species from the eastern Pacific (Table 1). Of these, 15 are endemics distributed among ? genera. Nine species distributed among 4 genera with population centers in the Indo-West Pacific and West Pacific have successfully crossed the Bast Pacific barrier and become established along the west coast of the Americas (Ekman, 1953I Briggs, 1961, 1967). None of these is widespread and abundant along the mainland coast (Rosenblatt et al., 1972). The leptoeephalus stage of 4 of these species have been described! larvae of Echidna nebulosa (Ahl, 1789), Echidna zebra (Shaw, 1797), and EnchelvnaBsa canina (Quoy and Gaimard, 1824) have been described by Castle (19651 1966) and the larva of Gymno thorax undulatus was described by DJAncona (1928a-c, 1930a), Fowler (1956), and Klauswitz (1964). Until now no leptocephali have been identified and described for those morays endemic to the eastern Pacific. Following are descriptions of muraenid leptocephali col Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 126 lected off the west coast of the Americas# with identifica tions of adult species where possible* Collections Materials for this study were collected by and are presently housed at the University of Southern California (USC)• the University of California at Los Angeles (UCLA), Scripps Institute of Oceanography (SIO), the Los Angeles County Museum of Natural History (LACM), the National Oceanic and Atmospheric Administration (NOAA) at La Jolla, California, and the Academy of Natural Sciences of Phila delphia (ANSP). Methods and Materials Methods of measuring leptocephali and counting their myomeres follow Castle (19^3) and Eldred (1966), Leptocephali were examined with an American Optical dis secting microscope using both reflected and transmitted light* A polaroid filter was used to show various fea tures, including myomeres and fin rays. Measurements, in millimeters, were made with an ocular micrometer, a Helios dial micrometer, and a pair of fine-point dividers. In naming leptocephali, I have not followed established prec edents set by Lea (1913)# Brunn (1937), Castle (1963), Eldred (1966), and Blache (1971) who indicated the larvae of known adult species with the nominative — e.g., Lepto- ceohalus Gvrnnothorax mordax, or L* Gymnothorax mordax. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 127 In order to be consistent with the rules of scientific nomenclature, I have simply referred to larvae as the leptocephalus of a named species. Those larvae that could not be identified to the species level have been assigned to that genus with which they show closest affinity. The Leptocephalus of Gymnothorax dovii (Gunther, 18?0) (Pig. 15» Tables 9. 10, 11) Material examined The following material was examined (Table 9)* (1) USC collectionst 3 specimens, 59*5 mm to 85.0 mm TLt Velero IV stations 137^8 and 137^9. (2) UCLA collections* 2 specimens, 71*0 mm and 72,0 mm TLt UCLA stations W58-180 and W58-19^« (3) SIO collections* 13 specimens, 58.0 mm to 78,0 am TLt SIO station SCOT*T0*5801-81. Description The compiled measurements and meristic data for each of the 18 larvae appear in Tables 10 and 11. All the larvae were considered when describing pigmentation of these leptocephali. The cleft of the mouth reaches to the posterior margin of the eye. The anterior nostril is round and slightly tubular, the nasal capsule large and ovalt the posterior nare is oval and above the anterior margin of the eye. The eye is round, pigmented and surrounded by a fleshy margin. The eye diameter is one-half the snout Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 15. The leptocephalus of Gvrnnothorax dovii. USC 13749. 85.0 mm TL, 144 myomeres. Lateral view of (A) entire larva. (B) head. (C) caudal region, and (D) region of liver. Abbrevia tions 1 CH. chromatophoress GB, gall bladder1 I. intestinet LV. liverf PC. pyloric caecum1 VF, first vertical blood vessel. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 129 o| S o >' Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. L V G B PC Table 9« Collection data for larvae of Gymnothorax dovii. 130 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 10. Measurements of the leptocephali of Gymnothorax dovii. Figures appearing in parentheses after measurements are percentages of the total length. 132 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. © * :•* » HejH rl W o ° i oSi X f l V- 5= co o i CH 0 0 ^ 2 - 'vO r? ph o S c l CO ^ © « » ^ H T n i wg©3 f * . C O ©-:*■ CM g & § OlJ sco^ O^IH M jr. ^ H w 5o=<fc ri OO v - » s * VI ^ Vi © - 3 - VO vn ,- » VO CM »0 » - * Jf S s $ CO *-l \ R. Vi. vo ro cm Vi V*. V*. Vi V. © co « h c m . sf r vr> O - C M C M VO iH C M VO *h © Vi V *. V *. iH i - < >0 VO, tH © © *H tH a a a a CO Cv CO i - l f t i « ft £ > § z " S H H *3 H 3 " “ 3 g +> ® £ & r- 4 C 0 ® r ^ +> 0 Pt 1 ® ■H tJ 133 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Measurements SIO SIO SIO UCLA UCLA SIO Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. depth 2.7 2.5 2.8 Measurements SIO SIO SIO SIO SIO USC Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. depth 2.6 2.6 2.9 2.6 3.0 3-0 Table 11. Meristic counts of the leptocephali of Gvmno- thorax dovii. *a-d is the number of preanal myomeres minus the number of predorsal myomeres. ♦♦Damage to leptocephalus is too extensive to permit counts. 136 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. Meristic counts SIO SCOT:TOs 5801-81 (#11) use 137^9 (#2) SIO SCOT:TO: 5801-81 (#1*0 SIO SCOT:TO: 5801-81 (# 6) use 13748 SIO SCOT:TO: 5801-81 (#12) Total 148 145 148 147 142 145 Preanal 85 88 87 88 85 85 Postanal 63 57 61 59 57 60 Predorsal 23 22 21 19 20 18 *a-d +62 +66 +66 +69 +65 +67 Liver (position) Anterior margin 11 11 12 11 11 11 Posterior margin 21 20 18 19 21 18 Gall bladder (position) Anterior margin 18 19 17 17 19 17 Blood vessels (position) First artery 16 15 16 17 16 16 Renal artery 74 73 74 72 74 71 Renal-portal vein 80 81 indistinct 79 80 78 Teeth (number) Upper l-V-6 l-VI-3 ** l-V-6 l-V-5 i-v-/ Lower l-VI-4 l-VI-5 l-V-4 1-V-5 l-V-4 i-v-; Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. Meristic counts SIO SCOT:TO: 5801-81 (#7) SIO SC0T:T0s 5801-81 (#13) SIO SCOTsTOs 5801-81 (#10) UCLA W58-194 UCLA W58-180 SIO SCOT:TOs 5801-81 (#3) 147 144 145 146 88 87 87 86 59 57 59 60 ** 21 23 20 21 +67 +64 +68 +65 ** 12 10 10 10 ** 21 23 19 19 19 19 17 17 ** 17 16 15 11 ** 75 73 73 71 - 82 80 79 80 %omeres (number) Total Preanal Postanal Predorsal *a-d Liver (position) Anterior margin Posterior margin Gall bladder (position) Anterior margin Blood vessels (position) First artery Renal artery Renal-portal vein Teeth (number) Upper Lower 144 90 54 20 +70 11 18 16 14 75 82 l- V - 7 l-V-6 l-V-6 l- I V - 7 l-v-5 l-V-4 1-III-6 l-VI-4 lacking l-VI-4 l-VI-4 l-V-6 Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. Meristic counts SIO SCOTiTO i 5801-81 (#1) SIO SCOT«TO i 5801-81 (#9) SIO SCOT»TO« 5801-81 (#8) SIO SCOTiTO* 5801-81 (#5) SIO SCOTiTO 5801-81 (# 2) use 13749 (#1) l^yomeres (number) Total Preanal Postanal Predorsal •a-d Liver (position) Anterior margin Posterior margin Gall bladder (position) Anterior margin Blood vessels (position) First artery Renal artery Renal-portal vein Teeth (number) Upper Lower 151 148 149 147 148 144 86 89 90 88 90 87 65 59 59 59 58 57 21 21 21 20 20 20 +65 +68 +69 +68 +70 +67 11 8 12 12 9 9 21 19 22 19 19 18 18 16 19 18 17 17 16 13 16 16 14 17 75 76 75 74 76 72 & 73 (branchef 81 84 81 78 indistinct 81 L-Y-7 ** l-IV-6 l-V-5 l-V-4 l-V-4 L-VII-6 •* l-VI-4 l-V-6 1-VI-3 l-VI-4 140 length. The pectoral fin is minute (lacking in some specimens). Caudal fin rays number 3 + 2. There are 12 branchiostegal rays. The inconspicuous pigmentation formed of compact, rounded,chromatophores is as followsi Eleven to 39 surface and subsurface chromatophores (some diffuse) are scattered over the dorsal surface of the head. Some larvae have 2-3 deep chromatophores beneath the dorsal midline and medial to the nasal capsules. In the nasal capsule medial to the anterior nare are 1 to 5 chromatophores which may or may not be present. Eyes are pigmented in all specimens, and one shows a small patch of pigmentation in the postero- ventral region of the eye margin. There are 1-5 (usually 2 or 3) deep chromatophores on the posterior and ventral portion of the lower jaw, and there are usually 8-15 dark chromatophores scattered over the palate, but these may be fewer or even lacking. Inside the gill opening there are 1-3 chromatophores. One to 3 surface chromatophores occur in a vertical line ventral to the gill opening. Five to 20 chromatophores are over the heart region, while 8-20 surface chromatophores form an arc over the branchial region. There are 3-6 chromatophores on the rayeleneepha- lon, 1-2 always at the junction of the cerebellum and the myelencephalon and others in a cluster laterally and pos teriorly before the origin of the spinal cord. A series of 2 chromatophores per myomere are on the dorsal midline. