THE ROUNDMOUTHS—LAMPREYS AND HAGS
Popularly included among fishes, the lampreys and hags of the class Cyclostomata (roundmouths) differ from true fishes by the possession of a suctorial mouth devoid of functional jaws, by the single olfactory organ, and by the absence of lateral appendages, or paired fins. They have an eellike form and method of travel, and some species are a yard in length. They are bisexual, discharging both eggs and milt into the water to become fertilized by accidental contact. Lampreys ascend the rivers to spawn, however, and there make little heaps of pebbles, carried and piled with the mouth, in which the eggs find some protection from the many egg-eaters in all streams. Most, if not all, of the migratory parents die after spawning. From the eggs hatch larvæ that undergo a metamorphosis. Lampreys live on small crustaceans, worms, and so forth, eat carrion, and also attack living fishes. The tongue, like the interior of the mouth, is armed with teeth. They are in the habit of attaching themselves to stones in order to hold themselves against a river current, breathing meanwhile by taking water directly into the pouchlike gill chambers and expelling it, instead of sucking it through the mouth and passing it out of the gill slits. In ancient Rome the big sea lampreys of the Mediterranean were eaten as a delicacy, and even cultivated in landlocked ponds, and they are still highly prized in some parts of Europe.
The hags are an even more primitive group of cyclostomes that live in the mud of shallow seas and are too abundant on both our coasts, where they are a pest of the fisheries. Their general habits are similar to those of lampreys, but wherever possible they attach themselves to fish on which they feed. The hag is particularly destructive to fishes caught on "set lines" of hooks, or in nets, and the loss thus resulting on the coasts of California, in Japan, and in some European fisheries is very serious. As these cyclostomes have no scales or other hard parts to be preserved except a few teeth, no fossil remains are certainly known, but it is the opinion of paleontologists that otherwise the class might be traced to the earliest Paleozoic time.
[CHAPTER XIII]
FISHES—THE ARISTOCRACY OF THE WATERS
In beginning, with the fishes, an account of the typical vertebrates, it will be well to point out the structural features in which all agree. Vertebrates are bilaterally symmetrical animals, with an internal skeleton, the axis of which is composed of similar segments (vertebræ) and divides the body into a dorsal and a ventral portion. This skeleton is first formed in cartilage, and remains so, or it may become more or less hardened by deposits of lime, or completely transformed into bone. The anterior end of the vertebral column (backbone) carries a capsule (the skull) inclosing the brain. When limbs are present there are never more than two pairs. The nervous system consists of a brain and spinal cord from which trunk nerves arise and ramify throughout the body. The blood is first driven to the gills, or to the lungs, as the case may be, by means of a heart having either one or two auricles, and after it has traversed the body through arteries and veins it returns to the heart. The stomach, liver, and other viscera, lie in the ventral part of the body. The skin produces a protective covering characteristic in each division of the class, as scales for fishes, feathers for birds, and so forth.
Fishes are vertebrates fitted to live in water. Their typically fusiform shape is that best adapted to progress through the rather dense medium they inhabit; and their limbs are swimming organs, or "fins." These are of two kinds, "paired" and "median." The former are the pectorals, one on each side of the forward part of the body, and the pelvic, or ventral fins on the belly and near together; these four serve, like the bilge keels of a ship, to maintain stability—prevent rolling over—rather than for progression. The median fin is vertical, and extends around the tail from the middle of the back to the end, when it is complete; but in most cases it is represented by an upright fin, the "dorsal" on the back, by the "caudal" fin fringing the tail, and by the "anal" fin at the vent. The powerful caudal fin is the principal agent in swimming, aided by undulatory movements of the dorsal and ventral fins; and it has a twisting action that drives the animal forward as does the rolling of the oar in "sculling" a boat. The median fins are developed from the skin, and are supported by a skeleton system of their own, not connected with the spine. In most fishes the upper and lower halves of the caudal fin are alike, and the tail is symmetrical, but in sharks and some others the end of the spine curves upward and the lower wing of the tail is much larger than the upper; in the former case the caudal fin is said to be "homocercal," and in the latter "heterocercal."
The fins of fishes are in many species modified and adapted to purposes remote from swimming or balancing. Thus it is the first dorsal fin of the remora that has become the sucker on its crown; in the angler the first rays of the back fin are lengthened and lobed to form its "lure," and elongation of various fin rays as feelers, or light bearers, etc., may be found elsewhere. The pectorals are enormously enlarged to make wings for the flying fish and the gurnard, and to give a substitute for legs to the Oriental gobies that like to go ashore, while the ventrals are transformed in certain fishes of swift streams into organs by which they can fasten themselves to the bottom or climb against a cataract.
The skin of fishes is rather thick and tough, and abounds in glands that secrete mucus, and in cells that secrete the hardening, or protective, denticles and scales that form the coat of most species, and which differ widely.
Louis Agassiz distinguished four kinds of scales—placoid, ganoid, cycloid and ctenoid. The first named occur only in the selachians (sharks and rays) and are variously shaped particles of lime that prick through the skin, which makes excellent polishing material when prepared as "shagreen." These "denticles" in the skin become teeth in the mouth without change of structure, and the great spurs with which the "saw" of the sawfish is armed are only extreme instances of this special adaptation.
Ganoid scales are such as formed the armor of the great extinct tribe of ganoid fishes, a remnant of which survives in our gar pikes, or billfish. In some of the fossils they are roundish, and overlap, but in modern ganoids they are rhombic in shape and plate the body edge to edge, connected by toothlike processes that articulate with the adjacent scales, and permit flexibility in the body. The outer face of the scales is enameled, like teeth, beneath which is a layer of bone substance and the teeth in the mouth are only modified scales.
