CHAPTER V.. Surface-Swimming Fauna (vertebrates).

SURFACE-SWIMMING FAUNA (VERTEBRATES).

In the preceding chapter we have considered only those animals of the surface of the sea, which, owing either to their small size or the transparency of their bodies, are not as a rule conspicuous to a passenger on board a mail-steamer. Such a passenger might cross the ocean many times without realising in the least the wealth of animal life that there is in every wave that breaks upon the ship, and yet be impressed with what he has seen of the Whales and Porpoises, the Sharks, Bonitos and Flying-fish.

It is to these groups of animals that a few lines must be devoted before closing our story of the surface-swimming Fauna. If the young and immature stages be for the moment left out of consideration, it may be said that nearly all the Fish and all the Whales and Porpoises are large, opaque in appearance, and perfectly conspicuous. Moreover, they are all strong and rapid swimmers, capable of roaming over wide areas of the sea in search of prey, and independent of, except in so far as their prey are influenced by, the currents and winds. It is clear that they cannot be said to ‘float’ and ‘drift’ about in the ocean, and consequently they do not strictly belong to the Plankton. The term used in speaking of them collectively is the Nekton, which means the swimming population.

The greatest number of the Fish of the sea are shore Fish; that is to say, they habitually feed at, or close to, the bottom of the shallow waters near the coasts or sunken banks.

But there is a very considerable number that are strictly pelagic, living and feeding far away from the shores, bringing forth their young alive, or shedding floating eggs, and in every way independent of the shore and of the bottom.

It is difficult to give any general features by which they are characterised, as so much variety may be observed among them; but as a general rule they are elongated in form, round or oval in section, in colour green or gray above, with silvery white bellies. Some of these, such as the Flying-fish and the Flying-gurnard, are capable of making very considerable flights in the air, their pectoral fins being enormously elongated, and when fully expanded somewhat similar to the wing of an Insect.

The Flying-fish occur in shoals in nearly all tropical and subtropical seas. When disturbed by a ship on a calm day it is said that they spring out of the sea, expand their fins, describe a regular parabolic curve in the air, and then fall with a splash into the water. There is a considerable controversy raging on the question of the use of their fins in this flight through the air, some observers believing that the fins are used only as a kind of parachute, and others that they are used like wings for raising the body above the water. It is very difficult to decide which view is correct.

In the Indian Ocean I watched the Flying-fish for several days during rather rough weather, and my impression was most distinctly that in the middle of the flight the fins are vigorously flapped four or five times, the flapping being followed by a decided rise in the air. On the other hand, it may be that this flapping appearance is caused by the wind catching the wings in a certain position, and not by the muscles of the fish. Whether the flying is actually assisted by the flapping of the wings or not, it is certain that the Fish do rise in gusty weather to a very considerable height, frequently falling on to the decks of steamers twenty feet above the water line.

At night, these Fish fly at the ships and not away from them, as they do in the day-time, and the natives in some parts of the Malay Archipelago catch them in large numbers by holding up a torch by the side of a large sheet, when the Fish flying at the bright light and striking against it, fall into the bottom of the canoe. Flying-fish are excellent to eat, their flesh being similar in taste to that of the Herring, but an epicure would probably say that it is not quite so good.

The Bonito is a fish occurring over a wide area of the tropical and temperate seas, which sometimes makes tremendous jumps out of the water. I have seen it frequently on the coast of Celebes jump to a height which I roughly estimated as at least fifteen feet. It is said to feed upon the Flying-fish, and it is probable that it has acquired the power of springing out of the water in the pursuit of its prey.

The pelagic Fish, which has acquired the widest reputation, and that an evil one, is the “blue-Shark.” This occurs in the tropical and occasionally in temperate seas. Its usual size is from twelve to fifteen feet, but, according to Dr Günther, individuals of twenty-five and more feet are occasionally captured. It is extremely voracious, attacking anything of a fleshy nature that it observes in the water.

One of the most remarkable animals of the open ocean is the Sun-fish. It has a very wide distribution in the tropical and temperate regions. In the adult condition it is almost circular in outline and considerably flattened from side to side like a John Dory. It sometimes reaches a size of eight feet in diameter and a very great weight. From the little that is known of its development it apparently undergoes some extraordinary changes in shape before it reaches the adult form.

In addition to these and several other Fish of a large size which may be found at the surface of the open ocean, there are several species known to science which never grow to a length of more than a few inches. Many of these are characterised by remarkably long fin rays, by their large eyes, or by other features which may be regarded as special modifications for their peculiar habits.

A very interesting genus is Scopelus, which is found very widely distributed in tropical and other seas. Some of the species live in very deep water, and are purely abysmal in habit, but most of them rise to the surface at night, when they may be caught in immense numbers. In form they are not unlike a small Sprat, but they exhibit on each side of the body a series of minute eye-like organs, which emit a phosphorescent light.