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. from the vicinity of myomere 9 to the origin of the dorsal fin around myomere 20. A series of chromatophores, usually 2-3 per myomere, are along the ventral surface of the intestine anterior to the liver. The liver has many chro matophores on the ventral surface, from 3-10 per myomere. There is a series of 3-^ chromatophores per myomere along the dorsal surface of the intestine for its entire length posterior to the liver, and there is another series of 2-5 chromatophores per myomere along the ventral surface of the intestine posterior to the liver (in some specimens this series is interrupted by spaces of no pigment). A small cluster of chromatophores is found on the ventral surface of the gut at the vent in a number of specimens, and there is a series of 5-8 chromatophores per segment along the entire length on the ventral surface of the spinal cord. Rounded chromatophores are found at the ray bases along the entire length of the dorsal, anal, and caudal fins• Discussion Lepteeaphali in this assemblage cams from the v?es± coast of central Mexico and Chimbote, Peru. I feel certain that the 18 leptocephali belong to the same species, for they exhibit characteristic pigmentation not as yet ob served in any other leptocephalus. The chromatophores which occur on the myelencephalon (Pig. 15 and previously Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 142 described) always appear in the same arrangement whether the larva be from Peru or Mexico. Additionally, all speci mens exhibit the arrangement of chromatophores in an arc over the branchi&l region. These points, as well as the data presented in Tables 10 and 11, leave little doubt that these leptocephali are conspecific. Each larva displays pigmentation characteristic of the genus Gvmnothorax, i.e., chromatophores on the dorsal midline, spinal cord, intestine, and dorsal and anal fins. Other east Pacific Muraenidae (Echidna. Enchelycore. Enchelvnassa. and Muraena) are not known to possess pig mentation on most regions as described for these 18 larvae. Though no leptocephali have been described for species of Priodonophis. P. angusticeps is known only from Peru, and £• eouatorialis has never been collected south of Costa Ricai both are discounted as adult forms of these larvae.. Of the 11 species of Gymnothorax in the east Pacific, Gvmnothorax dovii is the only species in this genus with a geographical distribution extending from the Gulf of Cali fornia to Peru, including Clipperton Island and the Galapagos Archipelago. Not only do the collection loca tions for both adults and larvae overlap, but the verte bral number (141-151) and myomere counts (142-152) cor respond well also. From the information available and presented here, these leptocephali are assigned to Gymnothorax dovii. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 143 The Leptocephalus of Gymnothorax mordax (Ayres* 1859) (Pig* 16j Tables 12 and 13) Material examined The material examined was from the SIO collectionst 1 specimen* 76.4 mm TL» SIO station 60-323* Magdalena Bay. Baja California* 24° 35* N, 112° 4* W, taken on October 25. 1951* with a night light and dip net. Description This leptocephalus has already begun metamorphosis (Pig. 16). Measurements are presented in Table 12, meris- tic data in Table 13. The snout is blunt with a pronounced ventral pro trusion which gives the larva a definite beaked appearance. Teeth are absent. The cleft of the mouth reaches the posterior margin of the eye. The nasal capsule is large with the anterior nostril tubular and ovate. The posterior nostril is round with the aperture above the anterior mar gin of the eye. The eye is round and densely pigmented with black and has a narrow fleshy margin. The eye diam eter is less than one-half of the snout length. The pec toral fin is only a slight bud. Caudal fin rays are 3+2. There are approximately 350 dorsal fin rays and some 250 anal fin rays. The branchiostegal rays are indistinguishable. The inconspicuous pigmentation consists of small compact* rounded or elongate chromatophores and expanded Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 16. The leptocephalus of Gymnothorax mordax. SIO 60-323* ?6.4 mm TL. Lateral view of (A) entire larva* (B) head, (C) caudal region, and (D) region of liver. Abbreviations1 CH, chroma tophores s GB, gall bladders I* intestines LV» livers PC, pyloric caecums VF, first vertical blood vessel. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 145 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. C H L V G B PC Table 12. Measurements of the leptocephalus of Gymno thorax raordax. Figures appearing in paren theses after measurements are percentages of the total length. 146 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 147 Measurements (mm) SIO 60-323 Total length 76.4 Preanal length 44.2 (58 fa) Postanal length 32.2 (4295) Predorsal length 37.9 (5095) Dorsal-anal length 14.8 ( 695) Maximum depth 8.7 (11 Head length 4.0 ( 595) Snout length 1.2 Eye diameter 0.6 Post-cranial depth 2.6 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 13* Meristic counts of the leptocephalus of Gymno thorax mordax. *a-d is the number of preanal myomeres minus the number of predorsal myomeres. 148 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 149 Meristic Counts SIO 60-323 %omeres (number) Total 145 Preanal 75 Postanal 70 Predorsal 49 *a-d +20 Liver (position) Anterior margin 14 Posterior margin 22 Gall bladder (position) Anterior margin 21 Blood vessels (position) First artery 12 Renal artery 66 Renal-portal vein 72 Teeth (number) Upper none Lower none Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ones with a compact, minute, central spot surrounded by a diffuse ring of pigment (this type of chromatophore has previously been described for the genus by Castle, 1965)* In detail, the pigmentation is as follows * ~10 chromato phores are scattered over the palate and 2 deep chromato phores are on the postero-ventral portion of the lower jaw. Five chromatophores are anterior to the pectoral base and within the gill opening, while 22 chromatophores are scat tered over the heart region. There is a series of chroma tophores along the dorsal midline, before the origin of the dorsal fin, between myomeres 9 and 49 and another series (2-4 per myomere) along the ventral surface of the intes tine before the liver. Approximately 75 chromatophores are densely scattered over the ventral surface of the liver between myomeres 14 and 22. A series of 5-6 chromatophores per myomere is above the intestine from the liver to the vent. Also a series of chromatophores runs along the entire ventral and lateral surfaces of the spinal cord, and a series of elongate chromatophores is on the bases of the dorsal and anal fin rays. The eyes are pigmented. Discussion On October 25, 1951* a single metamorphosing lepto cephalus larva (SIO 60-323) was captured using a night light and dip net from a boat near Belcher Point, inside Magdalena Bay, Baja California, It is believed that this Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 151 specimen belongs to Gymnothorax mordax. It was collected along with four other leptocephali. These four, as well as two others collected on subsequent evenings, are much larger and have many more myomeres (167-176) than does the putative larva of G. mordax. Therefore these are inter preted as belonging to another muraenid species and are described later. The myomere count (145) of the SIO 60-323 lepto cephalus lies within the range of the adult G. mordax vertebral counts of 142-152 (Table 7). Additionally, it was collected within the known geographical distribution of this eel (Point Conception, California to Magdalena Bay, Baja California). This larva, with its characteristic anatomical features and disposition of chromatophores, is similar to those congeneric leptocephali described by Castle (1965), to G. undulatus and G. henaticus described by O'Ancona (1928a*75,82), and to leptocephalus larva IV described by Nair and Mohamed (1960*211). Also similar are those leptocephali identified as G. nigromarginatus (Eldred, 1969b), G. viclnua (Eldred, 1970a), G. moringa (Eldred, 1970b), G. funebris (Eldred, 1970a), and G. maderensis (Blache, 1971). Of the 25 currently known species of east Pacific Muraenidae distributed among 9 genera, the genus Gymno thorax is represented by 10 species (over 40# of the species in the family) (Table 1). Nine species of Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 152 Gymnothorax as well as those representatives of the remain ing 8 genera can be eliminated as possible adult forms of this leptocephalus either by geographical distribution of the species, vertebral counts, or by publsihed larval descriptions identified to spebies. Anarchias galapagensis and the b known species of Uropterygius (U. necturus, U. polystictus, U. schultzi. and U. tigrinus) can be discounted since larvae in these genera are quite different from other muraenids, having much reduced dorsal and anal fins (Castle, 1965» Eldred, 1968a- b). The larvae in the genus Echidna, unlike those of Gymnothorax. have pigmentation restricted to the head, with no pigment occurring along the intestine, spinal cord, or at the bases of the dorsal and anal fins (Castle, 1965* 1966), Echidna nebulosa and E, zebra have been described by Castle (1965, 1966). The former has 12^ myomeres, the latter, 135 (Table 7), D*Ancona (1928a) reported adults of E. nebulosa and E. zebra to have 122 and 135 vertebrae, respectively. These features positively eliminate these 2 species of Echidna as possible adult representatives of the SIO 60-323 larva. The third and last species represen tative of the genus in the east Pacific, E. nocturna. with a vertebral count of 118-122 (Table 7)» can be eliminated as well. Enchelvnassa canina. the only member of its genus Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 153 known from the eastern Pacific, has a described larval form with a myomere number of 143-145 (tentatively identi fied by Castle 1965# 1966, 1969). However, the pigmenta tion of its larvae does not resemble that of described Gymnothorax leptocephali. Moreover, the known distribution of E. canina (Table 1) does not overlap that of G. mordax. the former having been collected in the eastern Pacific only at Clipperton Island and Costa Rica. Three species of Muraena are known to occur along the west coast of Central Americai M. argue. M. clepsydra, and M. lentiginosa. All apparently occur from the Gulf of California to Panama and the Galapagos Islands. One, lentiginosa. has been collected at Magdalena Bay on the Pacific coast of Baja California. Descriptions of larvae belonging to this genus are unlike those for Gymno thorax (Grassi, 1910» Castle, 19651 Blache, 1963# 196?b, 1971), being more similar instead to leptocephali of Echidna and Enchelvnassa. Muraena argus and M. clepsydra have vertebral counts of 124 and 124-131, respectively (Table 7) and are not known to occur along the Pacific coast of Baja California. Thus these two species of Muraena are discounted as possible adult forms of the described larva. The third member of this genus, M. lentiginosa. has a range that overlaps that of G. mor dax. both having been collected at Magdalena Bay, Baja California. However, the radiographs of 10 individuals of Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 154 M. lentiginosa reveal that the number of vertebrae range from 114 to 118. This is far below the myomere