Cycloid and ctenoid scales are those of ordinary fishes, and are precisely alike, except that the hinder, or attached, end of the latter is split into a comblike fringe. They have a rounded or often polygonal form, are composed of lime, and are translucent, thin, elastic, and overlap like shingles on a roof. The scales of fishes increase in size with the animal's growth by additions to the exposed rim, and as these accessions may be observed, by counting them the age of the fish may be computed, when checked by certain other considerations.
The colors of fishes are produced by pigment cells, both in the skin and on the outside of the scales; and by a peculiar tissue composed of secretion products called "iridocytes." These, by their various ways of reflecting light, and by the color elements contained in them, give rise to the different hues of fishes.
Fish show their inferiority as a class by retaining the method of respiration by means of gills characteristic of the aquatic invertebrates. The gills are composed of bright red tassels set on hoops that encircle the throat, and are usually covered by a movable flap—the "gill cover." Under this flap, the neck of the fish is perforated by crescentic slits. The fish normally breathes by taking gulps of water into the mouth and throat, and squeezing it out through the gill slits; during its rhythmical passage over the thin gills the oxygen of the dissolved air is absorbed by the hæmoglobin of the red blood, and is carried away to incessantly revivify the body; and at the same time carbon dioxide is set free and got rid of in the outgoing stream.
An organ peculiar to fishes is the air bladder—a sac lying under the backbone and communicating by a duct with the stomach. It is not only of service in respect to buoyancy, but is accessory to respiration. In spite of its name, however, it does not contain air, but a gas rich in oxygen and nitrogen which is secreted by certain arteries and is carried away when needed by other blood vessels, as fat and starchy substances are stored elsewhere and may be drawn upon when food falls short. Nevertheless, the chief function of the "swim bladder," which is exceedingly varied in shape, is to render the fish of the same weight as the water in which it lives. In this condition of equilibrium the fish swims with a minimum of muscular effort. A consequence of the organization, however, is to restrict the vertical range of each fish and kind of fish, because any considerable movement up or down means a change of pressure. This will bring about the expansion or contraction of the volume of gas in the air bladder and thus alter the specific gravity of the animal. Such automatic adjustment is limited, however, and practically prevents a fish rising or falling far above or below the depth to which it was born; and the fatal effects of violent change are seen in those fishes brought up in explorers' dredges from great depths, the air bladders of which are invariably so distended as to kill the animal. Nevertheless, some species seem able to migrate from and to great depths; and temperature is perhaps a greater factor in vertical distribution than the air bladder, the adjustments of which must be slow. The great body of fish life in the sea resides within about 300 fathoms of the surface.
Fishes have a brain and a system of nerves and sense organs varying according to rank, and outlining the higher developments of the nervous system as found in mammals. Of the sense organs the most peculiar are the small sensitive bodies scattered in various parts of the skin, fins and mouth, called "end buds," each at the terminus of a nerve fibril. These buds seem to carry the sense of feeling, and are said to be represented in mammals by the taste buds in our tongues. They are aggregated in a narrow band along the side of the fish, and in a maze on the side of the head, called the "lateral line," the course of which is plainly visible on many fishes, as for example, on the sunfish of brooks and ponds. This lateral line consists of canals in the skin, opening to the surface by pores, and reached by branches of large nerves. The use of the lateral line to the fish is not well known, but it is believed that its cells are of service in balancing the body. As blind fishes are able to avoid obstacles with the greatest ease when swimming, it is possible, in the opinion of Dr. Bridge, that these organs enable their possessors to appreciate undulatory movements in the water in the shape of reflex waves from contiguous surfaces or objects.
One feature of the lateral line on the head are the "auditory organs," varying with the kinds of fish, which contain semicircular canals, with otoliths, in the more or less complete form of an internal ear. Each is reached by the auditory nerve from the brain and is also connected with the air bladder in many cases. Whether this is a true organ of hearing in the ordinary sense, or whether it serves some other purpose, as, for instance, the regulation of the distension of the air bladder, is not known. The old question of whether fishes hear sounds made above the water is not yet answered scientifically; but it is probable that they can feel the jar of sounds made in the water, which is equivalent to hearing, as far as it goes. Fishermen have a saying that if you swear you won't catch any fish—a good precept, anyhow; but more effective is the care anglers take not to step heavily, nor to make loud, jarring noises, near the bank of the stream in which they mean to cast their lines.
The great majority of fishes have good eyesight, and the eyes themselves are similar in structure to those of the higher land animals; but it seems probable that the range of vision is short. The eyeballs are usually large in proportion to the size of the head—sometimes strikingly so—and are movable; while the situation in the head is naturally such as to give the most advantageous vision according to the habit of life. Thus those of sharks, and other predatory sorts that live by the chase, are well forward; while those of bottom-feeders, and especially rays, flatfish, anglers and the like, are in the top of the head, looking upward. Nocturnal species have the largest eyes, but the unfortunate cave fishes, whose whole life is, and has been for unnumbered generations, passed in the total darkness of caverns and underground streams, have lost the use of their eyes altogether, and the organs themselves have disappeared by atrophy.
