, SKATES, RAYS, AND CHIMAERAS

UNITED STATES iViarine Biological Laboratory DEPARTMENT OF THE THE INTERIOR N0V2 8 1961 FISH AND WILDLIFE SERVICE WOODS HOLE, MASS. BUREAU OF COMMERCIAL FISHERIES

CIRCULAR 119 TABLE 1. —Maximum sizes of common of sharks

Species SHARKS, SKATES, RAYS, AND CHIMAERAS

By

J. R. Thompson and Stewart Springer

FISH AND WILDLIFE C'RCULAR 119

BUREAU OF COMMERCIAL FISHERIES, Donald L. McKernan, Director

FISH AND WILDLIFE SERVICE, Clarence L. Pautzke, Comm,ss/oner

UNITED STATES DEPARTMENT OF THE INTERIOR, Stewart L Udall, Secretary

UNITED STATES GOVERNMENT PRINTING OFFICE* WASHINGTON • 1961

CONTENTS Page

Introduction 1 Class , the cartilaginous fishes 2 Sharks 4 Skate s and rays 10 Chimaeras 14 Annotated list of references 16

ILLUSTRATIONS

"Family tree" of the vertebrates illustrating, in the opinion of many zo- ologists, the relations existing among members of the group 2 A from the and her litter. Few sharks produce this many young at one time 4 A "typical" , illustrating terms used in description 5 Top: A small spiny dogfish shark, Squalus CubenSlS, from the Gulf of Mexico. Many species of sharks are many times smaller than this species. Bottom: A large silky shark, Eulamia floridana, taken on a tuna longline. These large, oceanic sharks sometinries reach lengths of ab out lOfeet 6 A small thresher shark, AlopiaS vulpinus. A 14-foot specimen of this species, recently taken was estimated to weigh approximately 500 pounds and possessed a caudal lobe measuring 7^ feet. The long caudal lobe is apparently used to stun prey 9 Removing the liver from a large silky shark 10 A generalized skate illustrating terms used in description 11 A "typical" ray, the roughtail stingray, Dasyatis centroura. This specimen measured 62 inches across the fins and weighed 285 pounds. Such rays are taken frequently in trawl drags along the east coast of the United State s 13 A generalized chimaera illustrating terms used in description 14 ABSTRACT

A general introduction to the class Chondrichthyes is presented.

Material included encompasses, in broad terms, characteristics of the class and of its components. General statements on reproduction, numbers and general distribution, size, food and feeding, sensory- perception, structural adaptations to specific modes of life, and relation to man are included. A short, annotated list of references directs the reader to more specific and detailed sources for further study.

IV s

SHARKS, RAYS, SKATES, AND CHIMAERAS By

J. R. Thompson and Stewart Springer Fishery Methods and Equipnnent Specialists Bureau of Commercial Fisheries

INTRODUCTION

Sharks, skates, rays, and, to a techniques. They are difficult to keep in lesser extent, chimaeras--all grouped captivity, and their collection and study by zoologists in the single vertebrate as living is quite expensive. class Chondrichthyes (cartilaginous But over the years, zoologists have fishes)--have been the subjects of in- succeeded in amassing sufficient data terest for many years. On the negative to outline, in greater or lesser detail, side, the interest in many of these the characteristics and habits of many fishes has arisen largely from fear-- of the cartilaginous fishes. fear of injury to fishermen and swimmers, fear of damage to fishing This paper has been written as an gear and equipment, and the fear that introduction to the members of the class is a natural accompaniment of a lack of Chondrichthyes. The information con- knowledge. On the positive side, the tained has been dra'wn from the litera- interest has arisen as a result of at- ture, from zoologists and fishermen of tempts to turn some of these fishes many countries, and from the personal to economic advantage, and out of man' experiences and observations of the innate curiosity concerning the world authors. The purpose of the paper is to around him. answer the many general questions asked fishery zoologists each year Despite widespread interest, ac- concerning sharks, skates, rays, and cumulation of adequate knowledge con- chimaeras, or if not to ansv/er, at cerning sharks and their close relatives least to suggest further, more detailed has been slow, and a large body of sources of information. Toward this speculation and "old wives' tales" has end, the text has been kept brief and arisen as a result of attempts to fill general, and an annotated list of ref- in the gaps. Obstacles to the study of erences has been included. In most cartilaginous fishes are many. Most cases, the reader who is sufficiently of these fishes are pelagic, and many interested to pursue the subject beyond of them inhabit the open waters of the the confines of this circular will find high seas where large ocean-going more material in the references listed. vessels are needed for their study. He may also find clues to further re- Many species are confined to relatively search sources in the bibliographies great depths where collection is dif- contained in the references examined. ficult and expensive. Even those species To facilitate use, the references are that inhabit shallower, coastal water listed by topic in an arrangement require special collecting and handling roughly paralleling the arrangement of the subheadings of the text.

Note.—J. R. Tlioiiipson. U.S. Fish and Wildlife Service, Pasca>Joula, Misi.; -ind Stewart Springer. U. S. Fish and Terms commonly applied to car- Wildlife Service. Washington, D. C. tilaginous fishes and other large marine creatures are frequently subject to the Greek words elasmo, nn e a n i n g confusion. Scientific names of Greek platelike or si it like, and branchia, or Latin derivation are frequently re- meaning gill) which has come into duced to English form and used as common usage and which refers to any English common names. Chimaera is shark, skate, or ray, but not to chi- such a name (derived from the Greek maeras. The anglicized ^ord selachian chunair, meaning goat), and it is useful (from the Greek term coined to desig- because it covers all one closely re- nate fishes having cartilaginous skele- lated group of cartilaginous fishes in- tons instead of bone) has become even cluding some known as ratfishes, some more restrictive and now refers as elephant fishes, and others. Elasmo- only to sharks, not to skates or branch is another word (derived from rays.