number (145) of the larva identified as that of G. mordax. Con sequently JJ. lentiginosa is discounted as the adult form as well. Priodonophls eouatorialis has a vertebral count of 141-147 (Table 7) and is known to range from the Gulf of California to Costa Rica. Prlodonophis augusticeps has only been described from Peru. Both species are beyond the range limits of G. mordax. Of the 9 other species of Gymnothorax besides G. mordax known to occur along the west coast of North, Central, and South America, most can be positively elim inated as possible adult species of the SIO 60-323 larva on the basis of their geographic ranges and vertebral counts (Table 7)* Gymnothorax buroensis. a west Pacific moray with a vertebral count of 110-119. is only known in the east Pacific from Clipperton Island, Costa Rica, and Panama. The myomere number of the SIO 60-323 larva (145) lies within the Vertebral range of G. castaneus (138-145). However, G. castaneus has only been collected inside the Gulf of California, along the west coast of Mexico, and Panama. There is no published record of its capture south of Bahia Frailes (23° 24* N lat, 109° 24* W long) along the Baja peninsula in the Gulf of California, but it seems probable (John McCosker, personal communication) that it Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 155 occurs as far south as Cabo San Lucas (22° 5^' N lat, 109° 56* W long) just 30 nautical miles to the south. Even so, it is unlikely that its larva would be collected 160 miles to the north inside Magdalena Bay (24° 32* N lat, 112° 2* W long) on the Pacific side of the Baja California peninsula. Moreover, Fowler (1944) described a larva, Leptocephalus subfuscus. collected at Maria Madre Island (21° 36* N lat, 106° 36* W long) in the Tres Marias group, which I believe may be the leptocephalus of either G. cas taneus or G. panamensis. This problem is examined further in a later discussion. Gymnothorax dovii has a vertebral count of 141-151 and a broad geographical distribution, from the Gulf of California to Peru, including Clipperton Island and the Galapagos Islands. The myomere number of the G. mordax larva falls within the range of vertebrae counted for £• dovii. However, 18 larvae with myomere numbers that overlap the vertebral count of G. dovii have been collected within the known geographical range of G. dovii. These larvae* with respect to meristic data, are significantly different from the leptocephalus of G. mordax. and have already been described as belonging to G. dovii. Gymnothorax eurostus and Gymnothorax flavimarginatus are west Pacific species, the former occurring at Easter Island and Costa Rica, and the latter at Clipperton and Cocos Islands, Costa Rica, and Panama. Their vertebral Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 156 counts (Table 7) and geographical distribution are suf ficient to discount each as possible adult forms of the SIO 60-323 larva. Gymnothorax nanamensis is known to occur at Mag dalena Bay, Baja California along with G. mordax. One specimen of G. nanamensis was even collected by C. L. Hubbs at Guadalupe Island, far to the north. Randall and McCosker (in press) have determined that the vertebral number of G. -panamensls in the Gulf of California and at Cabo San Lucas, Baja California, ranges from 123-128 (Table 8). This is far below the vertebral range of G. mordax. Gymnothorax nictus and Gymnothorax undulatus are Indo-Pacific morays, but the former has been collected at Clipperton Island and the latter at Costa Rica and Panama. Gymnothorax weineri is an east Pacific endemic known only from Peru. Additionally, leptocephali collected off Peru are described here as belonging to G. weineri. Either the geographical range of each of these 3 species (Table 1), or their respective number of vertebrae (Table 7), place them outside of the range of the larva described here as that Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 15? A Leptocephalus Tentatively Identified As Gymnothorax plctua (Ahl, 1789) (Pig* 17l Tables 14 and 15) Material examined The material examined was from the UCLA collectionst 1 specimen* 63.0 mm TLi UCLA station W56-237* Clipperton Island* 10° 18* N lat, 109° 13* W long, taken on October 24* 1956* with Nox-fish and a dip net. Description At 63*0 mm TL, this leptocephalus has already begun metamorphosis (Pig* 17)• Measurements appear in Table 14 and meristic data in Table 15* The snout is extremely blunt and rounded* The cleft of the mouth reaches to the posterior margin of the eye. The anterior nostril is tubular and ovate* the nasal capsule large* and the oval posterior nare is above the anterior margin of the eye* The darkly pigmented* round eye is surrounded by a narrow fleshy margin* The eye diameter is two-thirds the snout length. Two supraorbital, 1 ethmoid* 4 infraorbital* and 6 mandibular pores were observed along the cephalic lateral- line system. No branchial pores were found. The pectoral fin is minute. Caudal fin rays number 3+2, Branchio- stegal rays are indistinguishable* and the dorsal and anal fin rays show heavy damage which prevents counting. The inconspicuous pigmentation* formed of compact, rounded chromatophores is as followst There are about 6 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 17. A leptocephalus tentatively identified as Gymnothorax oictus. UCLA W56-237* 63.O mm TL, Lateral view of (A) entire larva* (B) head, (C) caudal region* and (D) region of liver. Abbreviations* CH- chromatophores) GB, gall bladder) I, intestine) LV, liver) PC, pyloric caecum) VF, first vertical blood vessel. 158 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 159 U| S o Q| Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. C H Table 14. Measurements of that leptocephalus tentatively identified as Gymnothorax rictus. Figures appearing in parentheses after a measurement are percentages of the total length. 160 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 161 Measurements (mm) UCLA W56-237 Total length 63.0 Preanal length 43.0 (68 96) Postanal length 20.0 (32-*) Predorsal length 39.0 (6296) Dorsal-anal length 4.0 ( 696) Maximum depth 6.2 (1096) Head length 3.4 ( 598) Snout length 0.9 Eye diameter 0.6 Post-cranial depth 2.0 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 15. Meristic counts of that leptocephalus tenta tively identified as Gymnothorax rictus. *a-d is the number of preanal myomeres minus the number of predorsal myomeres. 162 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 163 Meristic Counts UCLA W56-237 Myomeres (number) Total 133 Preanal 79 Postanal 5k Predorsal 73 *a-d +6 Liver (position) Anterior margin 13 Posterior margin 23 Gall bladder (position) Anterior margin 23 Blood vessels (position) First artery 12 Renal artery 65 Renal-portal vein ?k Teeth (number) Upper none Lower none Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 164 minute chromatophores on and below the surface near the anterior nostril. There is one deep chromatophore on the lower jaw postero-ventrally. Three subsurface chromato- phores are found in a vertical line inside the gill open ing. There are 9 chromatophores scattered over the heart region, and there are 1-2 faint, dark chromatophores on the myelencephalon. A series of 1-2 chromatophores per myo mere is on the dorsal midline from myomeres 5 to 73 before the origin of the dorsal fin. There are 4 along the ventral surface of the intestine anterior to the liver and about 18 chromatophores (0-3 per myomere) along the ventral surface of the liver. A series of 4-5 per myomere runs along the entire length of the dorsal surface of the intes tine from the liver to the vent. Another series of about 6 chromatophores per myomere runs the entire length of the spinal cord. There are rounded chromatophores at the ray bases along the entire lengths of the dorsal and anal fins. The eyes are pigmented. Discussion This ieptoeephalus displays pigmentation character istic of the genus Gvmnothorax, i.e., chromatophores on the dorsal midline, spinal cord, intestine, and dorsal and anal fins. Of the five known species of Gymnothorax from Clip- perton Island, G. buroensis, G. dovii. G. flavimarginatus. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 165 6. panamensis. and G. pictus. only 2 have vertebral ranges near that of the 133 myomeres described for the larva (Table 7)* X-rays of specimens of G. flavimarginatus from Clipperton Island show from 134 to 138 vertebrae; G. pictus from the same locality has from 127 to 133 vertebrae. Until more information can be gathered about east Pacific muraenid adults and leptocephali, this larva cannot be positively identified. However# because its myomere num ber falls within the vertebral range of G. pictus. this larva is tentatively assigned to that species. The Leptocephalus of Gymnothorax weineri Sauvage, 18S3 (Pig. 18; Tables 16 and 17) Material examined The following material was examined; (1) SIO col lections; 1 specimen, 74.0 mm TL; SIO station Shellback SB-177. Galapagos Islands, 2° 07' N, 89° 12* 30" W; taken with a night light and dip net on August 7, 1952. (2) UCLA collections; 2 specimens, 60.0 and 88.0 mm TL; UCLA station W58-102, Bahia Callas, Peru, 12° 04' 30" S, 77° 10® h’g taken with a night light and dip net, January 24, 1958. Description Measurements and meristic data for the larvae appear in Tables 16 and 17. respectively. The snout is blunt with a ventral protrusion of the upper lip which gives the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 18. The leptoeephalus of Gymnothorax weineri. UCLA W58-102, 88.0 mm TL. Lateral view of (A) en tire larva. (B) head. (C) caudal region, and (D) region of liver. Abbreviations* CH. chro matophores t GB, gall bladdert I, intestinet LV, liveri PC, pyloric caecumt VF, first vertical blood vessel. 166 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 167 <\ Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. C H L V G B PC Table 16. Measurements of the leptocephali of Gvmnothorax weineri. Figures appearing in parentheses after measurements are percentages of the total length. 