Popular Science Monthly/Volume 32/April 1888/The Family-Life of Fishes
| THE FAMILY-LIFE OF FISHES. |
By KARL HENNINGS.
AMONG the nest-building fishes which inhabit German waters, the most interesting is the tiny "stickleback," whose life-history has been carefully studied. The home of this little animal is some-times found in ditches, hanging among branches and twigs of plants; the nest is about the size of the average hand, and in structure and material bears a marked resemblance to the round nest of the tit-mouse. It is a peculiar and remarkable fact that among the sticklebacks the hatching is done by the male and not by the female fish. The building of the nest, a task to which the male also attends, is an interesting event. For many days in succession the little animal, whose energy and perseverance are truly worthy of admiration, collects its material, which consists of loose stalks, plant-shreds, root-fibers, and grass. These it assorts carefully, discarding all material that proves too light. It often drags along pieces exceeding its body in length, and sometimes with great exertion strips growing plants. All this material is worked up into a tangled mass, and layers of sand are scattered in between. The nest is rendered firm by a glue-like juice, which the little mason excretes after the completion of each layer, gliding slowly over the structure; this causes the separate parts of the nest to adhere closely together. The whole, when completed, has the appearance of a sand-hill, and is detected with much difficulty. While at work the fish rarely partakes of any food; it seems that during this blissful period of its existence it finds no pleasure in such everyday events; but with intense animosity it drives back any jealous rivals, larvae, salamanders, or water-bugs, which cross its path, sometimes with evil sometimes with harmless intentions. After the troublesome hatching-time is over, the anxious papa still continues to care for his numerous offspring; by day and by night he watches over them, and drives away all creatures whose approach seems dangerous. This unremitting watchfulness ceases only when his young are able to raise their weapons of defense and have become somewhat acquainted with their surroundings. Any inquisitive little one venturing too far away is quickly sent home, and it actually happens that those who are very disobedient are imprisoned in the nest. The home-life of these little animals really presents an abundance of interesting and touching traits.
To study the family of fishes which inhabit the ocean and sea-gulfs is naturally more difficult, and rarely proves as successful as observation extended to the inhabitants of our fresh-water lakes, rivers, and streams; but, by the co-operation of naturalists, fishermen, and sailors, many events happening in the deep seas have been observed that afford a further insight into the life and the habits of fishes. In former times fishes were considered mute, impassive, and possessed of but little intelligence; nowadays we know that in these respects they can claim to rank as equals with many inhabitants of terra firma. A case in view is the Cyclopterus lumpus. This fish shows a decided attachment to its young, and is often seen with numerous little ones, of which it takes the best possible care. It is found chiefly near England's
Fig. 1.—Cyclopterus lumpus. the Lumpfish, with its Young.
shores, and along the coast of Maine in America. The Cyclopterus has a peculiar form; its body displays many spots, swellings, and lumps which are partially arranged in regular order. It is, generally speaking, not a dangerous creature, never doing harm to any of its fellow-fish. It is defenseless and harmless, and on account of its unwieldy shape moves awkwardly and comparatively slowly. The only weapon this animal really possesses is its extreme ugliness, its uncouth form, which frightens its enemies and not infrequently scares them away. The young of the Cyclopterus follow their mother as little chicks are wont to follow a hen; they play and frolic about her, and are as obedient as little chicks are to the call of their mother. In case any strange object drifts nigh, or an enemy approaches, the whole company, consisting often of several hundred little beings, crowd closely up to their protector. As already said, the Cyclopterus is but a poor swimmer, and it seems but natural to suppose that large waves should threaten danger, and that heavy breakers could easily hurl it on shore. But kind Nature has taken precautions. This curious inhabitant of the sea is capable of adhering so firmly to any object, rocks, drift-wood, or marine plants, that the most powerful waves can not tear it from its support. Its numerous slimy fins can be made to serve as a suction apparatus, so that its body, when thus fastened to a stone, appears like a ship riding at anchor. The Cyclopterus attains a length of about sixty centimetres, and varies in weight from three to four kilogrammes, sometimes even attaining a weight of six to seven kilogrammes. It can change its color from a yellow or a gray to black. Its progeny is remarkably numerous. Sometimes it is found in the Baltic Sea, but is seldom caught, on account of its peculiar mode of living. The adhesion of its body to the objects to which it has become fastened is so firm that a force of thirty-six kilogrammes is required to tear from its hold a Cyclopterus of about twenty centimetres in length. It has also been observed that this fish remains in one and the same place for weeks together, waiting until its food, which consists of sea-nettles and the smallest of fish, has come within convenient reach. Similar to the stickleback, the Cyclopterus faithfully guards its eggs, which always number hundreds of thousands, and proves very courageous in attacking dangerous enemies and heroically shielding its young. The male fish covers the eggs with his body, and retains this position until the little ones have made their appearance. These fishes are seldom taken by man; in Greenland and Iceland they are sometimes caught in nets, and when found among sea-plants they are speared with a prong-shaped iron. Their worst enemy is the seal, who seems to find them palatable food, although they must be skinned before they can be eaten.