In addition to these Fish which are found far out in the open ocean, there are several genera, which form an important feature of the surface waters in the neighbourhood of the coasts. Among them we find such valuable food-fish as the Herrings, Sprats, Mackerels, and Pilchards.

The complete history of the Herring has yet to be written, for, notwithstanding the laborious investigations of several naturalists, working independently, or as officers of the Marine Biological Association and similar Institutions, there are some facts and stages which have, up to the present time, escaped observation.

The Herring species is divided into a number of races, which, differing from one another only slightly in anatomical characters, have different seasons for depositing their eggs. This fact has only recently been thoroughly established; and while it assists us greatly in the task of completing the history of the Fish, it definitely destroys the validity of many theories which were prevalent among fishermen and others before the days of the more exact scientific treatment of fishery questions.

It is well-known that from the end of the month of June to December immense shoals of Herrings are found in the North Sea. It is quite impossible to estimate the numbers of Fish in these shoals, but they are so great that if they could be counted it would probably be found that the Fish that are annually caught by all the fishing boats, form but an insignificant fraction of the whole. All of these Fish are in such a condition that it is evident their spawning time is close at hand. When they are ready they approach the coasts, the exact time varying according to the race of Herrings, and the spawn is deposited on or close to the ground, the eggs becoming attached to stones and other objects on the bottom. After the Herrings have spawned, they seem to disperse, or, at any rate, to disappear from the surface waters of the North Sea. What actually becomes of these shoals of spent Herrings is not known, but it is a fact that in the spring there are so few Herrings to be found in the narrower part of the North Sea that it does not pay the fishing boats to go after them. It is possible, however, that, after the spawning process, the Herrings migrate to the deeper water of the Norwegian coasts, in order to feed on the Crustaceans and other forms of life that are to be found there in abundance.

The Mackerel do not apparently make such extensive migrations as the Herrings. They spawn in the open sea, five or ten miles from the coast, during the spring time. The egg of the Mackerel, unlike that of the Herring, does not sink to the bottom when it is spawned, but, being provided with a large oil globule, it is light enough to remain on the surface until the young larva is hatched. After the spawning has taken place the Mackerel approach the coast, and will even enter bays and narrow inlets on the shores in pursuit of the young Sprats and other small Fish upon which they prey.

A great deal could be written on the history of the Pilchards, the Anchovies, the Sprats, and other Fish which frequent the surface waters of the sea in the neighbourhood of the European coasts. No two species seem to have precisely the same habits, and what is known about them presents us with many curious and remarkably interesting facts. For further details, however, I must refer the reader to the larger and more comprehensive books dealing specially with the subject, for space must still be found for a few words on another group of animals which play a conspicuous part in the story of life in the seas.

The animals composing the class of Mammals are distinguished from other Vertebrates by the fact that the females are capable of providing milk for their young ones after birth. Most of the Mammals are strictly terrestrial, but three orders, namely, the Cetacea, the Sirenia, and the Carnivora contribute to the surface-swimming population of the sea.

The Cetacea are all aquatic. The order includes the many genera of Whales, Porpoises and Dolphins.

The Right-whales are distinguished by the enormous size of the mouth and the absence of the little triangular fin in the middle of the back which is found in the other Whales.

These animals have no teeth in the adult condition, but are provided with a series of plates situated at the sides of the mouth which are used as strainers to catch the small Pteropods and other animals living in the water which pass through the great gape. The plates are composed of a substance called “Baleen,”--the well-known whale-bone of commerce,--they are triangular in shape, and frayed out into a brush-like edge on the side that faces the cavity of the mouth. The Greenland Right-whale attains to a size of fifty feet in length when fully grown, and it is usually found in shoals among the ice floes of the far north.

In former times many Right-whales belonging to species allied to the Arctic form occurred in the temperate regions of the Atlantic and Pacific Oceans, but in consequence of the valuable fishery they afforded they are now becoming very scarce.

The largest of all the Whales--in fact, the largest existing animal--is the Blue-whale, which attains to the enormous length of 86 feet. It spends the winter in the open seas, and approaches the coast of Norway in the spring.

The Whales, like all the animals of the Class to which they belong, are air-breathers. They are able, however, to hold their breath for a considerable time under water. When they come to the surface to renew the air-supply in their lungs, they first make a violent expiratory effort from the nostril, and drive a column of spray many feet into the air above them. This phenomenon is called by the whale fishers “spouting,” and it was erroneously supposed by them to be a column of water forced from the mouth into the nostril, and then expelled at the surface.

The Dolphins and the Porpoises are distinguished from the true Whales by the fact that they are provided with teeth, on one or both of their jaws, and there is no “whale-bone.”