168 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 169 Measurements (mm) UCLA SIO UCLA W58-102 Shellback W58-102 (#1) SB-177 (#2) Total length 60.0 74.0 88.0 Preanal length 44.0 (73*) 50.0 (68*) 62.0 (71*) Postanal length 16.0 (27%) 24.0 (32%) 26.0 (30*) Predorsal length 23.0 (38%) 28.0 (38%) 35.0 (40*) Dorsal-anal length 21.0 (35%) 24.0 (32%) 27.0 (31*) Maximum depth 7.6 (13%) 13.0 (18%) 14.0 (16*) Head length 4.1 ( 7%) 3.8 ( 5%) 4.4 ( 5%) Snout length 0.6 1.3 1.2 Eye diameter 0.6 0.5 0.6 Post-cranial depth 3.0 2.1 3.3 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 1?» Meristic counts of the leptocephali of Gymno- thorax weineri. *a-d is the number of preanal myomeres minus the number of predorsal myomeres. 170 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1?1 Meristic Counts UCLA W58-102 (#1) SIO UCLA Shellback W58-102 SB-177 (#2) Myomeres (number) Total Preanal Postanal Predorsal *a-d Liver (position) Anterior margin Posterior margin Gall bladder (position) Anterior margin Blood vessels (position) First artery Renal artery Renal-portal vein Teeth (number) Upper Lower 141 88 53 47 +41 10 20 17 14 74 79 & 82 (branches) none none 143 86 57 44 +42 19 16 16 72 77 l-VII-6 l-VII-5 141 88 53 46 +42 10 19 17 13 73 77 none none Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 172 larva a beaked appearance. Teeth are absent. The cleft of the mouth reaches to the posterior margin of the eye. The large nasal organ bears a tubular oval anterior nostril. The posterior nostril is round and above the anterior mar gin of the eye. The eye is round and pigmented black with a narrow fleshy margin. The eye diameter is one-half the snout length. In the cephalic lateral-line system there are 2 supraorbital, 1 ethmoid, ^ infraorbital, and 6 man dibular pores. No branchial pores were observed. Pectoral fins are lacking. There are 3 + 2 caudal fin rays and 9 branchiostegal rays. Generally chromatophores are brown and inconspic uous, either compact or diffuse, and rounded or elongate. The head is unpigmented (except for the eyes and palate) in the large larva. However, the smallest larva has 3 deep chromatophores on the dorsal surface of the head poster iorly. There may or may not be 2 deep chromatophores on the posterior end of the lower jaw, 6 chromatophores scat tered on the palate, 1-2 deep chromatophores near the gill opening, 2-3 surface chromatophores over the branchial region, and 1-2 pigment spots on the myelencephalon. All three larvae have pigment spots (7-12) scattered over the heart region. There are 13-21 distinct, reddish chromato phores, 1-2 per myomere, along the ventral surface of the liver. Along the dorsal surface of the intestine posterior to the liver and extending to the anus there is a series of Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 173 2-3 small, reddish chromatophores per myomere. There is also a series of 1 chromatophore per myomere along the entire length of the spinal cord. Additionally, there is a series of either elongate or rounded brown chromato phores at the ray bases along the entire length of the dorsal, anal, and caudal fins. The eyes are black. Ho pigmentation was observed on the dorsal midline before the origin of the dorsal fin, nor along the ventral surface of the intestine either anterior or posterior to the liver. Discussion In August of 1952, a leptocephalus was collected in a trawl near the Galapagos. Six years later 2 more larvae were collected off the dock at Bahia Callas, Peru, using a night light and dip net. It is believed these are larvae of the moray Gvmnothorax weineri. a muraenid known to oc cur in Peruvian waters (Hildebrand, 19^6). Of the 26 muraenid species in the east Pacific, only 3 (Gvmnothorax dovii, Gymnothorax weineri, and Priodonophls angusticeoe) have been collected off Peru. G. dovii appears t© be one of the fes? in the family that has a: broad geographical distribution in the east Pacific. Adults of this species have been collected from the Gulf of California to Peru, including Clipperton Island and the Galapagos Archipeligo (Table 1). A series of similar larvae collected at various stations distributed along the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 174 coast from Central to South America were previously de scribed here as the leptocephali of Gvmnothorax dovii. No descriptions of the leptocephali of Priodonophis are to be found in the literature. Lacking larval descrip tions of the aforementioned genus with which to compare the present leptocephali, I considered vertebral counts from adults of P. angusticeps and Gvmnothorax weineri. It was determined from the X-ray of a single speci men of Priodonophis angusticepg that the animal possessed 138 vertebrae. Until additional P. angusticeps specimens can be examined, it remains questionable whether its verte bral range would include the number of myomeres exhibited by the UCLA W58-102 and SIO Shellback SB-177 larvae. Specimens of Gvmnothorax weineri examined have vertebrae ranging from 134 to 142. Two of the leptocephali have myomere numbers that fall within this vertebral range, and the myomere count of the third is only one removed. Prom previous descriptions of other Gvmnothorax larvae (cited earlier in the discussion section of the Gvmnothorax mordax leptocephalus description) certain characteristic pigmentation is observed. The larvae ten tatively described here as belonging to Gvmnothorax weineri agree with this pattern except in one respect — there is no pigmentation on the dorsal midline before the origin of the dorsal fin. I do not feel this is sufficient to exclude these larvae from the genus Gvmnothorax at the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 175 present. As more muraenid leptocephali are identified to the species level 1 would expect more variability in these generic characters to be recognised. Though Gvmnothorax weineri is currently known only from Peru, one of the larvae believed to belong to this species is from the vicinity of the Galapagos Archipeligo. Pelagic larvae like leptocephali are known to be carried long distances by ocean currents (Castle. 1968i Blache. 1971). It is conceivable that the SIO Shellback SB-177 larva was carried to the Galapagos by the Peru Current which flows from south to north along the west coast of South America. The coastline of Peru, which angles from the southeast to the northwest, directs the current along a similar course. The Galapagos lie directly in the path of the Peru Current as it leaves the mainland coast near Punta Parinas (^5° S lat) flowing northwest. Moreover, in light of this information (and if these larvae are truly those of Gymnothorax weineri) it is reasonable to expect that G. weineri will eventually be found at the Galapagos when additional collections are made. An Unidentified Gvmnothorax larva (117 Myomeres) (Pig. 19* frables 18 and 19) Material examined The material examined was from the USO collections! 1 specimen, 55.0 mm TLt Velero IV station 137^9. 21.5 miles, 230° T from Punta Farallon Light, Mexico* Issacs- Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 19. An unidentified Gvmnothorax larva* (117 myo meres)* USC 137^9# 55»0 mm TL. Lateral view of (A)» entire larva* (B) head* (C) caudal region* and (D) region of liver. Abbrsvia- tionsi CH» chromatophores1 GB. gall bladderi I* intestine* LV, liver* PC, pyloric caecum* VF, first vertical blood vessel. 176 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 177 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LV GB Table 18. Measurements of an unidentified Gvmnothorax larva (117 myomeres). Figures in parentheses following measurements are percentages of the total length. 178 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 179 Measurements (mm) USC 137^-9 Total length 55.0 Preanal length 33.5 (61*) Postanal length 21.5 (39*) Predorsal length 23.5 m % ) Dorsal-anal length 6.7 (12*) Maximum depth 7 A (13*) Head length 3.1 ( 6*) Snout length 0.9 Eye diameter (horizontally) 0.6 Post-cranial depth 2.9 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 19. Meristic data for the unidentified Gvmnothorax larva (11? myomeres). *a-d is the number of preanal myomeres minus the number of predorsal myomeres. 180 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 181 Meristic Counts USC 13749 Myomeres (number) Total 117 Preanal 59 Postanal 58 Predorsal 46 *a-d +13 Liver (position) Anterior margin 10 Posterior margin 18 Gall bladder (position) Anterior margin 17 Blood vessels (position) First artery 15 Renal artery 51 Renal-portal vein 55 Teeth (number) Upper l-V-4 Lower l-V-6 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 182 Kidd midwater trawl (IKMWT) from 19° 05* 30- N, 105° 13' 15" W to 19° IV 00” N, 105° 32* 00" W, towed 45 minutes at a depth of 800 ft., and 45 minutes at 1800 ft., January 17, 1970. Description Unlike many other larvae described here, this lepto- cephalus has not yet begun metamorhposis (Fig. 19). Measurements are given in Table 18 and meristic data ap pears in Table 19« The snout is short and pointed. The cleft of the mouth reaches to the posterior margin of the eye. The anterior nostril is tubular and ovate, the nasal capsule large, and the oval posterior nare is above the anterior margin of the eye. The darkly pigmented, round eye is surrounded by a fleshy margin. The eye diameter is two-thirds the snout length. The cephalic lateral-line system bears two supraorbital, one ethmoid, four infra orbital, and six mandibular pores. No branchial pores were observed. The pectoral fin is minute. Caudal fin rays are 3+2. Branchiostegal rays number about 9. Chromatophores are generally very dark, either round or elongate, and distributed as followsi 5 chroma tophores are found posteroventrally on the lower jaw. There are 19 black chromatophores scattered over the palate as well as 2 deep chromatophores near the gill opening. There are 15 scattered over the heart region, and one Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 183 faint chromatophore is on the cerebellum and 4 on the myel- encephalon (brain chromatophores were present only on the right side). There are 8 chromatophores along the dorsal midline between myomeres 15 and 28. A series of 1-2 per myomere runs along the ventral surface of the intestine anterior to the liver. There are 2-4 chromatophores per myomere on the ventral surface of the liver, as well as a series of 3-4 chromatophores per myomere extending along the entire length of the dorsal surface of the intestine posterior to the liver. There are 2 chromatophores per myomere along the ventral surface of the spinal cord throughout its length, dark and slightly elongate chroma tophores at the base of each of the dorsal and anal fin rays, and 1 spot on each of 2 caudal rays. Eyes are pig mented. Discussion This letocephalus, collected in a trawl off the coast of Mexico, was the only larva examined with a relatively low number of myomeres (117). Pour east Pacific muraenid species in 3 genera have vertebral ranges near or including the myomere number of this leptocephalus (Table 7). These 4 species are Echidna nebulosa. E. noctuma. Gvmnothorax buroensis. and Muraena lentiginosa. As pre viously discussed, leptocephali described as belonging to Echidna (Castle, 1965. 