CLASS CHONDRICHTHYES, THE CARTILAGINOUS FISHES

Members of the class Ghon- which are composed of cartilage rather drichthyes, the sharks, skates, rays, than true bone, a feature which sets and chimaeras, possess well-developed them apart from the bony fishes and lower jaws which set them apart from other higher vertebrates. The car- the lampreys, hagfish, and other lower tilaginous skeletons, how^ever, are often vertebrates; and they possess skeletons made up of structural components that

AVES (Birds) MAMMALIA

REPTILIA

AMPHIBIA

CHONDRICHlVfE's (Cartilaginous fishes) (Higher bony fishes)

PLACODERMI (Archaic jawed fishes)

AGNATHA (Jawless fishes)

} NON-VERTEBRATE CHORDAnS

'Family tree" of the vertebrates illustrating, m theopinionof many zoologists, the relations existing among members nf the group. are so stiffened with mineral deposits Skates and rays have a more-or- that microscopic examination and a less flattened appearance, and all ex- knowledge of the developmental cept a few are either wholly or partially processes involved in cartilage and covered with denticles or spines, which bone formation are necessary todeter- may be scattered irregularly or ar- mine that cartilage, not bone, makes ranged in definite patterns. All skates up the skeletons. For this reason, we and rays have five gill slits on each often speak of the "backbone" of a shark side of the lower surface of the head- when referring to the hard, cartilagi- neck region. nous (but bonelike) vertebrae that com- prise the structure that places the Chimaeras, like sharks, are fusi- members of the class Chondrichthyes form in shape. Unlike sharks, they in the Vertebrata. are usually smooth skinned, although a few denticles appear on the young Fossil records of primitive fishes and may persist in some adults, and ancestral to present-day sharks, they have only one external gill open- skates, rays, and chimaeras, date back, ing on each side. perhaps a quarter of a billion years, to the Devonian period (mid-Paleozoic Although some sharks and rays era). Moreover, representatives of all enter fresh water for short periods, of the presently existing families of and a few custonnarily enter fresh water cartilaginous fishes have been found in to give birth to their young, most the fossil deposits of the early Ter- species are exclusively marine. One tiary period (early Cenozoic era)-- species of shark is said to be es- good evidence that these fish families tablished as a permanent resident of have been on earth at least a thousand Lake Nicaragua, but this is exceptional. times longer than the human family. Most chimaeras inhabit deep water, This long geological history also indi- and all live in strictly oceanic environ- cates that the cartilaginous fishes can ments. maintain themselves successfully in spite of changing environment and vary- Reproductive processes are ex- ing conditions of competition, and that tremely variable in the class Chon- they have been remarkably stable (in drichthyes. Many members of this the biological sense of resistance to class are ovoviviparous and bring forth evolutionary change) since at least the living young that have been hatched Tertiary period. from eggs inside the oviducts of the mother. Once hatched, the embryos Zoological definitions adequate to are nourished in a variety of ways. off vertebrates from set the classes of Some members are viviparous, or one another with precision, or to define nearly so, and bring forth living young the subdivisions of cartilaginous fishes, that have been nourished by substances are necessarily long. To find the de- in the mother's blood stream trans- tailed and exact definitions required for ferred to the developing embryo through taxonomic work, the reader is referred a placenta. Some are oviparous and lay to one or more of the appropriate cita- eggs encased in horny or leathery cap- tions at the end of this circular. For sules, which are deposted on the ocean general purposes, the following re- floor. Regardless of the developmental marks should be sufficient to separate process, the number of eggs produced the major groups: by a single cartilaginous fish is very Sharks usually have the shape of a small compared with the number of eggs "typical fish"--a fusiform shape--and produced by a single bony fish. But the most of them are densely covered -with cartilaginous fishes are able to main- small, toothlike scales called denticles tain their numerical status quo, because which give the skin its rough sand- their young, at birth or hatching, are paperlike feeling. In addition, all sharks much larger than the newly hatched have from five to seven gill slits or young of most kinds of bony fishes and external gill openings on each side of are, therefore, better able to defend the head or neck. themselves against predators. A A great hammerhead from the Gulf of Mexico and her litter. Few sharks produce this many young at one time. greater proportion of young cartilagi- much greater when fertilization is in- nous fishes reach maturity for that ternal than w^hen it is external as with reason. most bony fishes. Male chondrichthoid fishes are easily recognized by the Fertilization is internal throughout presence of a pair of intromittent the class. Internal fertilization is organs called claspers that arise from another mechanism by which the car- the inner margins or bases of the tilaginous fishes make up for the small pelvic fins and usually extend beyond number of eggs produced. The chances the tips of the fins in mature cartilagi- of the eggs becoming fertilized are nous fishes.