The Sperm-whale has probably been called a “Whale” from its enormous size, but it is anatomically very widely separated from the true whales and more closely allied to the Dolphins. It has no “whale-bone,” and the lower jaw is provided with a row of sharp-pointed teeth set in a groove in the bone. Its great value is due to the fact that there is a large cavity situated above the skull, containing an oily substance from which “Spermaceti” is made.

The principal food of these large “Toothed-whales” seems to be Cuttlefishes, and the examination of the contents of their stomachs, which has been carried out on board the Prince of Monaco’s private steam-ship when engaged on a scientific cruise, has yielded some new forms of these giant Molluscs. The Sperm-whales, however, do not disdain a Fish diet as well.

The Porpoises are found on our own coasts. They may often be seen following the “schools” of Whales as they approach the coast in the summer months, and they occasionally chase their prey some distance up the estuaries of the English rivers. The habit that Porpoises have of accompanying ships for long distances affords us many opportunities of watching their graceful movements, and of estimating the very great speed with which they can swim through the water for hours at a stretch. It is difficult to understand the meaning of this habit of following ships. It has been suggested that the Porpoises mistake the ship for a huge Sperm-whale, and hope to benefit by stray morsels of large fish that fall from its jaws. But this theory does not account for the fact that the Porpoises so often go in front of the ship. The following extract from Darwin’s “Voyage of the Beagle” gives, in a few words, a vivid picture of Porpoise life:--

“In our passage to the Plata, we saw nothing in particular, excepting on one day a great shoal of Porpoises, many hundreds in number. The whole sea was in places furrowed by them; and a most extraordinary spectacle was presented, as hundreds, proceeding together by jumps, in which their whole bodies were exposed, thus cut the water. When the ship was running nine knots an hour, these animals could cross and recross the bows with the greatest ease, and then dash away right ahead.” This description reminds me very forcibly of a sight I once saw in the Talaut Islands, south of the Philippines. In passing between two of the islands the strait seemed to be alive with Porpoises tearing through the water at a terrific pace. They accompanied the steamer for about six hours and then suddenly disappeared. My impression was that they were attracted to the ship not from a desire for more food, for there was an abundance of Herrings in the straits at the time, but from sheer curiosity. I think the feeling of curiosity, that is to say, the desire to go and look at something strange or unusual, is much more prevalent among animals than we generally suspect.

It is an interesting fact about the Porpoise that, although it is so fish-like in shape, it should present some features which remind us of the Pig. The English word is probably derived from the two French words porc and poisson, and therefore means “Pig-fish.” The Germans call it Meeresschwein, meaning “Sea-pig,” and the Malay word for it is “Babi-laut,” which also means “Sea-pig.” But if we make some allowance for those who call these Cetaceans “Pigs,” we must make none for those who call them “Fish.”

Like all the other members of their order the Porpoises have a fish-like tail, but the flaps are placed horizontally and not vertically as they are in Fish. The skin is quite naked, having no scales of any kind, and there are no gills or gill-openings. Like all other Mammals the Cetaceans bring forth their young alive, suckle them, and breathe air by means of lungs. But there can be no doubt that they are extremely modified for their aquatic life. The characteristic covering of Mammals--the hairs--is, in the adult condition of the Whales, entirely wanting, and is represented in other members of the Class by only a few bristles on the snout. The heat of the body is maintained by a thick coat of fat, called the blubber, lying immediately beneath the skin, and this yields, on boiling, a valuable oil, which helps to support the whale-fishermen. One of the most striking modifications, however, is the loss of the hind limbs. It is only in some species that even rudiments of these have been found. All of these facts indicate that the Cetaceans must have taken to a mode of life in the water a very long time ago, and the study of the rocks proves the existence of Whales as far back as Eocene times, but it is of interest to note that, in some respects, the oldest fossil Cetaceans are less specialised than those that are now living.

The class of Mammals called the Carnivora includes the Cats, Dogs, Ferrets and many other animals which are purely terrestrial, but one of its divisions is entirely composed of those well-known aquatic animals the Seals and the Walrus. If we take the common Seal as an example of this group, and compare it with the Porpoise, as a representative of the Cetaceans, we find that in habits as well as in anatomy the former is less completely changed than the latter. The Seal frequently comes to land to bask in the sun, or to produce and care for its young, and it is capable of making some progress over the rocks by the help of its flipper-like fore-limbs; the Porpoise, on the other hand, never leaves the water of its own free will. Unlike the Porpoise the body of the Seal is covered with a thick coat of hairs, and the hind limbs are retained. Although there is a general resemblance in the form of the body between these two animals--this form being, in all probability, mechanically the best for rapid progress through the water--a glance at their skeletons shows great and important differences, which the merest tyro in anatomy could point out. In expression, too, there is a marked difference, for while the Porpoise has a certain cast of countenance which, when seen at a distance, deserves the epithet “pig-faced,” the face of the Seal, with its large round eyes, its small nose and high intelligent brow, is almost human in expression.