1966) and Muraena (Grassi, 1910» Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Blache, 1963» 196?b, 1971i Castle, 1965, 1966) have pig ment patterns unlike that of Gvmnothorax larvae (Castle, 1965* Blache, 196?e, 19711 Eldred. 1969b, 1970a-c). Though this eliminates Muraena and Echidna from consideration as possible adult forms of this leptocephalus, the larva can not yet be positively identified to the species level. In the east Pacific Gvmnothorax buroensis is the only known species of moray with a vertebral range (110-119) that includes the myomere number (117) of this leptocephalus. However, G. buroensis has only been collected at Clipperton Island, Cocos Island, Isla del Cano, Isla Murcielago. end Islas Secas, Gulf of Chiriqui, Costa Rica (Rosenblatt et al.. 1972). This places the collection site approximately 1500 miles northwest of known Costa Rican adults and 700 miles north of the Clipperton Island population. Current patterns (Sverdrup et al., 19^2) off the west coast of Mexico are not likeiy to carry a larva from either Clip perton Island or Costa Rica to the area of capture. Either the geographical distribution of G. buroensis is broader than presently recorded or anbther, as yet uncollected moray is to be found along the west coast of Mexico. If the latter is the case, it is possible that the eel is either new to science or a known Indo-Pacific species yet to be collected in the east Pacific. Whatever the case, it is obvious that further collections are necessary in this region before a conclusive statement can be made as to the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 185 identity of this leptocephalus. Additional leptocdphali collected from other locations might also lead to a species identification and should be kept in mind when examining new specimens of leptocephali. Meanwhile, this larva is assigned to the genus Gymnothorax. Ten Large, Unidentified Gymnothorax Larvae (167-176 Ityomeres) Fig. 20* Tables 20, 21, and 22) Material examined Material from the following collections was examined (Table 20)i (1) ANSP collections* 1 specimen, 142.0 mm TL, ANSP #70117. (2) UCLA collections* 1 specimen, 149.0 mm TL, UCLA station W53-242. (3) SIO collections* 1 specimen, 164.0 mm TL, SIO station 64-903* 1 specimen, 131.0 mm TL, SIO station 60-322* 2 specimens, 117.0 and 135.0 mm TL, SIO station 60-307* 4 specimens, 117.0 - 140.0 mm TL, SIO station 60-323. Description Compared to all other muraenid larvae described in the literature, these are extremely large. Each has begun metamorphosis (Fife. 20) and some even have adult-type teeth. Tables 21 and 22 list the measurements and meristic counts for each leptocephalus examined. The description of pigmentation summarizes the chromatophore distribution on all larvae observed. The snout is short and rounded with a ventral pro- Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 20. A large unidentified Gymnothorax larva (173 myomeres), SIO 60-322, 131.0 mm TL. Lateral view of (A) entire larva, (B) head, (C) caudal region, and (D) region of liver. Abbrevia tions! CH, chromatophoresi GB, gall bladder? I, intestinei LV, liver? PC, pyloric caecum, VF, first vertical blood vessel. 186 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 187 s o Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LV GB PC Table 20* Collection data for specimens of an uniden tified species of Qymnothorax larvae with 16?-1?6 myomeres* 188 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. c*o •H O P+3 is to !&+» ■ P P x: - h + > p x:*h M.TJ •H C «8 t*+ > tjL-P •HO -HO H C riC +* P -P P x:-h j p *h bit! W'O C«8 C «8 tl£-P •H o f H C + = P ■£•0 •H c-» 189 W)4* •H O i H C + > P J C *H u « •H G«» S3 C O • o • P o gn ® d © 1-40 O •§ © « H b D -r o J cd ©at ©as ® JJ o3 l, pq s m g n m s m c m to • • WtM O R»*H P O H a 3 c a 0 ^ 0 P H §s < o- O M I C O O O I tO'O §? \r\e P>*H H O o s *H H O H CM Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 21. Measurements of the leptocephali of an uniden tified species of Gymnothorax (167-176 myo meres). Figures appearing in parentheses after measurements are percentages of the total length. 190 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 191 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 192 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 22. Meristic counts of the leptocephali of an unidentified species of Gvmnothorax (167-176 myomeres). *a-d is the number of preanal myo meres minus the number of predorsal myomeres. ♦♦Structure is indistinguishable. 193 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. Meristic Counts SIO 60-323 (#1) Nfyomeres (number) Total 167 Preanal 105 Postanal 62 Predorsal 32 *a-d +73 Liver (position) Anterior margin 10 Posterior margin 24 Gall bladder (position) Anterior margin 22 Blood vessels (position) First artery 15 Renal artery 91 Renal-portal vein 95 Teeth (number) Upper lacking Lower lacking SIO SIO SIO 60-307 60-322 60-323 (#2) W ) SIO 60-307 (#1) 175 173 176 110 111 112 65 62 64 35 33 35 +75 +78 +77 11 11 12 25 21 23 23 19 21 14 16 13 90 93 100 100 104 107 (few adult- lacking lacking type teeth lacking lacking posteriorly) 175 110 65 35 +75 12 26 24 14 89 100 lacking lacking Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. Meristic Counts SIO 60-323 (#2) Myomeres (number) Total 175 Preanal 111 Postanal 64 Predorsal 34 *a-d +77 Liver (position) Anterior margin 14 Posterior margin 25 Gall bladder (position) Anterior margin 22 Blood vessels (position) First artery 15 Renal artery 91 Renal-portal vein 98 Teeth (number) Upper lacking Lower lacking SIO ANSP UCLA SIO 60-323 7011? W53-242 64-903 m ) 176 176 160 176 110 108 106 111 66 68 63 65 3 4 3 3 3 3 3 5 +76 +75 +73 +76 13 10 9 12 24 19 25 22 24 16 ** 17 18 91 94 ** 93 104 98 ** 105 lacking lacking (adult type)(adult type) lacking lacking (adult type)(adult type) 196 trusion of the upper lip which gives the larva a beaked appearance. The cleft of the mouth reaches to the poste rior margin of the eye. The large, oval nasal organ bears an anterior nostril which is oval and tubular and an oval posterior nare above the anterior margin of the eye. The eye is darkly pigmented and round with a fleshy margin. The eye diameter is two-fifths the snout length. The cephalic lateral-line system includes 2 supraorbital, 1 ethmoid, 4 infraorbital, and 6 mandibular pores. No branchial pores were found. The pectoral fin is minute and the caudal fin is rounded. Branchiostegal rays are 9 in number. Some variation in chromatophore pattern and distri bution was noted on these larvae. Chromatophores are generally dark when compact, reddish when diffuse, and round except at the bases of the dorsal and anal fin-rays where they are elongate. Half of the specimens examined have from 10-29 chromatophores on the dorsal surface of the head, while the other half had no pigmentation in this region. Pigmentation may or may not occur inside the nasal capsule. There are usually at least a few chroma tophores on the posteroventral part of the lower jaw. All larvae have many chromatophores (20-60) scattered over the palate. Two chromatophores inside the gill opening and several in a vertical line ventral to it may or may not be present. From 8-23 chromatophores may be found scattered Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 197 over the heart region. Chromatophores sure also sometimes found along the pharynx. A few larvae show small chroma tophores on the upper lip and snout anteriorly. Generally* the larvae sure too dense to observe stny pigmentation on the brain. However* 1 specimen has 25 chromatophores scattered over the dorsal surface of the cerebellum* Occasionally, 1 to several dark chromatophores csun be seen on the myel- encephalon* All larvae have a series of 1-2 chromatophores per myomere along the dorsal midline beginning between myomeres 3 and 14 and extending nearly to the origin of the dorsal fin around myomere 34. Most specimens have no pigmentation along the ventral surface of the intestine anterior to the liver, but some have from 2-6 chromato phores distributed sporadically along this short distance. Almost all larvae have 2-3 chromatophores per myomere along the ventral surface of the liver, but some have fewer than this or show pigmentation over only part of the distance. Each larva has a series of 1-4 chromatophores per myomere distributed along the length of the dorsal surface of the intestine posterior to the liver and a similar series of 1-2 chromatophores per myomere along the length of the ventral surface of the intestine posterior to the liver. Each larva bears one faint chromatophore on either side of the ventral aspect of the spinal cord along its entire length. All leptocephali have elongate chroma tophores at the base of each of the dorsal and anal fin- Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 198 rays* and some have chromatophores at the bases of the caudal fin rays. Discussion Seven of these leptocephali were collected inside Magdalena Bay on the Pacific coast of Baja California! one came from near Cabo San Lucas* another from the Gulf of California* and one* the paratype of Fowler’s Lepto- cephalus subfuscus. from Islas Tres Marias. These larvae have a total number of myomeres ranging from 167 to 1?6. Of the 21 species of Muraenidae in the east Pacific [jthe genera Anarchias and Uropterygius are excluded for reasons stated elsewhere (p. 124 ]Q, none has a vertebral count approaching that of the myomere number found in these larvae (Table 7)« On the other hand, these leptocephali do have a pigmentation pattern characteristic of Gymno- thorax. The occurrence of a number of these larvae in the same general area suggests that there exists along the west coast of Mexico, in the Gulf of California, and along the southern end of the Pacific coast of the Baja Peninsula, a moray eel either new to science or a known species, probably Indo-Pacific, yet to be collected in the eastern Pacific. Future collections from this region should produce the adult form of this leptocephalus• When discovered, it will likely prove to be a member of the genus Gvmnothorax. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 199 Leptocephalus aeeipiter Fowler, 1938 Leptocephalus aeeipiter. collected in the Galapagos Archipeligo, was recognized as belonging to the family Muraenidae by Castle (1969). This leptocephalus was de scribed by Fowler (1938) on the basis of two specimens, ANSP #68298 and ANSP #68299. 67 mm and 66 mm TL, respec tively. The total myomeres are given as 98 or 110, the preanal myomeres as 48 or 50, and the postanal myomeres as 58 or 60. It appears as if the number 58 is incorrect and should have been 50 instead. This would make possible a combination of preanal and postanal counts with a sum of 98. No such sum is possible with the data given in the original description. Fowler further describes the larvae as lacking pig mentation except for a "few dark pigment dots on chest be low head" which is analogous to surface chromatophores ventrally over the heart region. From this meager informa tion and considering that described leptocephali of both Muraena and Echidna lack pigmentation along the dorsal and anal fins, I suggest that these larvae probably belong to one of these genera. However, reference to Tables 1 and 7 shows that no species with this vertebral range is known from the Galapagos. Two explanations for this observation are possible. As observed by Randall and McCosker (in press) the vertebral number may vary considerably with changes in Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 200 latitude. Table 8 shows such a change in the vertebral number of Qvmnothorax panamensis as observed by them. It is possible that one of the known species of muraenids from the Galapagos has a different number of vertebrae than recorded on Table 7. To date, species of Echidna have not been collected at the Galapagos. Of the 3 east Pacific species of Muraena. all have been collected at the Gala pagos. Specimens of M. clepsydra from the Galapagos show a vertebral number consistent with the figures given on Table 7» Muraena argus and M. lentjginosa remain to be checked. Enchelvcore. as described by Blache (1971), also has no pigment at the base of the dorsal and anal fin-rays. X-rays of specimens of Enchelvcore octavianus from the Gulf of California show a vertebral range of 1^2-144. Though it should not be ruled out as an adult form of L. aeeipiter until radiographs are made of specimens from the Galapagos Islands and the vertebrae counted, I am doubtful that such a large change in vertebral number could be expected. The second possibility is that there is a species of moray at the Galapagos Islands that has not as yet been collected in the east Pacific. Either of these explana tions seems possible. However, until further collections are made in the Galapagos Islands and/or vertebral counts are recorded from specimens of morays collected there, little further speculation can be made as to the adult form of £. aeeipiter. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 201 Leptocephalus subfuscus Fowler, 1944 Castle (1969) recognized Leptocephalus subfuscus Fowler, collected at Islas Tres MSrias, Mexico, as belong ing to the family Muraeniaae. In reviewing Fowler's description of this larva a discrepancy was discovered in the myomere counts. The error lies either in the enumera tion of the total myomeres (138) or in the calculation of the preanal (82) and postanal (46) myomeres, the sum of which is 128, In describing L. subfuscus. Fowler obviously made an error of 10 myomeres. Without examining the holo- type it is impossible to determine whether this error lies in the total myomere count, the preanal, or postanal myo mere figures. Moreover, though Fowler (19^) stated that the para- type is the same as the holotype, I have examined the para- type (ANSP #70117) and found it to have 1?6 myomeres. It is significantly different from his description for Lepto cephalus subfuscus in many other ways as well. This larva, ANSP #70117* is redescribed here along with a number of other leptocephali. It is very similar to those larvae previously described as Gymnothorax sp, with a myomere range of 167-176, and therefore it has been included with this group. Nevertheless, a number of problems remain. However, until I can examine the holotype, none of these can be resolved. Assuming that the holotype of L, sub fuscus does, in fact, have 128 or 138 myomeres, and that Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 202 the paratype only was mislabeled or misidentified, then some speculation can be made as to the adult form of L. subfuscus. Even though the correct myomere figures are in doubt, L. subfuscus appears to be sufficiently different from dther leptocephali described herein to be a larval form of yet another species of muraenid. The identification of L. subfuscus to the species level* of course* depends upon the true number of myomeres, 128 or 138. If the actual number is 138 then I suggest that L. subfuscus is the larva of Gvmnothorax castaneus. vertebrae 138-14-5 (Table 7). This is the only known species of moray occurring within 500 miles of Islas Tres Marias whose vertebral count over laps that of L, subfuscus. If the actual myomere number is shown to be 128, then either of two additional species are passible adult forms of this larva* Gvmnothorax panamensis from Islas Tres Marias with 128-131 vertebrae (Randall and McCosker, in press), and Muraena argus from the Gulf of California with 124 vertebrae. Additional radiographs would provide a vertebral number range which might encompass the lower number of myomeres (128) attri buted to JL. subfuscus. However, species of larval Muraena described so far by Grassi (I896, 1897* 1915). Schmidt (1906, 1912, 1913). Bertin (1926), Pish (1927), D»Ancona (1928a,e, 1930. 1931). Ford (1931). Blache (1963. 1967b, 1971). and Castle (1965) have no pigmentation on the dorsal. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 203 caudal, or anal fins* The remainder of Fowler's descrip tion (19^*389) states there is no pigmentation except for a "narrow dark brown edge of the confluent dorsal and anal fins," If he is referring to small, elongate chromato phores at the bases of the dorsal, anal and caudal fin rays, as those found in some larvae described here and by Eldred (1969b, 1970a-b) and which could appear as a narrow pigmented line under low magnification, then I suggest this larva could be either that of G. castaneus or G. oanamensia Positive identification of this leptocephalus must await that time when the question concerning its actual myomere number can be determined and a more complete de scription Compiled, Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER VI SUMMARY AND CONCLUSIONS Although the California moray eel, Gvmnothorax mor- dax. is common in subtidal rocky reefs south of Point Con ception, California, and around the Channel Islands south to Magdalena Bay, Baja California, information regarding the biology of this fish is almost non-existent. This study was directed at contributing to the knowledge of £• mordax. A tagging study, using a specially developed, but inexpensive, tag and tagging gun was carried out in order to determine various aspects of population dynamics. Of 116 eels initially tagged, 6 were recaptured in traps and 7 were reobserved while diving. These morays were at large from 1 to 96 days after tagging. Growth rates compared favorably with expected values. Home ranges and territor ial behavior were not demonstrated, although large eels (> 1000 mm TL) remained longer in an area than smaller morays. The mean distance moved for eels less than 1000 mm TL was 1.7 m/day, whereas eels longer than 1000 mm TL moved only 0.3 m/day • It is possible that the larger morays establish territories while smaller ones are con- 204 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2 05 tinually immigrating to and emigrating from any given region. A population census was carried out on selected areas in Big Fisherman Cove, Santa Catalina Island, The estimates of density (1 eel/9m2) and standing crop (0.20 kg/m2) of this temperate eel were found to be sim ilar to some of the values found by various workers for tropical species of morays. Gymnothorax mordax maximally utilizes those resources available to it and for which there is no competition from other muraenids, a factor most likely responsible for the high calculated biomass of G. mordax. An activity-monitoring study was carried out on a small group of morays over a ^5“day period under natural light conditions. The California moray eel was shown to be strongly nocturnal with 87# of the total activity occur ring between sunset and sunrise. The activity level increased gradually from 3# between 1700-1800 to a maximum of 11# between the hours of 2200 and 2300. From this per iod until dawn, the percentage of hourly activity steadily decreased. Mean, diurnal, hourly activity levels were generally less than 1#. These observations compared favor ably with those made by divers in the field during both light and dark periods. Food and feeding behavior of G. mordax was studied. Of the morays with identifiable material in the gut, 35# had Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 206 eaten crustaceans* 3995 had consumed cephalopods, and byfo had ingested fishes under natural conditions. That this eel prefers fishes as food was indicated hy the large number of them consumed while both predator and prey were in the trap. Fishes eaten by the moray during entrapment were considered