Some species of Ophiocephalus present interesting features in their home-life. One variety which inhabits the Sea of Galilee, in Palestine, is known to seek shallow water during breeding-time. The parent fishes fasten small pieces of grass, leaves, sea-weeds, parts of shells, and small particles of wood, to a rock, or to the roots of an old tree, and weave the whole mass into an oval-shaped nest for their young; they arrange the stalks of grass so as to form a net-like cover, and then fill in the interstices with mud, taking care, however, to leave several openings. At the lower end they place an attachment, generally egg- or pear-shaped, which serves as a sort of cradle, being rocked to and fro by the swell of the waters. The eggs are deposited in the center, and stick to the grass and side-walls of the structure. After the lapse of but a short space of time the nest becomes crowded with tiny beings, which seem anxious to be set at liberty, but are carefully guarded by father and mother until they are capable of taking care of themselves and facing the vicissitudes of life. Mutual attachment among the different members belonging to a family of this species seems to be a marked trait; it has often been observed that they protect their young by harboring them in their mouth whenever danger threatens. Even among the larger salt-water fishes, this manner of sheltering the brood is occasionally adopted. As an example may be cited a fish which the Chinese call lau-lau. It attains a length of
Fig. 2.—The Ophiocephalus and its Brood.
thirteen feet and weighs over two hundred pounds. The same observation has been made with fishes whose home is in the lagoons of South America. The young fishes seem so accustomed to this place of refuge that, on perceiving any commotion in the water that seems in the least suspicious, they hasten en masse into the protecting mouth of their mother. Another fish, living near the coasts of South America, is known to fasten its young ones to its fins and body by means of a glue-like substance. This gives to these fishes the appearance of being covered with small protuberances.
On the coast of Guiana fishes have been found which dig their nests in miry shores, and live there much as sand-swallows do on land.
Another variety of the above-mentioned Ophiocephalus, a native of India, also makes its home in holes in the ground, and can remain in its nest for some time, even after the water has receded. These generally live together in couples. If the earth becomes too dry, they leave their houses and creep along for quite a distance on the damp ground. The lower classes of natives, whenever they see them engaged in such pilgrimages, believe them to have fallen from the sky. Indian jugglers often keep these fishes in order to let them crawl about on land, and have the people enjoy the wonderful spectacle. Another fish, living in the Gulf of Panama, resembles the kangaroo, inasmuch as it possesses a bag-like receptacle in which it bears its eggs.
The most peculiar, however, of all fishes is the sea-horse (Hippocampus), 
Fig. 3.—The Hippocampus and its Family. remarkable on account of its queer shape as well as on account of its strange homestead and habits of life. With their numerous joints and their circular tail, these fishes have more the appearance of a plant than of an animal. While swimming they keep in an upright position, holding their tail in readiness for the peculiar use to which they put it. Very quickly they coil it around sea-weeds, and then carefully watch the surrounding water, on the lookout for booty, which, when perceived, they pursue with great dispatch. It sometimes happens that, when two of these fishes meet, they encircle each other with their tails, and they often have a hard time of it before they can again separate. By the peculiar growth of a part of the epidermis on the sea-horse a perfect pocket is formed, in which their eggs are allowed to develop.
Yet another kind of fish possesses a form still more weird, and may, on account of its shape and color, be easily mistaken for floating sea-weeds. And in this peculiar resemblance lies its greatest safeguard. In like manner the sea-needle greatly resembles the sea-plants among which it lives, not only in form, but also in color, which it can easily change from a gray or brown to a bluish or greenish hue.—Translated for the Popular Science Monthly from Daheim.