Blindness is found also in oceanic families that dwell far below the penetration of daylight; yet many fish of the Stygian depths, which, so far as we know, never leave that region of utter blackness, possess big and apparently efficient eyes. Most of the blind or nearly blind sea fishes thus far obtained have been in hauls from a depth of about 1,200 fathoms. It is believed that the ability to see in deep-sea fishes is connected with the light-giving (phosphorescent) organs possessed by many of them, and with the fact that animals of all sorts on the sea bottom in deep water are luminous, and so reveal themselves to the predatory creatures that feed on them, while the fishes' own "lanterns" enable them to chase moving prey, avoid enemies, and find mates.
Fishes have efficient olfactory organs situated near the snout, and in the higher families they are in pairs and become true, but internal, nostrils. The sense of smell is strong, and perhaps more useful on the whole than the sense of sight, especially among the carnivorous species. Sharks seem to follow their prey by scent like hounds.
All these senses serve instincts related to the necessities of the individual and the race in each kind of fish. This is sometimes manifested in what appears to us as cunning means of safety or of provision for young; but discriminative intelligence is small in fishes, which probably are able to learn little more than that at certain places and times food may be had, as is illustrated in cultivated fish ponds, where the captives from infancy onward are fed regularly. Anglers tell of old trout that refuse year after year to be beguiled by their experiments in flies; but it is doubtful whether this is anything more than an increased wariness due to frequent disturbance. The remora is, or has been, used by the Caribs of the West Indies and the negroes of Zanzibar for catching sea turtles, a line being fastened to a captive and comparatively tame remora carried in the boat, and the fish turned loose as soon as a turtle is seen at the surface. The remora will make a bee line for the turtle and attach itself firmly to the shell so tenaciously that both animals may be dragged to the boat. It is to be noted that the fishermen see the turtle near by before they dispatch their living grapple, and it is doubtful whether the remora has any notion of what it is doing. It simply obeys repeatedly an instinct. This very low degree of intelligence is doubtless owing to the almost invariable environment of piscine lives, in which virtually nothing occurs to suggest any change in traditional habits or arouse into activity any rudiments of mind a fish may possess. Mental inertness is characteristic of aquatic animals of all kinds, as contrasted with the correlated activity of body and mind of land animals stimulated by varied and changeable surroundings.
The breeding habits of fishes furnish one of the most interesting chapters in their natural history, and many surprising facts have been learned within a few years in regard to the reproduction of marine species, of great value to the sea fisheries.
In all fishes the sexes are separate. As a rule females are larger than males, and more numerous. The size of the egg in any group depends on the amount of food yolk stored for the sustenance of the young, which must thrive by its absorption until it is able to eat by its mouth. The largest are the eggs of sharks, etc. (Elasmobranchii), which resemble fowls' eggs. The European dogfish, perhaps two feet long, has eggs an inch in length, each in a flattened leathery "purse" having tendrils at the ends that twine about weeds and anchor it like a rocking cradle. The similar egg capsules of skates, dropped on the sand, are common objects on all beaches. Elasmobranch eggs are deposited at intervals throughout the year and, as they are exposed to comparatively little danger, are few in number. In most other orders spawning, as the egg laying of fishes (and aquatic amphibians) is termed, is limited to a short period, the eggs are small, and the number of eggs produced is often enormous—five or six millions in a large cod, for example.
In the majority of Teleostomi—a group name embracing all the modern bony fishes—the eggs are voided broadcast into the water, the males at the same time emitting clouds of milt. These eggs are of two kinds, one that sinks and, often being glutinous, sticks to some object on or near the bottom, and is called "demersal"; and another that contains an oil bubble, making it so buoyant that it floats, and these latter are called "pelagic." The fertilization of such spawn must be accidental, but as the milt and the eggs sink or drift together the number that come into fertilizing contact is no doubt considerable. Nevertheless, an extremely small percentage ever reach the point of hatching, and still fewer survive to become mature, for in addition to unfavorable circumstances of water and temperature, every living thing, almost, in the ocean, including the parent fish themselves, is a devourer of the eggs and young of fish; and it has been said that the vast number of eggs dispensed by certain species, only a single pair of which on the average survives to maturity, is one of nature's methods of providing food for the inferior forms of marine life.
[CHAPTER XIV]
SHARKS—THE TIGERS OF THE SEA
Only a rapid systematic sketch of the class Pisces, fishes, is possible, distinguishing the main divisions, alluding to their history, and touching here and there the most characteristic genera and species of the thousands that have been described by ichthyologists. The primary division is into three subclasses:
1. Elasmobranchii—Sharks, skates, rays, etc., having a cartilaginous skeleton.
2. Teleostomi—Ordinary fishes, having a bony skeleton.
3. Dipnoi—Lepidosiren, and many extinct, primitive families.
In the Elasmobranchii, or selachians, the skeleton consists of cartilage, as in the embryos of all fishes—a sign of their primitive and inferior rank; but parts of it in various species become hardened by depositions of lime, especially in the vertebræ, in spines and teeth, parts often well preserved as fossils. Sharks' teeth are among the best known of fossils, and before science established their true character were commonly called "birds' tongues," or "snakes' tongues." The sharks, first to be considered, are a very ancient race, originating in early Paleozoic times. Of the many curious extinct forms that terrorized the Silurian, Devonian, and Carboniferous seas, a few representatives still exist in the South Pacific, notably the cow sharks; an eellike Japanese species with frilled gills that Dr. Garman thought might easily fill the rôle of "sea serpent"; and the quaint bullhead, or Port Jackson sharks of Australian waters; all these are of small size and the last named represents the principal race in Mesozoic seas. Their flat teeth form a sort of pavement of the mouth, enabling them to crush the mollusks and crabs on which they chiefly feed.