SHARKS

Numbers and General water realms which have not been Distribution thoroughly investigated. An estimated 300 species of sharks are recognized in the world today. In A few species, including the Green- several instances, especially among land shark and the Pacific sleeper the larger, far-ranging species, we shark, inhabit very cold seas, but the have probably described the same variety and number of sharks are sharks under more than one name. greater in tropical and subtropical There are, however, undoubtedly other waters. Sharks are present in greater species existing that have not been given variety, and probably also in greater names as yet, particularly in the deeper abundance, in moderate depths- -from sections of the ocean and in the mid- 50 to more than 500 fathoms. Sonne Dorsal Fin

Pectoral Fins

Gill slits

Nostril

Upper lobe. Caudal Fin

Lower lobe. Caudal Fin

A"typical" shark, illustrating terms used in description

sharks are found in much greater Size depths, although actual captures have not been made as yet in waters deeper A table on the inside cover of this than 1,500 fathoms (9,000 feet). There circular lists the maximum recorded are also several species that inhabit lengths and weights of many of the very shallow waters along the coasts. common species of sharks. Sharks These include some of the dogfishes, range in size from individuals that small blacktip sharks, hammerheads, mature at a total length of less than 1 nurse sharks, sand sharks, and sand- to individuals that do not mature bar sharks. foot until they are many feet long and that Abundance may reach lengths of about 45 feet. One of the smallest sharks known, Despite their appearance, at times, Squaliolus sp., lives only indeep water in great concentrations, sharks are and apparently never reaches a length not normally abundant in comparison much in excess of 6 inches. The little with many bony fishes. In the United green dog shark, EtmopteruS ViretlS, States the spiny dogfish, one of the from the Gulf of Mexico, is full-grown smaller sharks, is connmon off the at a length of about 9 inches, and newly coasts of New England and the Middle born individuals are about 4 inches Atlantic States in the long. and off the coasts of Washington and Oregon in the Pacific Ocean. In these areas it is, at times, common enough The largest species, by weight, is to be a great nuisance to commercial the whale shark. Another large species, and sport fishermen. The larger sharks the basking shark, is somewhat less are less abundant. bulky, but about as long. Top: A small spiny dogfish shark, Squalus cubensis, from the Gulf of Mexico. Many species of sharks are many times smaller than this species. Bottom: A large silky shark, Eulamia floridana, taken on a tuna longline. These large, oceanic sharks sometimes reach lengths of about 10 feet. Most, or all, of the maximum exploratory research vessel Oregon recorded sizes contained in the table have confirmed this behavior. Whale refer to female sharks, and, indeed, sharks have also been observed to the females of all shark species studied drive tuna fishermen out of their fishing for this attribute average somewhat racks. But on the basis of accumulated longer with the average weight ap- evidence, the whale shark is probably preciably greater than that of males. not ordinarily aggressive toward large On the Atlantic coast of the United creatures including man. It probably States, for example, adult male sand- swallows large objects only if they are bar sharks vary from 5 feet 10 inches taken incidental to its regular feeding in length to 7 feet 4 inches, whereas activities. This, however, is sufficient female adults vary from 6 feet to 7 reason for treating these huge and feet 8 inches. This represents an powerful sharks with caution. average 5 percent longer length for the females, and this longer length is ac- A few sharks, including the white companied by an average 25 percent shark and the tiger shark, nornaally greater weight. attack large and active prey. Other sharks, including the snnaller hammer- Food and Feeding Habits heads, and small blacktip sharks seem to prefer and small fishes. All sharks are primarily predators The tiger shark, which would normally in the sense that they all feed on be expected to obtain its food by active life. The variety of animal life con- pursuit and capture of other fishes, sumed, however, is almost limitless, sometimes haunts steamer lanes to and nearly all sharks excepting perhaps gather in garbage. A large tiger shark, such forms as the specialized basking captured by the crew of the Oregon, sharks, are secondarily scavengers. contained not only food that had been Some sharks appear to be indiscrimi- thrown overboard several hours ear- nant in their feeding habits. Curiously, lier, but also tin cans and milk cartons. the largest kno^vn species feed on the Coastal fishermen frequently complain smallest prey, and some of the smallest about sharks of several species which sharks consume relatively large crea- follow their vessels and tear up the nets tures. to obtain the fish contained within.

The huge whale sharks and basking Large sharks such as the ^vhite sharks are primarily filter feeders. shark, the dusty shark, and the white- These sharks s^vim with their mouths tip eat porpoises' when they can cap- open and strain or filter out small ture them. Porpoises are much faster planktonic organisms as the water, than sharks and can outrun them or coming in through the mouth, passes drive them away. If, however, a por- over sievelike gill rakers and out poise is weakened through fatigue or through the gill slits. Examination of severe injury and is isolated, it may stomach contents reveals that these meet a sudden end in an attack by large sharks filter great quantities of sharks. Observations, made from the small Crustacea and minute fishes in Bureau's research vessel Oregon, have this manner, and such small prey con- substantiated tales of porpoises ac- stitutes the primary source of food for tively driving sharks a'way from their them. On the other hand, there is little young and of schools of porpoises, the doubt that the whale sharks also, oc- members of which would take turns casionally, consume larger prey. driving off attacking sharks and rest- Fishermen have reported that whale ing. At other times, however, porpoises sharks, feeding at the surface on great and sharks may even feed together on schools of small fishes, occasionally trash fish throw^n from a boat, and the trap tunas which are also feeding on porpoises apparently have sufficient the small fishes and which, in their 'porpoises are marine mammals. quest for food, follow the small fishes The term "dolphin" is sometimes used for these animals, but "porpoise" is straight into the whale shark's mouth. probably preferable because "dolphin" is used also tode- Observations from the Bureau's note a bony fish commonly taken by sport fishermen. confidence in their own speed and nervous system of the shark is de- strength that they do not waste energy- centralized to a much greater extent attacking the sharks when the sharks than it is in the higher vertebrates, are not aggressive. and the areas of the brain usually re- garded as thought centers are absent in sharks. Sharks have been shown ex- Some of the smaller species, in- perimentally to be capable of develop- cluding the deep-water green dog shark, ing rather complicated responses to are thought by some to hunt in packs, conditioning stimuli and may thus because their stomachs often contain be able to learn at the reflex the beaJ^s of and octopus, repre- level. senting prey too large and agile for these small sharks to kill and eat alone. Anatomical Features