separately from food items consumed by the moray naturally. A general change was observed in the size of the prey with increasing size of the predator. A food index, an indication of feeding specialization, was cal culated for G. mordax as well as for several tropical morays. The food index values for each were similar and reflected these fishes' utilization of the same prey categories. Length-weight values were plotted for 70 males and 50 females. A student's t test was carried out on the pooled variances obtained from the calculated regression slopes for each group. It was determined that length-weight relationship between males and females is significantly different (p = .001). Nevertheless, accurate determina tion of the sex of an eel remains a difficult task without dissecting the individual. There appears to be a change in the slope of the length-weight relationship at about 600 mm TL. This may indicate that length at which this eel becomes mature. From 2 to 22 zones were counted on various otolith pairs. Though it is believed these represent age, it Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 207 remains to be determined if the observed zones are annual rings• Examination of the gonads of male and female G. mordax from Santa Catalina Island during a one-year period showed that gametogenesis was not completed. Water tem peratures in the northern parts of the range probably inhibit spawning. It is hypothesized that those eels in the southern part of the geographical range represent the breeding population. The north is repopulated by larvae carried northward with a near-shore current, the Cali fornia Countercurrent that develops in the fall and winter. The distribution of east Pacific Muraenidae and the characteristics of muraenid leptocephali are reviewed. The vertebral count for each species of east Pacific moray presently known is reported. A leptocephalus collected at Magdalena Bay, Baja California, is described as the larva mordax. The leptocephali of G. dovii and G. weineri are described, as well as another leptocephalus tentatively identified as that of G. tictus. Two Cther species of muraenid leptocephali are also described, though there are currently no known adults in the east Pacific. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LITERATURE CITED Al-Hussaini, A. H. 1947. The feeding habits and the morphology of the alimentary tract of some teleosts living in the neighborhood of the Marine Biological Station* Ghardaga, Red Sea. Mar. Biol. Sta. Ghardaqa (Red Sea)* Pub. 5»1-61. Bakus, G. J. 1964. The effects of fish grazing on in vertebrate evolution in shallow tropical waters. Occ. Pap. Allan Hancock Pdn. 27*1-29. ________. 1969. Energetics and feeding in shallow marine waters. Int. Rev. gen. exper. Zool. 4*275-369. Bardach, J. E. 1959. The summer standing crop of fish on a shallow Bermuda reef. Limnol. Oceanogr. 4(1)*77-85. ________* and L. A. Loewenthal. 1961. Touch receptors in fishes with special reference to the moray eel. Copeia (1)*42-46. ________* He Ee Winn* and D. W. Menzel. 1959. The role of the senses in the feeding of the nocturnal reef pred ators Gvmnothorax moringa and G. vicinus. Copeia (2)*133-139. Bertin, L. 1926. Les migrations de l'anus au cours de l'ontogenese chez les poissons apodes. Bull. Soc. zool. Fr. 51*327-344. Blache, J. 1963. Note preliminaire sur les larves lepto- cephales d'apodes du Golfe de Guinee (zone sud). Cah. O.R.S.T.O.M., s6r. Oceanogr., Pointe-Noire 3(5)*5-56. _______ _, 1967a. Contribution a la connaissance des Poissons Anguilliformes de la cote occidentale d'Afrique. Premiere note* Enchelycore nigricans (Bonnaterre, 1788). Bull. Inst. Pond. Afr, noire, Ser. A, 29(1)*164-177. ________. 1967b. Contribution a la connaissance des Poissons Anguilliformes de la cote occidentale d'Afrique. Deuxieme note* le genre Muraena (Artedi) Linne, 1758. Bull. Inst. Pond. Afr. noire, Ser. A, 29(1)*178-217. 208 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 209 ________• 1967c. Contribution a la connaissance des Poissons Anguilliformes de la cote occidentale d'Afrique. Troisieme note* le genre Echidna Forster, 1788. Bull. Inst. Fond. Afr. noire, Ser. A, 29(2)* 695-709. ________• 1967d. Contribution a la connaissance des Poissons Anguilliformes de la c6te occidentale d'Afrique. Quatrieme note* le genre Lycodontis McClelland, 1845. Bull. Inst. Fond. Afr. noire, Ser. A, 29(3)*1122-1187. ________• 1967e• Contribution a la connaissance des Poissons Anguilliformes de la cote occidentale d'Af rique. Cinquieme note* le genre Gymnothorax Bloch, 1795. Bull. Inst. Fond. Afr. noire, Ser. A, 29(4)* 1695-1705. ______• 1967£• Contribution k la connaissance des Poissons Anguilliformes de la cote occidentale d'Afrique. Sixikme note* les genres Anarchias. Uropterygius et Channomuraena (Muraenidae). Sull. Inst. Fond. Afr. noire, Ser. A, 29(4) *1706-1731. ________• 1971. Larves leptocephales des Poissons Anguilliformes dans le Golfo de Guinee (zone sud). Premiere note. Larves de Muraenidae. Cah. O.R.S.T.O. M., ser. Oceanogr. 9(2)*203-246. Blaxter, J. H. S. 1956. Herring rearing - II. The ef fect of temperature and other factors on development. Marine Res. 5*1-19. Bohlke, J. E., and C. C. G. Chaplin. 1968. Fishes of the Bahamas and adjacent tropical waters. Livingston Publ. Co., Wynnewood, Pa. 771 p. Briggs, J. C. 1961. The East Pacific Barrier and the distribution of marine shore fishes. Evolution 15(4)* 545=554. ________• 1964. Additional transpacific shore fishes. Copeia (4)*706-708. ________• 1967. Relationship of the tropical shelf regions. Stud. Trop. Oceanogr,, Miami 5*569-578. ________• 1970. Tropical shelf zoogeography. Proc. Calif. Acad. Sci., 4th Ser., 38(7)*131-138. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 210 Brock* V. 1954. A preliminary report on a method of esti mating reef fish populations. J. Wildl. Mgmt. 18(3)* 297-308. Brown, W. L. and E. D. Wilson, 1956. Character displace ment. System. Zool. 5(2)*49-64. Brunn, A. P. 1937* Contributions to the life histories of the deep sea eels* Synaphobranchidae. Dana Rep. 9* 1-31. Bussing, W. A. 1972. Recolonization of a population of supratidal fishes at Eniwetok Atoll, Marshall Islands. Atoll Res. Bull. 154*1-7. California Marine Resources Committee. 1953* Sardines and the ocean. Prog. Rep. Calif, coop, ocean, fish. Invest., 1 July 1952 to 30 June 1953*8-20. Carlisle, J. G«, J. W. Schott, and N. J. Abramson, i960. The barred surfperch (Amphistichus argenteus Agassiz) in Southern California. Calif, bept. Fish and Game. Pish Bull. 109*79 P. CaStle, P. H. J. 1963* The systematics, development and distribution of two eels of the genus Gnathophis (Cong- ridae) in Australasian waters. Zool. Publ. vict. Univ. Wellington 34*15-47. . 1965. Muraenid leptocephali in Australasian waters. Trans. R. Soc. N. Z.,Zool. 7(3)*57-84. . 1966. Les leptocephales jdans le Pacifique Sud-ouest. Cah. O.R.S.T.O.M., ser. Oceanogr. 4(4)* 51-71. ________• 1968. The world of eels. Tuatara 16(2)*85-97. ________• 1969. An index and bibliography of eel larvae. J. ir. B. Smith inst. Icht'nyoi. spec. pub. 7*121 p. Chave, E. H., and H. A. Randall, 1970. Feeding behavior of the moray eel, Gvmnothorax pictus. p. 173-178. In Fanning Island Expedition, Jan. 1970, Hawaii Inst. Geophys., Univ. Hawaii, HIG-70-23. D*Ancona, U. 1928a. Murenoidi (Apodes) del Mar Rosso e del Golfo di Aden. Material! raccolti dal Prof. Luigi Sanzo nella Campagna della R. N. "Ammiraglis Magnaghii" 1923-24. Memorie R. Com. talassogr. ital. 146*1-146. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 211 ________• 1928b, Notizie preliminaire sugli stadi larvali di Murtriiolui raccolti dal Prof, Luigi Sanzo nel Mar Rosso e nel Golfo di Aden durante la crociera della R. N. "Ammiraglio Magnaghii" 1923-2**. Atti Acad, nsz, Lincei Rc,, 6 ser,, 7(5)i**27-**31» , 1928c, Sulla possibilita di ordinaire sistem- aticamente le specie larvali dei Murenoidi, Atti Accad. naz, Lincei Rc., 6 ser., 7(6)*516-520• ________• 1930. In Joubin. 1928-38. Fauna ichthyologi- que de l'Atlantlque Nord. Horst and fils, Copenhagen. 23 P. ________. 1931• Uova, larva e stadi giovanili di Tele- ostei Apodes, Fauna flora Golfo Napoli 38*9* 1 -156. . 1932. Per la miglior conoscenza della sistem- atica degli "Apodes (Muraenoidi)". Archo. Zool. Ital. 16*12^9-1253. Darnell, R. M. 1968. Animal nutrition in relation to secondary production. Amer. Zoologist 8*83-93. Davis, R. E. 196**. Daily "predawn" peak of locomotion in fish. Anim. Behav. 12*272-283. ________, and J. E. Bardach. 1965. Time-co-ordinated pre feeding activity in fish. Anim. Behav. 13*15* 1 -162. Della Croce, N., and P. H. J. Castle, 1966. Leptocephali from the Mozambique Channel. Boll. Musei. 1st. Biol, Univ. Genova 3**(211) *149-164, Ekman, S. 1953. Zoogeography of the sea. Sidgwick and Jackson, London. *H7 p. Eldred, B. 1966. The early development of the spotted worm eel, Mvrophis punctatus Lutken (Ophichthidae). Fla. Bd. Conserv. Mar. Res. Lab., Leaf. Ser. **(!)* 1-13. . 1988a. Larvae of the marbled moray eel, Urop- terygius .iuliae (Tommasi, i960). Fla. Bd. Conserv. Mar. Res. Lab., Leaf. Ser. **(8)*1-4, ________. 1968b. The larval development and taxonomy of the pygmy moray eel, Anarchias voshiae Kanazawa 1952. Fla. Bd. Conserv. Mar. Res. Lab., Leaf. Ser. **(10) * 1-8. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 212 ________• 1969a. The larva of the redface moray, Rabula acuta (Parr, 1930) Bohlke and Chaplin, 1968, Fla. Dept. Nat. Resources Mar. Res. Lab., Leaf. Ser, 4(11): 1-5. ________• 1969b. Embryology and larval development of the blackedge moray, Gymnothorax nigromarginatus (Girard, 1859). Fla. Dept. Nat. Resources Mar. Res. Lab., Leaf. Ser. 4(13)il-l6. ________• 1970a. Larva of the purplemouth moray, Gym no thorax vicinus (Castlenau, 1855). Fla. Dept. Nat. Resources Mar. Res. Lab., Leaf. Ser. 4(l4)il-8. _______. 1970b. Larva of the spotted moray, Gvmnothorax morlnga (Cuvier, 1829). Fla, Dept. Nat. Resources Mar. Res. Lab., Leaf. Ser. 4(15)il-10. ________. 