Next in a rising order of classification, and of somewhat more recent origin geologically, is the European family of dogfishes (Scyllidæ), which includes also the "ground sharks" of warm seas—deep-water fish eight to twelve feet long, that creep about near the bottom in search of prey. Next come the large pelagic sharks of the family Carchariidæ, which contains about sixty species, scattered over all the seas, and one confined in the fresh water of Lake Nicaragua. One section, that of the "topes" and "hounds" of temperate and warm seas, are bottom-feeders, and have pavementlike teeth adapted to crushing and grinding the shellfish on which they subsist; but most of the family are swift and powerful hunters of fishes in the open sea, such as the dreaded tiger shark of the West Indies, which is variegated in color and sometimes twenty feet long, and the equally big blue, white, dusky, and other ferocious bandits ranging not only the tropical seas, but more common in northern oceans than is generally supposed. The teeth in these and other hunting, fish-catching sharks, are shaped somewhat like arrowheads, in some cases smooth-edged and single-pointed, in others with sharply notched edges and side cusps. They are set in the flesh of the jaw, unattached to the underlying bones, in concentric rows, one close behind the other, all round the front of the mouth, both above and below, and look and act like a set of saws, a sidewise movement of the jaws sawing through an object seized in a single bite. As fast as the front row of teeth are lost they are replaced by those of the row immediately in the rear. But all gradations exist between these and the mosaic of "pavement" teeth in the topes. The mouth of these hunting sharks is on the underside of the head, and they must turn on their backs to seize anything floating or swimming near the surface.
This is the group that furnishes the "man-eater" stories—tales that have been substantiated by so many terrifying examples that no precaution of safety against them should neglected, even on our northern coasts, where the ravenous blue shark, or the dusky species, may appear at any time, even in harbors. A few years ago a man was seized by one of these sharks in a little inlet of New York Bay, at Freeport, New Jersey.
Blue sharks are nocturnal in habit, and are sometimes seen asleep or resting in the daytime, with the tips of the two dorsal fins, characteristic of this family, in sight above the surface of the water. "So gentle are they in their movements," says one authority, "that, unlike many other monsters of the deep, they do not disturb the luminous creatures, which at the same time will be lighting every wavelet with their phosphorescence. Blue sharks are not very particular as to what fish they take as food, though those which are gregarious in their habits, like mackerel, pilchards, and herring, are most commonly hunted by them." A curious relative of these "man-eaters" is the hammerhead, in which the sides of the head are extended in two great lobes, with eyes at their extremities; this kind of shark is greatly feared in the East Indian seas. In spite of it, and the prevalence of other huge and voracious sharks, the Arabs about the entrance to the Red Sea, and the natives of other Oriental shores, will swim and dive in the open sea, apparently without fear, where Europeans would be devoured almost instantly. Another peculiar shark is the thresher, well known in the North Atlantic as elsewhere for its strategic maneuvers. It grows to a length of fifteen feet, of which the tail forms at least one half. Quite inoffensive to man, the thresher feeds on the shoals of smaller teleosts, such as pilchards, herrings, and sprats. When feeding it swims in gradually diminishing circles around the shoal, splashing the water with its long tail, and keeping the victims so crowded together that they become an easy prey. Hammerheads and their relatives, the "bonnet" sharks, frequently visit both our shores in summer.
The porbeagles are big, fierce sharks of the family Lamniidæ, the giant of which is Rondelet's shark, known to attain a length of more than forty feet. The triangular, saw-edged teeth of such a one measure nearly an inch across the base; but similar fossil teeth, and also others dredged from the bottom of the South Pacific, are much larger, indicating sharks beside which Rondelet's would be small, and in all probability these monsters survived to a comparatively recent date. A remarkable lamnoid shark of Japanese deep waters has the snout produced into a long, flat, flexible, leaflike blade.
Closely related sharks, almost as big, are well known in the North Atlantic. Two of them, the "bone" and the "basking" sharks, are killed by fishermen whenever encountered for the sake of the oil in their livers. The name of the second refers to its habit of loafing and sleeping on the surface on fine days, when a boat may go so near it that a harpoon may be planted in its hide before it will move. The real "basking shark," however, is a gigantic species of Rhinodon, of the Indian and South Pacific oceans, with a very bulky body that may exceed forty-five feet in length. Both of these ponderous fishes are sluggish, and are not dangerous to man, except that a blow of the tail may smash a boat when an attempt is made to harpoon them at close quarters. They feed on small fishes that go in shoals, and also, perhaps, on seaweeds.
The last sharks to be mentioned are American dogfish of the family Squalidæ (another family, Scyllidæ, are known as "dogfish" and "hounds" in Great Britain), which are numerous and greatly hated along both our northern coasts. The common gray dogfish of the North Atlantic and California coasts is the spiny one (Squalus acanthias), the larger females of which will weigh about eight pounds. It makes its home in deep water off the New England coast, approaching the shore when the mackerel come in and disappearing when they depart; but dogfish are to be found all summer in shoal places such as George's Bank, and irregularly in shore inlets. In the late autumn they become numerous on the Grand Banks, and stay there until the winter's cold drives them away into deeper water. Everywhere these small sharks are a nuisance to the fishermen, by tearing nets and by eating the cod, etc., hooked on the trawl lines. Formerly they were regularly hunted for the oil in their livers, which is especially valuable for certain purposes, as in harness making, but the price of this oil is now low, and the fishery has declined.