Sensory Perception In addition to the general anatomi- cal features described in the introduc- Studies on sensory perception of tion, each species of shark has its own sharks have been difficult to carry structural adaptations. Many of these out satisfactorily. In the broadest con- features can be correlated with a more notation, the senses of sharks are or less specific way of life assumed by similar to those of other animals. The the shark species. A few examples of sense of smell is presumed tobe highly divergence from the generalized developed and has been shown experi- shark pattern and of adaptive fea- mentally to play a major role in food tures can be given here, many more finding. Sharks also have a sense exist. corresponding to our sense of taste, but organs for tasting are widely The angel sharks, found on both scattered over the skin of the head and coasts of the United States, diverge even other parts of the body. Although from the typical fusiform shape and this sense is in some way related to display a flattened appearance char- feeding habits, it is possible that in acteristic of rays. A second raylike sharks it serves other functions as well. shark, although not flattened, is the Sharks' eyesight is apparently adapted sawshark of the deep waters of the best for the detection of movement, but Straits of which resennbles their eyes are extremely complicated closely the sawfish of shallow coastal structures, adapting especially to low waters. Sawfish, though sharklike, are light levels. true rays. In spite of the superficial resemblance to rays exhibited by Some sharks have calcareous these two shark species, close ex- bodies in the chamber of the inner ear amination shows that their more which are presumed to be associated basic characteristics are those of with the sense of balance. Sharks are sharks. responsive to noises and pressure but the importance of sound w^aves, The thresher shark has a pecul- pressure differentials to sharks is and iarly enlarged and elongated upper not well understood. Experimental pro- caudal lobe which, according to fisher- cedures to determine the roles of the men observers, it uses to stun its prey ears (internal) and the lateral line by "threshing" around in a school of organs have met with only limited fish. Its tail is one of the toughest success. flexible structures developed in the animal kingdom. Many other correla- Sharks apparently have a very low tions between anatomy and mode of life intelligence level and many, if not all, can be pointed out. Fast- swimming, of their activities are reflexive. The oceanic sharks, such as the mako and A small thresher shark, Alopias vulpinus. A 14-foot specimen of this species, recently taken was estimated to weigli approximately 500 pounds and possessed a caudal lobe measuring 7j feet. The long caudal lobe is apparently used to stun prey. the white sharks, are streamlined and Relation to Man possess large stiff pectoral fins for The relation of sharks to man stabilizers. contrast, rather In most stems from commercial utilization of sluggish sharks, such as the cow sharks and shark products by man and sharks, nurse sharks, and even the from damage caused man by sharks. bull sharks, are less streamlined and often more bulky, or display adapta- Until 1950, a commercial fishery tions to other ways of life. The large for sharks was carried on in the United whale sharks, which engulf and strain States, on both coasts, and the annual their prey in great volumes of water, catch reached a maximum of 4.5 mil- have terminally placed mouths to better lion pounds landed on the Atlantic coast facilitate their feeding. The basking and 39 million pounds on the Pacific sharks have extremely ^vide mouths coast. The fishery was carried out nearly terminal in position to better chiefly to obtain the shark-liver oil engulf and strain great quantities of which is rich in vitamin A. Byproducts water. Most other sharks have their of the oil industry included: hides, mouths placed far ventrally. used for high-quality leather products; fins (of some species), sold as spe- Several deep-sea species, includ- cialty food items; meat, salted or sold ing probably the little green dog shark fresh as food for human consumption in that lives at depths exceeding 1,000 some areas; carcasses, ground into feet, possess the ability to produce meal; and teeth and vertebrae, cleaned light in their otherwise totally dark and sold to curio shops. With the advent environment. of cheaper sources of vitamin A, shortly prior to 1950, most of the commercial shark fishing operations in this coun- try were suspended. Sharks interfere with operations in many instances. In the Gulf of Mexico, sharks occa- sionally cause severe economic losses through their habit of biting and tearing the trawl nets to get at the catch. An estimated 20 percent loss in salable fish due to shark damage has been cited for the tuna longline fisheries of the world. Also, in many localities, the seasonal abundance and the local concentration of some species of sharks force cessation of gill-net operations and otherwise influence the choice of gear and the location of fishing grounds.

In 1958 the American Institute of Biological Sciences (AIBS) inaugurated a Shark Research Panel for the pur- pose of studying all aspects of the biology of elasmobranch fishes. One of the functions is to compile a shark- attack file. Records accumulated through this effort show that, in 1959, there were 39 shark attacks on man Removing the liver from a large silky shark. involving at least 18 fatalities.