1970c. Larva of the green moray, Gvmnothorax funebris Ranzani, 1840. Fla, Dept. Nat. Resources Mar. Res. Lab., Leaf. Ser. 4(l6):l-4, Emerson, W. K. 1967. Indo-Pacific faunal elements in the tropical eastern Pacific, with special reference to the mollusks. Venus 25(3)*85-93. Emery, K. 0. i960. The sea off Southern California. John Wiley and Sons, Inc., New York. 366 p. Fish, M. P. 1927. Contributions to the embryology of the American eel (Anguilla rostrata Lesueur). Zoologica, N.Y. 8(5)*289-3247 Fitch, J. E., and R. J. Lavenberg. 1971. Marine food and game fishes of California. Univ. of Calif. Press. Berkeley. 179 p. Ford, E. 1931. Changes in length during the larval life and metamorphosis of the freshwater eel (Anguilla vulgaris Turt.). J. mar. bid. Assoc. U.kT 17* 987-1600. Fowler, H. W. 1938. The fishes of the George Vanderbilt South Pacific Expedition, 1937. Monogr. Acad. Nat. Sci. Philad, 2*349 p. ________• 1944. Results of the fifth George Vanderbilt Expedition (1941). Monogr. Acad. Nat. Sci. Philad. 6*349 p. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 213 ________• 1956. Fishes of the Red Sea and southern Arabia. Vol. I. Branchiostomida to Polynemida. Weizmann Science Press, Jerusalem. 240 p. Ganapati, P. N«, and N; S. Raju. I960. On the eggs and early development of eels off Waltair coast. J. zool. Soc. India 12(2)*229-238. Gosline, W. A., and V. E. Brock, i960. Handbook of Hawaiian fishes. Univ. of Hawaii Press, Honolulu. 372 p. Grassi, G. B. 1896. The reproduction and metamorphosis of the common eel (Anguilla vulgaris). J microsc. Sci.. n.s. 39(3)*371-3551 ________> » 1897. The reproduction and metamorphosis of the common eel (Anguilla vulgaris). Proc. R. Soc. London 60*260-271. ___________1910. Contribuzione alio studio dello sviluppo dei murenoidi. I. Muraena helena. II. Di alcune uova e prelarva, che si potrebbero suppore appartenenti all! Anguilla anguilla. Memorie R. Com. talassogr. ital. 1:1-16. . 1915. Contributo alia conoscenza della uova e delli larvae dei murenoidi (Aggiunta II alia mia mono- grafia sulle metamorfosi dei murenoidi). Atti Accad. naz. Lincei Memorie, 5 ser., 10(16)1693-711. Halstead, B. W. 1959. Dangerous marine animals. Cornell Maritime Press, Cambridge. 146 p. Hiatt, R. W., and D. W. Strasburg. i960. Ecological rela tionships of the fish fauna on coral reefs of the Mar shall Islands. Ecol. Monogr. 30*65-127. Hildebrand, S. F. 1946. A descriptive catalogue of the shore fishes of Peru. Bull, U.S. natr. Mus. 189*530 p. Hoar, W. S., and D. J. Randall (ed.). 1969. Reproduction and growth, bioluminescence, pigments and poisons. Jta Fish physiology, vol. III. Academic Press, New York. 485 p. Hobson, E. S. 1959. Some ecological observations of Muraenidae occurring in various rocky, shallow water areas about Oahu. Unpublished data. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 214 ________• 1968. Predatory behavior of some shore fishes in the Gulf of California. U.S. Dept. Interior, Bur= Sport Fish, and Wildlife, Res. Report 73*92 p. Hoglund, R, 1964. An inquiry into the temperraent of the moray eel. Underwater Natur. 2(2)*15. Hubbs, C. L., and R. H. Rosenblatt. 1961. Effects of the equatorial currents of the Pacific on the distribution of fishes and other marine animals. Tenth Pac. Sci. Cong., Abst. of Symposium Papers* 340-341. Hutchins, L. W. 1947. The bases for temperature zonation in geographical distribution. Ecol. Monogr. 17(3)* 325-335. Jensen, A. C. 1965. A standard terminology and notation for otolith readers. Intemat. Comm, Northwest Atlan tic Fish., Res. Bull. 2*36-38. Jones, J. H. 1971. General circulation and water charac teristics in the Southern California Bight, So. Calif. Coastal Water Res. Project, Los Angeles. 37 p. Klopfer, P. H. 1962. Behavioral aspects of ecology. Prentice-Hall, Englewood Cliffs, N. J. 171 p. Lea, E. 1913* Muraenoid larvae from the "Michael Sars" North Atlantic Deep-Sea Expedition, 1910. Rep. Sars N. Atlantic Deep Sea Exped. 3(2)*1-48. McCleneghan, K. 1968. Feeding behavior of three species of wrasse (family L&bridae) from Southern California. Unpublished data. MacGinitie, G. E., and N. MacGinitie. 1949. Natural history of marine animals. McGraw-Hill, New York. 473 P. Marshall, N.B. 1965. The life of fishes. Weidenfeid and Nicolscn, London. 402 p. Morris, R. A. 1959. Food habits of certain representa tives of the family Muraenidae. Unpublished data. Nair, R. V., and K. H. Mohamed. i960. Studies of the leptocephali of Bombay waters. V. A few other lepto- cephali. Proc. Indian Acad. Sci., Ser. B, 52(5)* 209-219. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 215 National Academy of Sciences - National Research Council, Washington D.C., Division of Biology and Agriculture, 1970. Committee on ecological research for the inter- oceanic canal, Atlantic-Pacific interoceanic canal study commission. Interoceanic Canal Studies 1970. U.S. Govt. Printing Office. Appendix 16, 98 p. Nikolsky, G. V. 1963. The ecology of fishes. Academic Press, New York. 352 p. O'Connell, C. P. 1953* The life history of the cabezon, Scoroaenichvthys marmoratus (Ayres). Calif. Dept. Pish and Game, Fish Bull. 93*76 p. Odum, E. P. 1969. The strategy of ecosystem development. Science 164*262-269. Pantulu, V. R., and S. Jones. 1954. On some metamorphos ing stages of eels (Muraenidae) from the estuary of the Burhabulong River, Orissa State. Proc. Indian Acad. Sci., Ser. B, 39(1)*24-35. Perlmutter, A. 1954. Age determination of fish. Trans. N. Y. Acad. Sci., Ser. II, 16(6)*305-311. Phillips, J. B. 1964. Life history studies on ten species of rockfish (genus Sebastodes). Calif. Dep«. Fish and Game, Fish Bull. 1261 70 p. Pillay,.T. V. R. 1952. A critique of the methods of study of food of fishes* J. zool. Soc. India 4(2)*185- 200. Quast, J. C. 1968. Estimates of the populations and the standing crop of fishes. Calif. Dept. Fish and Game, Fish Bull. 139*57-79. Randall, J. E. 1963. An analysis of the fish populations of artificial and natural reefs in the Virgin Islands. Carib. J. Sci. 3(l)»31-**7. _. 1967. Food habits of reef fishes of the West Indies. Stud. Trop, Oceanog., Miami 5*665-84?. _• 1969. How dangerous is the moray eel? Austral. Nat. Hist. 16(6)*177-182. Raymont, J. E. G. 1966. The production of marine plank ton. Advan. Ecol, Res. 3*117-205. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 216 Reid, J. L., Jr., G. Roden, and J, wyllie. 1958. Studies of the California current system. Prog. Rep. Calif, coop, ocean. Pish. Invest., 1 July 1956 to 1 Jan. 1958i27-57. Rosenblatt, R. H., and B. W. Walker. 1963. The marine shore fishes of the Galapagos Islands. Occ. Pap. Calif. Acad. Sci. 44*97-106. . J. E. McCosker, and I. Rubinoff. 1972. Indo- West Pacific fishes from the Gulf of Chiriqui, Panama. Contrib, Sci. 234*1-18. Rounsefell, G. A., and W. H. Everhart. 1953. Fishery science, its methods and applications. John Wiley and Sons, Inc., New York. 444 p. Schmidt, E. J. 1906. Contributions to the life history of the eel (Anguilla vulgaris Flem.). Rapp. P,-v. Reun. Cons. perm. int. Explor. Mer 5(4) *137-264, 267-273. _. 1912. Danish researches in the Atlantic and Mediterranean on the life-history of the freshwater eel (Anguilla vulgaris Turt.) with notes on other species. Int. Revue ges. Hydrobiol. Hydrogr. 5*317-342. ________• 1913. On the identification of muraenoid larvae in their early ("preleptocdphaline") stages. Meddr. Komm. Havunders., Ser. Piskeri 4(2)*1-13. Schott, J. W. 1965. A visual aid for age determination of immersed otoliths. Calif, Pish Game 51(1)*56. Smith, W. W. 1968. Otolith age reading by means of sur face structure examination. J. cons. perm. Int. Explor. Mer 32(2)*270-277. Southwood, T. R. E. 1968. Ecological methods. Methuen and Co. Ltd., London, 391 p. Spoor, W. A. 1941. A method for measuring activity of fishes. Ecology 22(3)i329-331. Starck, W. A., II, and W. P. Davis. 1966. Night habits of fishes of Alligator Reef, Florida. Ichthyologica 38(4)*313-356. Stevenson, R. E. i960. Winds over coastal southern Cali fornia. Bull. So. Calif. Acad. Sci. 59(2) *103-119. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 217 Suyehiro, Y. 1942. A study on the digestive system and feeding habits of fish. Jap. J. Zool. 10(1)*1-303. Sverdrup, H. U., and R. H. Fleming. 1941. The waters off the coast of Southern California, March to July, 1937. Bull. Scripps Inst. Oceanogr. tech. Ser. 4i261-378. . M. W. Johnson, and R. H. Fleming, 1942, The oceans, their physics, chemistry and general biology. Prentice-Hall, Inc., New York. 1087 p. Takai, T., and T. Tsutsumi. 1959* Daily periodic move ments of the four species of apodal fishes, particular ly in their creeping feeding habits. J. Schimonoseki Coll. Fish, 81191-197, Walker, B. W. 1952. A guide to the grunion. Calif. Fish Game 38(3)*409-420. 1961. The marine fishes of the Galapagos Islands. Tenth Pac. Sci. Cong., Abst. of Symposium Papers* 470-471, Winn, H. E., and J. E. Bardach. 1959. Differential food selection by moray eels and a possible role of the mucous envelope of parrot fishes in reduction of predation. Ecology 40(2)*296-298. Woolf, C, M. 1968. Principles of biometry. Van Nostrand Co., Inc., New Jersey. 359 p. Wooster, W. S., and J. L. Reid, Jr. 1963. Eastern bound ary currents, p. 253-280. In M. N. Hill (ed.) The sea. vol. 2. Interscience Publ., New York. Wyllie, J. G. 1966. Geostrophic flow of the California Current at the surface and at 200 meters. Calif. Mar. Res. Comm., Calif. Coop, oceanic Fish. Invest,, Atlas No. 4, 288 p. Young, P. H. 1963. The kelp bass (Paralabrax clathratus) and its fishery, 1947-1958. Calif. Dept. Fish Game, Fish Bull. 122*67 p. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. INFORMATION TO USERS This material was produced from a microfilm copy of the original document. While the most advanced technological means to photograph and reproduce this document have been used, the quality is heavily dependent upon the quality of the original submitted. The following explanation of techniques is provided to help you understand markings or patterns which may appear on this reproduction. 1.The sign or "target" for pages apparently lacking from the document photographed is "Missing Page(s)". 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Core Title The ecology and behavior of the California moray eel Gymnothorax mordax (Ayres, 1859) with descriptions of its larva and the leptocephali of some other east Pacific muraenidae

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