The economic use of sharks is not great except as producers of oil. The flesh is good food, but not popular. In China sharks' fins are a favorite substance for delicate soups and sauces, and a very large trade in catching sharks for their fins is carried on near Bombay, and in East Indian waters.
The ugly angel shark, with its squat, toadlike body, big, winglike side fins and thick tail, occupies an intermediate place between the sharks and the rays. It creeps along the bottom, and is remarkably voracious. The chimæra is another queer "monster" of the deep.
[CHAPTER XV]
THE FEARFUL DEVILFISH AND OTHER RAYS
The rays (order Raiæ) differ from the sharks superficially rather than in structure, where the most important difference is the position of the gill clefts, which are lateral in the sharks and ventral in the rays and skates, as the smaller members of the order are called. The majority of them have a flattened, depressed body, from which the broad, expanded pectoral fins are scarcely distinct, while the tail is usually long and slender, in one family so much so that they are known as "whip rays;" and in some a horny point at the tip is connected with a venom gland so that its pricking is poisonous, and these are called "sting rays." All the rays are carnivorous, but only the sharklike forms (sawfishes and the Rhinobatidæ) actively pursue their prey. The true rays live on the bottom and feed on shellfish and small fishes. Most of them bring forth a few young alive, but many lay eggs in squarish, oblong, leathery cases with tendrils at the corners by which they become moored to eelgrass, etc; they are frequently cast up on beaches, and go by the name of "sea purses," In the earlier stages the young ray is much like a shark, and the enormous development of the pectoral fins does not occur until nearly the time of hatching.
| CATERPILLAR PROTECTED BY FORM AND COLOR RESEMBLING THE TWIGS OF A TREE |
| SEA HORSE PROTECTED BY FORM AND COLOR RESEMBLING THE MARINE PLANTS AMONG WHICH IT LIVES |
The sawfishes, of which several tropical species are known, besides one common in the Atlantic and Mediterranean, are among the most remarkable of oceanic fishes. The body is slender, sharklike, and of great power. The head is flattened, and the snout projects into a hard, flat, sword-shaped beak, the edges of which are thickly studded with sharp teeth; and this singular weapon places all the large inhabitants of the ocean at the mercy of this powerful marauder—it is the worst enemy of whales, even, in the warmer seas, as is the "killer" in the Arctic region. With it the sawfish cuts and slashes, tearing off pieces of flesh, or ripping open the abdomen of its opponent, then seizing the detached pieces. One can easily picture to himself the slaughter when a sawfish dashes into a school of fishes, squids, or porpoises, and slashes right and left with his ripsaw of a beak. Some of the Oriental species reach, and even exceed, twenty feet in length, and Dr. Day, the Indian ichthyologist, says that such monsters have been known to cut bathers completely in two. The saw of a twenty-foot fish would measure six feet in length and a foot across the base.
| Photo, Elwin R. Sanborn, N. Y. Zoological Society |
| Photo, Ewing Galloway |
| ABOVE, THE GILA MONSTER, FEARED THOUGH ITS BITE IS NOT ALWAYS DEADLY TO MAN BELOW, THE IGUANA, A REMARKABLE LIZARD OF THE NEW WORLD |
The most famous of the rays, probably, are the torpedos, a family with a rounded, instead of the customary triangular outline, and a rather short tail, species of which occur on all tropical and temperate coasts, and are noted for their power to give electric shocks to any living thing touching them.
The electric organs are a pair of large masses lying between the head and the pectoral fins. These are derived mainly from four nerves, which originate from an electric lobe of the medulla oblongata. By means of the electric shocks which they are able to administer at will, the torpedo rays are able to ward off the attacks of enemies, and to kill or paralyze their prey. The action is that of a galvanic battery. The dorsal surface is positive, the ventral negative, and the discharge of a large torpedo is sufficient to temporarily disable a man; yet it is not so powerful as that from a big electric eel.
The huge "sea devils" of which thrilling stories are related are the eagle rays of the family Myliobatidæ, some of which are fifteen or twenty feet across the "wings"; and they are among the most frightful of the dangers to which pearl divers are exposed in their perilous occupation. They are savage beasts, and will even attack a small boat with men in it. The worst of these belong to the vicinity of Panama.
[CHAPTER XVI]
BONY FISHES—TELEOSTOMI
We come now to the fishes proper—those with skeletons of bone, although in some of the lower forms the ossification is incomplete. The mouth contains supplementary tooth-bearing bones that form secondary jaws corresponding to the functional jaws of the higher craniates; hence the group name "Teleostomi," or perfect-mouthed fishes. The body, as a rule, is coated with scales, and a gill cover (operculum) is always present.
The Teleostomi include four orders, the Crossopterygii, the Chondrostei, the Holostei, and the Teleostei.
The crossopterygians are mostly strange extinct fishes found as fossils from the Devonian down; but some have survived, and live in the sluggish African rivers an eellike existence, of which the bichir of the Nile is a familiar example. The Chondrostei also are largely fishes of the Paleozoic time, but two families survive to the present—the spoonbills and the sturgeons. Of the former one species is Chinese, and the other is the shovel-nosed spoonbill or paddlefish of the lower Mississippi River. It is a big, sluggish creature, that stirs up the mud with its long flat beak, and consumes it, getting sustenance from the minute organisms it contains. They make caviar from its eggs. As for the sturgeons, we have five species in the United States, and one abounds in the Black Sea and the rivers that drain into it, from whose eggs the Russian caviar is made. One or two species are exclusively fresh-water, but most sturgeons are migratory fishes, living in the sea, but ascending rivers for spawning. Their food consists of worms, mollusks, the smaller fishes and aquatic plants; and in feeding the mouth is protruded downward in the form of a cylindrical, spout-like structure and thrust into the mud. Our common eastern-coast sturgeon is also a native of the Mediterranean and French coasts, and was formerly in England a "royal" fish, reserved to the king's use.