SKATES AND RAYS

Numbers and General Distribution taceans that characterize the tidal zone. Below 1,500 fathoms, our knowl- Included in the same group with the edge of the bottom fauna is scanty, but, skates and rays are the sawfishes, if skates and rays are present, they guitarfishes, electric rays, stingrays, undoubtedly are very scarce. eagle rays, and mantas. All told, prob- ably about 400 species of the group are The eagle rays, mantas, and a few known. others are capable of tremendous leaps from the water, and authentic reports The group as a whole is widely are available of these large fishes distributed. Like the sharks, more towing moderate-size vessels for rela- species, and probably more individuals, tively great distances at high speeds. are found in tropic and subtropic seas Other skates and rays probably rely on than in colder ^^aters; but there are short bursts of speed followed by several species that do frequent the periods of drifting or lying quietly on cold-water regions of the world, in- the bottom rather than on sustained cluding some skates that live in water high speed or s\vimming po^ver. Even as cold as 29° F. Skates, rays, and the mantas, usually seen only on the their close relatives may be found from surface of the water, probably spend the shoreline to a depth of about 1,500 some of their time resting quietly on fathoms. At least one species occa- the bottom. Stingrays (Dasyatis) are sionally splashes along the very edge bottom dwellers and are sometimes of the sea, on the tide line of the found partly buried in the sand with beaches, in search of the small crus- only the eyes and the area surrounding

10 DORSAL VENTRAL

Nostril

Caudal Fin

Dorsal Fin

'M^ Dorsal Fin

A generalized skate illustrating terms used in description. the spiracles visible. But there are Abundance exceptions- -one species, at least, In numbers of individuals, the is pelagic. The pelagic stingray, skates and rays compare more favor- Dasyatis violacea, has been taken by ably with the sharks than with the bony Bureau research vessels in both the fishes. They are abundant locally and Atlantic and Pacific near the surface seasonally, but cannot be considered hundreds of miles from land. abundant inhabitants of the seas in general. Stingrays are often sufficiently Although basically marine fishes, numerous along the coasts of South and a few species of stingrays have taken Central America, in the Caribbean, and up residence in the lower parts on the coastal grounds of the of some rivers in Florida and South southern portion of the United States to America, and sawfishes f r e qu e n 1 1 y constitute a serious nuisance to com- enter fresh water--often for prolonged mercial fishing operations. They are periods. also found around some bathing beaches,

11 where they take a yearly toll in injured fish. On rare occasions the devil rays bathers. Some skates are found off the appear to scoop up their prey with the coasts of the northern European coun- help of the cephalic extensions of their tries in sufficient abundance to support pectoral fins, and folk legend, ap- small but continuous foodfish fisheries. parently based on fact, states that they will even wrap their wings around The larger skates and rays are ap- anchor cables. parently less numerous, but our knowl- edge of their abundance is based, for The electric rays and torpedoes the most part, on incidental sightings possess the structural organization and of these creatures from coastwise the ability to transmit an electrical vessels. Claims of great local abun- shock. The mechanism by which this is dance of eagle rays, mantas, and simi- achieved is not completely known. It lar fish are often based more on the appears to involve an increase in great amount of publicity given a few activity of the nerve-muscle complex, sightings than on actual numbers. common to all animals. Release of a demonstrable electric discharge is a Size heightened example of a prevalent phe- nomenon. A nervous response involves The mantas, reputed to reach a an electrical impulse traveling along a breadth of 2Z feet and a weight of over pair of nerve fibers and acting upon 3,000 pounds, are the largest fish of the a section of the brain (at one end of the group. Sawfishes are also quite large circuit) and a muscle (at the other end). and may reach a total length of 22 feet, The "electric organ" of torpedoes is a although actual verified records do not wing- shaped mass of modified muscle exist for specimens this large (see tissue, richly innervated, lying in the table on the inside cover). At the other forepart of the body on either side of end of the range there are a few species the vertebral column. A so-called of ray and torpedoes that never exceed "electric lobe" in the brain completes a few inches in breadth. the nerve pathway. Textbooks of com- parative or general physiology may be Food and Feeding Habits consulted for further particulars. Most skates, rays, and closely re- lated forms are bottom feeders, and The Atlantic torpedo, a relatively , , other crustaceans, large ray which reaches a length of clams, and worms constitute their nearly 6 feet and may occasionally principal food items. Many skates cap- weigh as much as 100 pounds, is said ture prey by swimming quickly above to have produced a discharge amounting the victim, dropping down on it, and to 220 volts. This is probably very preventing its escape by covering it nearly the maximum discharge to be with their winglike fins. Some of the expected from a ray and is much less more sluggish rays appear to lie in than the maximum reported for electric wait for their prey- -half covered with eels. Very little is known about the sand, and many of the members of the discharges of other electric rays and group seem to prefer to feed only at torpedoes, except that the discharges night. of the electric ray are pulsed and de- livered in rapid succession--very simi- Sa'wfish feed primarily on and in the lar, in principle, to the mechanism used bottom, which they scrape and dig up in present-day applications of elec- with their saws, but they also feed in tricity in commercial fishing. Exami- open water, where they capture their nation of stomach contents of a number prey by slashing their sa'ws around in of electric rays and torpedoes suggests the midst of schools of fish. that the discharges are used in food getting, for the size of many of the A few rays- -principally the devil fishes found in stomachs is larger than rays and mantas- -feed on pelagic would be expected on the basis of more , mysids, and small school ordinary means of capture.