The Seal has a habit of raising its head above the water and staring at an approaching boat, and when doing this it may readily be mistaken at first sight for a man overboard, but no one could ever mistake a Porpoise for a human being.

The common Seal has a very wide range occurring near the coast of both the Atlantic and Pacific Oceans. It is found on some of the more sequestered parts of the British shores, but not in large numbers, for the common Seal, unlike many of its allies, does not appear to congregate in large shoals at any time of the year. They are described as being timid, inoffensive creatures, easily tamed, passionately fond of their children and taking an intelligent interest in music.

There are several animals closely related to the Seal, occurring in different parts of the world; and a few words may be said about the remarkable animal called the “Sea-elephant,” which is found on Kerguelen island in the Antarctic Ocean. The popular name was given to the animal in consequence of the fleshy protuberant nose which has been compared with the trunk of an Elephant and is possessed only by the male. The late Professor Moseley, who came across a small herd of them when the Challenger was at Kerguelen, says: “The trunk is produced by an inflation of a loose tubular sac of skin placed above the nostrils, just as is the ‘Cap’ in the northern Bladder-nose Seal. The trunk is evidently, as appears from both the drawings, sacculated, and hence irregular in form when inflated.”

The Sea-lions and Sea-bears or the Eared Seals, as they are sometimes called, form a very distinct family. The one that is best known to the general public is the Californian Sea-lion, as it often lives in captivity in the European menageries for many years and attracts the attention of the visitors by the tricks which it is taught to perform.

In the spring months of the year these creatures may be seen in great numbers on the rocky islands off the coast of California, where they come to breed.

The most important of them all, from a commercial point of view, is the Fur-seal from the Northern Pacific. In the month of May these animals approach the Prybilov islands in the East, or the Commander islands in the West of the Behring Sea. The first to arrive on the land are the old males. These choose for themselves certain areas or ‘homes’ on the shore and fight desperately for their possession with all who dare to come within their reach. When matters are at length somewhat settled the time arrives for the females to approach the shore. The fighting then begins again with renewed vigour, and desperate encounters take place for the possession of a goodly stock of wives for the season.

There seems to be little in the way of courtship in the domestic economy of the Fur-seals, the wives being simply “captured” by the scruff of their necks when they come within reach of a would be husband, and retained in his harem just so long as he can prevent any one of his neighbours from stealing her. The Fur-seal, like all his relations, is polygamous, but the number of wives that each male appropriates to himself seems to vary very considerably. Mr Elliott mentions a case in which there were as many as forty-five females in one home, but, as a general rule, the number is much less. As there is only one male to every twelve or thirteen females, there are numerous males over, which cannot found a home for themselves. These bachelors, together with a number of the young females, resort to a separate piece of ground, where they spend their time in playing games. The play-grounds are however the scene of the tragedies of Seal life, for they are resorted to by the hunters, who slaughter immense numbers of the larger males for the sake of their valuable skins. As the skins of the old male Seals are not of very much value and as it is important, for the perpetuation of the race, to preserve the females from injury, the breeding grounds are usually not molested. It is therefore the bachelor seal of from two to five or six years of age that has to supply the market. Those naturalists who have visited the Seal rookeries on these islands say that the numbers of these animals that can be seen at one time is almost incredible. We can form some estimate of them when we learn that over a hundred thousand skins are exported from the Prybilov islands alone every year.

The Seals leave the rookeries in the month of August, and after swimming about for some time in the neighbourhood of the islands, eventually depart into the open ocean in search of the food their famished bodies need so much after the fasting and fighting of the breeding months.

The largest of all these aquatic Carnivores is the Walrus, which lives within a short distance of the shores of the lands in the Arctic regions. It is easily distinguished from the Seals by its great size, the males reaching a length of 10 or 12 feet, and by the enormous canine teeth in the upper jaws, which project downwards from the cover of the lips in the form of two large pointed tusks. These tusks are used for hoisting the bodies of the animals on to the ice, for digging in the sand in search of the Mussels upon which they feed, and for general fighting purposes.

It is said that in former times the Walruses lived in immense herds in regions much further south than they do now; but the ravages of the hunter, who chased them for their ivory tusks and their oil, have driven them into regions where they are rarely visited by anyone but the Arctic explorer; and to those of my readers who wish to learn more of their habits, I can but say that in the pages of Dr Nansen’s book, “Farthest North,” he will find the story of the Walrus written in a manner which no man living could have done more vividly and brilliantly than the great Norwegian zoologist and explorer.