Of the third order, Holostei or "ganoids," whose history may be traced in fossils almost to the earliest of fossiliferous rocks, we possess in our rivers the only two survivors: one is the many-named bowfin of the Mississippi Valley, and the other the widely distributed billfish or gar pike. Both these relics of a very ancient order are of great interest to naturalists; and the names "mudfish," "John H. Grindle," and many others, show how well known the bowfin is to the farmer boys. The bowfin attains a length of about two feet and a weight of twelve pounds, and, unlike its cousins the garfishes, is covered with hard, rounded scales; the forepart of the body is cylindrical, the head stout and blunt, and the mouth filled with powerful teeth. It is exceedingly hardy, enduring absence from the water for a long time, as well as grievous injury; hence the young are the favorite bait of anglers in the Mississippi Valley, and make interesting captives in an aquarium, where, however, nothing else but snails can remain alive. These fish are strong, active, voracious and gamy. They feed on all sorts of small aquatic creatures.
The garfish (or more properly gar pike, Lepidosteus, because certain sea fishes of another sort are also called gars) is an elongated active fish of our rivers, covered with hard, flat, ivorylike scales set in oblique rows, and its snout is prolonged into a bill filled with sharp teeth. They have many peculiarities of structure indicating their ancient ganoid lineage; and besides our common species two others are known, one of which, the alligator gar, belongs to the Gulf Coast and Central American rivers. These gars are nocturnal and predatory in their habits, and in early summer resort in large numbers to shallows to lay their eggs, which are covered with a sticky envelope that adheres to any object on which they fall. The long bill develops after infancy.
[CHAPTER XVII]
MODERN FISHES—TELEOSTEI
The lower orders of teleosts retain many characteristics of the Holostei, and several of their families are known only as fossils in the Cretaceous and Tertiary rocks. The most primitive survivor of these ancient forms is the great tarpon of Florida and southward, another species of which occurs in India—such wide differences in habitats being an evidence of antiquity in nearly all cases among animals. The extraordinary mormoids of northern Africa, and the eellike gymnarchus of Gambia, are other relics of the past, as also are several other queer African families, the barramundi of Australia, and the arapaima of the Amazon region. The one last named is the largest fresh-water fish known, specimens exceeding fifteen feet in length, and weighing 400 pounds, all of which is excellent food. The mother protects her offspring which, when young, swim in front of her. Several of these old-fashioned teleosts, like our bowfin and the primitive Dipneusti, make elaborate nests in which their eggs are deposited, and they and the fry are carefully guarded by the parent. In this same suborder come the most familiar and useful game and food fishes—the shad, herring, trout, salmon, whitefish, smelt, etc.
The shad family is a very large one, numbering about 200 species, most of which are marine, but a few are "anadromous," that is, they ascend rivers of fresh water to spawn in the shallows near their sources. This is the habit of American shad, of which there is only one species in spite of the many local names in use; and it is regarded by the fisheries authorities as the most valuable river fish in the country except the Chinook salmon; but the supply of it would have been exhausted long ago had it not been for the incessant and energetic methods of replanting of fry, artificially bred, in all the eastern rivers, and the transplanting of them to rivers on the Pacific Coast, the credit for which valuable public service belongs to the United States Bureau of Fisheries.
The shad is to be found from Florida to Newfoundland. Little is known of its life in the ocean, but in spring it approaches the coast in great numbers, and may be had in the St. John's River in Florida in winter, but it is not numerous until March. It next appears in the Savannah and Edisto Rivers, and so successively northward, the height of the run in the Potomac being in April, in the Delaware early in May, and in the Miramichi River in New Brunswick late in May. The main body ascends when the water temperature is 56 degrees to 66 degrees. They come in successive schools, the males preceding the females. They ascend the rivers, often nearly to their heads, and deposit their eggs on suitable spawning grounds, pouring out about 30,000 in most cases. The eggs are very small, semibuoyant, and usually require six to ten days for hatching, depending, as does the whole operation, on favoring temperature. After the spawning the shad show hunger, and will often bite at an angler's fly.
"The herring is beyond question the most important of food fishes in the Atlantic, if not in the world," declared the late G. Brown Goode, formerly Assistant U. S. Fish Commissioner. It affords occupation for immense fleets of boats, and thousands of men, nowhere more numerously than in the North Sea and along the Norwegian coasts. Professor Huxley once gave 3,000,000,000 as the number of herring taken annually from the North Atlantic; but Dr. Goode showed that this was far too low an estimate, and added that it probably was "no greater than the number contained in a single shoal if it covers half a dozen square miles, and shoals of much greater size are on record. And ... at one and the same time scores of shoals must be scattered through the North Sea and the North Atlantic, any one of which would go a long way toward supplying the whole of man's consumption of herring." Herrings are surface swimmers, and their food consists of the small organisms, chiefly crustaceous, which have been described as "plankton" in the early pages of this book. They themselves afford food to every predatory fish, squid, whale, and bird that frequents their region (mainly north of the fortieth parallel of latitude), and which has the wit and ability to seize them. They move here and there in shoals for food, and in spring migrate to the shallows and rivers of the northern coasts to spawn. Besides the Atlantic herring, a very similar species throngs in the North Pacific, and several others live in the Great Lakes and other waters of this country.