12 Anatomical Features the -wound resulting from a ray- spine puncture is apparently attributable to Perhaps the most outstanding ana- secretion of poison in at least a fewr tomical feature of many members of instances, but is also due to the ac- the group is the wide expansion of the cumulated covering of dirt, slime, and pectoral fins, a feature which gives the bacteria that clings to the spine, to the fish a disclike shape. The gill openings configuration of the wound, and to the are entirely on the ventral surface, with jagged nature of the cut. Owing to the no portion of them extending above the deep-puncture character of the spine plane of insertion of the pectoral fins. wound, conditions are optimal for gan- The sharklike rays, including the saw- grene. fish and the guitarfish, are classified as true rays on the basis of gill posi- Examination of the mouths and tion, certain differences in skeletal tooth structure of rays and skates pro- structure which seem to more nearly vides ready explanation of how some of ally them to rays than to sharks, and a these creatures can feed upon hard- few other, possibly more obscure, shelled crustaceans and nriollusks. Un- characteristics. like the teath of most sharks, which are Several species of rays that inhabit pointed, sharp, and fitted for tearing, shallow water are provided with long, the teeth of the typical rays and skates sharp spines on the base of their tails. are blunt, platelike, or arranged like a These spines are capable of inflicting pavement over the jaws and well- suited serious injuries on persons coming in for crushing. Jaw musculature is cor- contact with them. The seriousness of respondingly powerful.

A 'Typical" r.iy, the roughtail stingray, Dasyatis centrouro. This specimen measured 62 inches across the fins and weighed 285 pounds. Such rays are taken frequently in trawl drags along the east coast of the United States.

13 Relation to Man but with less vitamin-A content than sharks. Rays have never been as innportant, commercially, as sharks; but small Danger from stingray wounds has fisheries for rays are in existence in been discussed. Stingrays are found many parts of the world. The meat of most often along quiet, muddy shores. the wings (pectoral fins) is said to be The spines of stingrays have provided of excellent quality, but little market- primitive peoples with weapons, and ing of ray meat is done in this country. even today, in some countries, there Some of the larger skates and rays are laws prohibiting or limiting the contain appreciable quantities of oil possession of stingray spines.

CHIMAERAS Numbers and General Distribution group is so little known. Surely, com- pared with the bony fishes, they are Only about 2 dozen species of this infrequently observed or collected, but group are recognized at the present this may be, in part, a function of dif- time. This number will, perhaps, be ferences in distribution or reaction to added to as deep-water and midwater collecting gear. The chimaeras ap- oceanic investigations become more parently occur in a "patchy" distribu- comprehensive. tion pattern, and when and where present, they often are relatively abun- are worldwide in dis- Chimaeras dant. Much more work remains to be and are found in almost all tribution done before problems of chimaera subtropic, temperate, seas--tropic, distribution are completely resolved. and boreal. In most instances, how- In some parts of the world, the fishes they appear to be limited to the ever, are sufficiently abundant to form the water masses. For that reason, cooler basis for small fisheries. In the north- and subtropic seas, they in the tropic western Atlantic (along the eastern are generally found in the deeper and coast of the United States), the group therefore cooler depths or in cold is known only from isolated specimens have beenfound upwellings. Chimaeras collected with small scientific gear. the surface to depths of ap- from near Gulf of Mexico, several speci- Veryprob- In the proximately 1,500 fathoms. mens have been trawled on or beyond ably they exist in deeper waters also. the edge of the , and Abundance where they were taken at all, they ap- pear to be found in aggregations. Off It is difficult to assess the abun- Puerto Rico, in the Caribbean, small dance of the chinnaeras because the aggregations also appear to be present.

Sensory mucous

|5^- Dorsal Rn 2^ Dorsal Fin

Upper Caudal Fin

Pectoral Rn Lower Caudal Fin Caudal Rloment- Single Gill opening

A generalized chimaera illustrating ternts used in description,

14 On the west coast of the country, back into which the spine and the first there are a few shallow-water repre- dorsal fin can be folded, and a straight, sentatives of the group which are thin macrouridlike tail (hence the locally abundant. common name "ratfish" for both the bony-fish group Macrouridae and the Size chimaeras).

In contrast with the wide size Chimaeras breathe by taking in ranges exhibited by sharks, skates, water through their nasal apertures, and rays, the chimaeras constitute a passing it over the gills through respir- relatively uniform size group, with atory channels (and removing part of extremes placed just below 2 feet at the oxygen from it), and sending it out maturity to a little over 6 feet. through the single openings on either side. Food and Feeding Habits Chimaeras rest on the bottom at The chimaeras are carnivorous irregular intervals. When doing so, and therefore predacious, as are most they are said to use the tips of the members of the class Chondrichthyes. large pectoral and pelvic fins as Chimaeras, however, are feeble "props" to support themselves off the swimmers and are selective in their softer substrates. feeding only to the extent that they feed upon animals with limited powers Relation to Man of escape- -principally small fish and . In the Orient, where In the Pacific Northwest of the they are fished with handlines, they United States, there is a minor fishery apparently bite a wide variety of baits. for chimaeroids; the liver oil has a small commercial value. In some other Anatomical Features parts of the world, however, the fish are used on a large scale, owing to Two out of three families of chi- their greater availability, high oil con- maeras are characterized by oddly tent, and edible quality. The fish form shaped prolongations of their snouts, the basis for an industrial oil fishery whereas members of the third family in some Scandinavian countries and a possess gently rounded noses. These foodfish fishery in New Zealand as well rostral characteristics have been re- as in China and some other parts of sponsible, in large, for the various the Orient. common names applied to the group, including "goat fish", "elephant fish", Chimaeras present little or no "rabbit fish", and others. Chinnaeras danger to humans, for despite their are also characterized by their large, ability to bite rather viciously, they weak fins, a large spine in front of the are usually either dead or dying when first dorsal fin, a groove along the pulled from the water.

15 ANNOTATED LIST OF REFERENCES

The literature on sharks, skates, rays, and chinaaeras is voluminous and connposed of contributions from all major countries of the world. The list of references following can only provide a glimpse of the total. The reader may scan the bibliographies of the works consulted for further clues as to the nature and extent of literature.

Because zoology is a dynamic subject, zoological literature is constantly increasing in volume, and zoological concepts are constantly undergoing modifi- cation. Some of the most innportant current references are, therefore, found in journals rather than in textbooks.

GENERAL REFERENCE BOOKS sharks, or groups of sharks, are se- lected as general owing to the large The following books should be re- amount of discussion of a more general garded as basic references for the nature that has been included in them: serious student of elasmobranchs: OLSEN, A. M. 1954. The biology, migration, and BIGELOW, HENRY B., AND WILLIAM growth rate of the school shark, C. SCHROEDER. Galeorhinus australis (Macleay) 1948. Sharks, /n F i s h e s of the (Carcharhinidae) in western North Atlantic. Sears south- Foundation Marine Research eastern Australian waters. Australian Journal of Ma- Memoir No. 1, pt. 1, p. 59-576. rine and Freshwater Re- search, vol. 5, no. 3, p. 353- 1953. Sawfishes, g u i t a r f i s h e s, 410. skates, rays, and chimaeroids. Fishes of the western North RIPLEY, E. Atlantic. Sears Foundation Ma- WILLIAM 1946. The biology of the soupfin rine Research Memoir No. 1, Galeorhinus zyopterus and bio- pt. 2, XV 588. chemical studies of the liver. The soupfin shark and the These two companion volumes, although largely systematic in scope, summarize most of the information fishery. California Division of available at the time of printing on habits, food, size, Fish and Game, Fisheries Bul- abundance, reproduction, and distribution of the known letin 64, p. 6-37. chondrichthoid fishes in the western North Atlantic. SPRINGER, STEWART. NORMAN, J. R., AND F. C. ERASER. 1960. Natural history of the sand- 1938. Giant fishes, whales and dol- bar shark Eulamia tnilberti.U. S. phins. Putnam, London, xxii Fish and Wildlife Service, + 376 p. Fishery Bulletin, vol. 61, no. 178, 1-38. A general and popularized iccount of the size, p. habits, and occurrence of the common large marine Discusses the natural history of a common shark of animals. the coastal waters oftheeastcoastofthe United States, with many comments applicable to elasmobranchs in general. GENERAL REFERENCE PAPERS-- NATURAL HISTORY STRASBURG, DONALD W. 1958. Distribution, abundance, and The following papers, although habits of pelagic sharks in the dealing primarily with particular central Pacific Ocean. U. S. Fish

16 and Wildlife Service, Fishery BEEBE, WILLIAM, AND JOHN TEE- Bulletin, vol. 58, no. 138, p. 335- VAN. 361. 1941. Eastern Pacific Expeditions

Discusses the natural history of 12 species of oceanic of the Zoological So- sharks on the basis of observations made in the course ciety. XXV. Fishes from the of longline tuna fishing cruises. The only paper of its tropical eastern Pacific. (From sort dealina with shartc popuUuions of offshore waters. Cedros Island, Lower California, TEMPLEMAN, WILFRED. south to the Galapagos Islands and northern Peru). Pt. 2, 1944. The life-history of the spiny Sharks. Zoologica, vol. 26, no. 2, dogfish (Sqimlus acanthias) and p. 93-122. the vitamin A values of dogfish liver oil. Newfoundland Depart- BIGELOW, HENRY B., AND WILLIAM ment of Natural Resources Re- C. SCHROEDER. search Bulletin No. 15 (Fish- 1953. Fishes of the Gulf of Maine. eries) p. 1-102. U. S. Fish and Wildlife Service, Fishery Bulletin, vol. 53, no. 74, GUIDES TO THE CLASSIFICATION viii + 577 p. AND NAMING OF CHONDRICHTHOID FISHES CLEMENS, W. A., AND G. V. WILBY. 1946. Fishes of the Pacific coast of AMERICAN FISHERIES SOCIETY. Canada. Fisheries Research 1960. A list of common and scien- Board of Canada, Bulletin No. tific names of fishes from the 68, 368 p. United States and Canada. 2d ed. American Fisheries Soci- FOWLER, HENRY W. ety, Special Publication No. 2, 1941. The fishes of the groups Ann Arbor, 102 p. Elasmobranchii, Holocephali, Isospondyli and Ostarphysi ob- Lists the common and scientific names of the most tained by the U. S. Bureau of common jawless, chondrichthoid, and teleostenn fishes Fisheries steamer "Albatross" and indicates the general area of distribution of each. in 1907 to 1910, chiefly in the Philippine Islands and adjacent REGIONAL KEYS AND GUIDES TO seas. U. S. National Museum, IDENTIFICATION Bulletin 100, vol. 13. x + 879 p.