No fishes are better known in America than the salmon, trout, and whitefish, which are near relatives. Of the salmon there are many kinds in all the northern parts of the world and in the open ocean. Some ascend rivers to spawn, and some do not. Our Atlantic salmon, once so abundant in every river from Connecticut northward, is the same as the salmon of Europe, and the king of game fish. Now it is at all numerous only in the Maritime Provinces of Canada, climbing the waterfalls of those mountain streams to their very springs to deposit its eggs, whence few individuals survive to return to the ocean. The heaviest salmon on record is one of eighty-three pounds captured in England in 1821; an American example of forty pounds is considered very large.
The salmon of the North Pacific are of a different genus (Onchorhynchus) and consist of several species, some Asiatic. On the American side we have five species, and most of them have been seen in all the rivers from central California to Alaska, Siberia and Japan; but the blueback predominates in Fraser River and in the Yukon; the silver salmon in Puget Sound; the quinnat or Chinook salmon in the Columbia and Sacramento; while the comparatively worthless dog salmon is seen everywhere. The quinnat and blueback enter and "run" the rivers in the spring, and are caught when in prime condition, whereas the other three run in the fall, and are more usually caught after deterioration; hence "spring" salmon are best in fact and in trade.
The habits of the salmon in the ocean are not easily studied, but Jordan, Evermann, and other diligent students have come to certain conclusions from a great number of facts. They believe that the king and the silver salmon probably remain not far from the rivers where they were born. The blueback and dog salmon probably seek deeper water. It is the prevailing impression that the salmons have some special instinct which leads them to return to spawn on the same grounds where they were hatched, but Dr. Jordan says:
"We fail to find any evidence of this. It seems more probable that the young salmon hatched in any river mostly remain in the ocean within a radius of twenty, thirty or forty miles of its mouth. These, in their movements about in the ocean, may come into contact with the cold waters of their parent river, or perhaps of any other river, at a considerable distance from shore. In the case of the quinnat and the blueback, their 'instinct' seems to lead them to ascend these fresh waters, and in a majority of cases these waters will be those in which the fishes in question were originally spawned."
As to the fate of the spawning fish, after the eggs and milt have been voided, and their duty is done, the salmon begin to float downstream tail foremost. The great majority of them die—certainly all at the headwaters of the big streams; and it is the opinion of the best judges that none ever get back from anywhere alive into the ocean after spawning, but that the race is sustained wholly by the escape of the young each year. It is supposed that non return from the sea, or attempt to ascend the rivers until at least three years old.
Trout are in most cases simply small species of salmon, and a great number of kinds inhabit the ocean, lakes, and rivers of all northern countries, for none of this great family occur in the tropics or in the southern hemisphere. Our western trout—the widely distributed and variable cutthroat, the steel-head of the northwestern coast, the beautiful rainbow trout of the Coast Ranges, and others are examples. The common brown "brook" trout of Great Britain belongs here; but our brook trout, the "speckled beauty" of anglers and poets, is of a slightly different kind (genus Salvelinus), for it is classed with the European charrs. The Dolly Varden trout of the Rocky Mountains and the Sunapee trout are also charrs. The graylings, namaycushes, and smelts are members of this family, whose final representative among us is the numerous and very valuable section of whitefish and lake herrings of the Great Lakes and Canada generally.
No family of fish is of more importance as food for man, not to speak of the sport many of its members afford, than this; yet, doubtless, it would have been nearly destroyed by this time had it not been for the intelligent and patient work of fish culturists and the farsightedness of governments, both Federal and State, and Canadian, in supporting and extending economic replenishing of depleted waters. The organization and breeding habits of the salmon tribe lend themselves to this work.
Passing by some families of deep-sea fishes, of small size and most bizarre outlines, we come to the suborder that contains the carps, catfishes and "minnows" of our lakes and streams. Here, the first to present itself, in the large family Characinidæ, is that fierce little brute of South American rivers, the "piranha" or "caribe," of which Col. Theodore Roosevelt had so much to say in describing his explorations in Brazil in 1913 and 1914. One of his companions was Leo E. Miller, who has since published another account and increases the bad reputation of the caribe by what he has to tell of its ferocity:
"In the Orinoco they attain a weight exceeding three pounds, and are formidable indeed. The natives will not go in bathing except in very shallow water, and I know of two instances where men were attacked and severely bitten before they could escape. The fish somewhat resembles a bass in shape, although the mouth is smaller; the jaws are armed with triangular, razor-edged teeth; and as they travel in immense shoals they are capable of easily devouring a man or large animal if caught in deep water.... Usually they are slow to attack unless their appetite has been whetted by a taste of blood from a wound; then, however, their work is done with lightninglike quickness.... To catch them we used a large hook secured to a long wire leader and baited with any kind of raw meat, and they always put up a good fight."
A related fish in the Rio La Plata is almost equally dreaded because of its much greater size and formidable teeth, but it works singly; and Africa has many similar characinids, whose flesh is good food, though full of bones. In this order, too, is now classified the family of the "electric eels" (Gymnotidæ) which are not, however, eels, but merely long, cylindrical fishes, naked and almost finless. The well-known one of the Amazon region grows to a length of eight feet and the thickness of a man's thigh, and is justly feared. It is found only in marshes and in comparatively shallow parts of rivers, to the annoyance of travelers who have to ford at such points, beasts of burden being frequently knocked down by the electric shocks. About four-fifths of the length of the fish is occupied by the tail, which contains the electric organ. This consists of two huge masses filled with a jellylike substance, below the spine, and separated by a narrow median septum. This apparatus is under the control of the fish, which by it may stun or kill an enemy or an intended prey, even at a considerable distance.