The following paper s provide lists, HILDEBRAND, SAMUEL F., AND keys, discussions, or guides to the WILLIAM C. SCHROEDER. identification of chondrichthoid fishes 1928. Fishes of Chesapeake Bay. in the areas indicated in the titles. In Bulletin of the U. S. Bureau of most cases, the papers have an even Fisheries, vol. 43, pt. 1, p. 1- wider range of applicability (in a geo- 366. graphical sense), as many elasmo- branchs are far-ranging animals. Be- JORDAN, DAVID STARR, AND HENRY cause the subject matter of these papers W. FOWLER. is described so aptly in the titles, no 1903. A review of the elasmo- further annotation is given in this sec- branchiate fishes of Japan. Pro- tion. ceedings of the U. S. National Museum, vol. 26, no. 1324, BAUGHMAN, J. L., AND STEWART SPRINGER. p. 593-674. 1950. Biological and economic notes on the sharks of the Gulf of RADCLIFFE, LEWIS. Mexico, with especial reference 1916. The sharks and rays of Beau- to those of Texas, and with a key fort, . Bulletin of for their identification. Ameri- the U. S. Bureau of Fisheries, can Midland Naturalist, vol. 44, vol. 34, Doc. no. 882, p. 241- no. 1, p. 96-152. 284.

17 ROEDEL, PHIL M., AND WILLIAM HYMAN, LIBBIE H. E. RIPLEY. 1942. Comparative vertebrate anat-

1950. California sharks and rays. omy . 2d ed. University of Chicago California Division of Fish and Press, Chicago, 544 p. Game, Fishery Bulletin 75, p. 1-184. NORMAN, J. R. ROSENBLATT, RICHARD H., AND 1949. A history of fishes. A. A. WAYNE J. BALDWIN. Wyn, Inc., New York, 463 p. 1958. A review of the eastern Pacific sharks of the genus A generalized account of the anatomy and lives Carcharhinus, with a of redescrip- the fishes. tion of C. tnolpaloensis (Fowler) and California records ofC. ROMER, ALFRED SHERWOOD. rc7notus (Dumeril). California 1949. The vertebrate body. W. B. Fish and Game, vol. 44, no. 2, Saunders Co., Philadelphia, viii p. 137-159. + 643 p. SCHULTZ, LEONARD P., EARL S. HERALD, ERNEST A. LACHNER, A Standard textbook of comparative ARTHUR D. WELANDER, AND vertebrate anat- omy. Contains a discussion of the anatomy of the dog- LOREN P. WOODS. shark. 1953. Fishes of the Marshall and Marianas Islands. U. S. National Museum Bulletin 202 (vol. 1), PHYSIOLOGICAL REFERENCES p. 1-685.

SMITH, J. L. B. HEILBRUNN, L. V. 1950. The sea fishes of southern 1952. An outline of general physiol- Africa. Central News Agency, ogy. 3d ed. W. B. Saunders Co., South Africa, xvii + 564 p. Philadelphia, xiv + 818 p.

TORTONESE, ENRICO. A technical treatise dealing largely with physiology at the cellular level. Chapter 29, "Tlie Production of 1956. Fauna d'ltalia. Vol. 2, Lepto- Electricity" and Chapter 30 "Biolummescence" are cardia, Ciclostomata, Selachii. recommended. Edizioni Calderini, Bologna, p. 1-332. NICOL, J. A. COLIN. WHITLEY, G. P. I960. The biology of marine ani- 1940. The fishes of Australia. Part mals. Sir Isaac Pitman and Sons, 1, The sharks rays, devilfish Ltd., London, xii + 707 p. and other primitive fishes of Australia and New Zealand. A general reference on ecological physiology of of Royal Zoological Society New marine animals including members of the class South Wales, Sydney, p. 1-280. Chondrichthyes.

ANATOMICAL REFERENCES PROSSER, C. LADD (editor). 1950. Comparative animal physiol- ogy. W. B. Saunders Co., Phil- DANIEL, J. FRANK. adelphia, X + 888 p. 1934. The elasmobranch fishes. University of California Press, A comprehensive text covering the animal kingdom, Berkeley, 332 p. specific sections on nutrition, foods and feeding, excre- tion, metabolism, circulation, chemoreception, photo- Devoted exclusively to a discussion of the anatomy reception, muscle and electric organs, biolumines- of sharks, skates, and rays. cence, nervous system and other subjects.

18 REFERENCES ON THE RELATION GILBERT, P. W., L. P. SCHULTZ, OF SHARKS TO MAN AND STEWART SPRINGER. 1960. Shark attacks during 1959. COPPLESTON, V. M. Science, vol. 132, no. 3423 (Au- 1958. Shark Attack! Angus and gust 5), p. 323-326. Robertson. Sydney. 266 p. LLANO. GEORGE A. 1957. Sharks v. men. Scientific A genera] account of damage wrought by sharks and American, vol. 196, no. 6, p. 54-

of their attacks on man, 6 1 .

MS #1070

19

ft U.S. GOVERNMENT PRINTING OFFICE; 1961 O - 607626

TABLE 2. —Maximum length and widths of common species of sawfishes, guitarfishes, skates, rays and chiraaeras

Species