The family of the cyprinids—the carp, goldfish, chubs, shiners, loaches, and other "minnows" of this and other countries—contains about 1,300 species, scattered over the whole world except South America, Madagascar, and Australasia. All are fresh-water fishes, feeding on vegetation and small animals; and they vary in size from two or three inches to a six-foot carp—the original home of which, now the cosmopolitan giant of the family, was Asia.
Next to these are placed another extensive fresh-water family, that of the catfishes (Siluridæ). More than 1,000 species, mostly tropical, have been described; these are grouped in eight subfamilies, among which there is a wide diversity in shape and habits—in fact, few of those of foreign lands look at all like the catfishes with which we are familiar in America. Most of them are sluggish, but some actively inhabit swift streams. They can exist not only in foul water, but will live a long time out of this element, and some even make long migrations overland from river to river. One or more fin rays are sharp and poisonous in many species, as boys know who handle the little bullhead incautiously, and an African species is able to administer a strong electric shock. Its apparatus is not a battery of modified muscular tissue, as in other electric fishes, but consists of a thick coat of greasy material surrounding the whole body just beneath the skin. Another general characteristic is the protection and assiduous care given to their eggs and young, most species making some sort of a nest in which the eggs are deposited and the fry kept safe from attack.
The third suborder of teleosts contains eellike fishes of the tropics; and the fourth contains the true eels and their relatives. Our common eel is also "common" in most of the temperate countries of the world, but there are perhaps 150 other species of the family Anguillidæ, a large proportion of which live altogether in the sea, many of them at great depths, and showing strange shapes. The generation of the eel was, until recent years, one of the great mysteries of zoölogy, as no propagation, or any symptoms of it, ever appear in fresh water. Finally it was discovered that a queer, almost transparent, compressed creature, a fraction of an inch long that abounded in the surface waters of the ocean, and which had been a puzzle to naturalists, who called it Leptocephalus, was the larva of some sort of eel. This and other discoveries made it plain that when the eels (of the age of four or five years) leave the rivers and bays of all countries and coasts in the autumn, and go out to sea, they do so to spawn, leaving their eggs on the floor of the ocean, mostly south of Bermuda, according to J. Schmidt. From them hatch the minute larvæ that, as they grow, rise to the surface, and when about a year old appear as the silvery young, called "elvers," that drift on the northward-running currents to the coasts of Europe and North America, and ascend the streams by millions in spring. It is not probable that any of the adult eels that go down to the sea to spawn ever come back; and if any remain in landlocked waters whence they cannot migrate to the salt water, they do not breed; but it must be remembered that eels are able to travel a considerable distance overland, at night, from one piece of water to another, and so many may finally reach the sea.
The next suborder illustrates the remarkable difference in size and external appearance that often marks fishes grouped together by similarity of structure. It includes the muskellunge and all the other pikes and pickerels, and the tiny shiners and "bait minnows" of our rivers and brooks, and those of the Old World, one of which is the smallest fish known; it includes several families of deep-sea fishes, often of quaint form and with curious appendages; here, too, is the valuable blackfish of Alaska, the amphibious, phosphorescent little fish of Indian bays and estuaries which when salted and dried forms the Oriental delicacy called "Bombay duck"; and here are the blind fishes of the Mammoth and other American caves. The Heteromi and Cateosteomi are almost equally miscellaneous assemblages, the most notable members of the latter being the funny little pipefishes and sea horses that lurk in the eelgrass near shore, and the males of which carry the eggs and young about in a pouch on the belly. In the next suborder, Perceosces, we find more strange denizens of the mid-oceanic depths, especially the family Chiasmodontidæ, besides some surface ones of ancient lineage, such as the gar and snakeheads of tropical waters, the flying fish and the mullets. The Anacanthini is a small group containing the remarkable pelagic and abyssal macrurids, the fierce barracudas, and the most valuable single family of food fishes in the whole list—the cods.
The cod family (Gadidæ) has many species in northern seas and a few south of the equator. It includes, besides the cods, the haddock, hake, whiting, coalfish, capelin, ling, and several other market fish of importance. The cod is a deep-water fish which goes about in great schools whose movements are not well understood, but in winter they approach the northern shores of the continent, seeking shallows on which to spawn, and it is then on the "banks," off New England and Newfoundland, that the most profitable fisheries are followed. The cod is extraordinarily prolific, and in addition to this it is propagated artificially more extensively than any other fish.
Thus we come to the last suborder, Acanthopterygii, or "spiny-finned" fishes, in which are classified the greater number of really modern and more or less familiar swimmers in the "briny deep." Among American members are the sunfishes and black bass, the perches and darters; the great family (Serranidæ) of sea bass, snappers and West Indian groupers; the tilefish, which appears and disappears in a puzzling fashion; the grunting drums and their relatives of the Scienidæ; the porgies, sheepshead, and other Sparidæ; the brilliantly colored angel fish of the coral reefs of Bermuda and southward; the surf fishes, so important in California; the wrasses, parrot fish, and globefishes, or boxfishes, that inflate their horny hides when alarmed, until they bob about on the surface like corks.