An introduction to the study of fishes

by Albert C. L. G. Günther

Skeletons of large osseous fishes are as valuable as their skins. To preserve them it is only necessary to remove the soft parts of the abdominal cavity and the larger masses of muscle, the bones being left in their natural continuity. The remaining flesh is allowed to dry on the bones, and can be removed by proper maceration at home. The fins ought to be as carefully attended to as in a skin, and of scaly fishes so much of the external skin ought to be preserved as is necessary for the determination of the species, as otherwise it is generally impossible to determine more than the genus.

A few remarks may be added as regards those Faunæ, which promise most results to the explorer, with some hints as to desirable information on the life and economic value of fishes.

It is surprising to find how small the number is of the freshwater faunæ which may be regarded as well explored; the rivers of Central Europe, the Lower Nile, the lower and middle course of the Ganges, and the lower part of the Amazons are almost the only fresh waters in which collections made without discrimination would not reward the naturalist. The oceanic areas are much better known; yet almost everywhere novel forms can be discovered and new observations made. Most promising and partly quite unknown are the following districts:—the Arctic Ocean, all coasts south of 38° lat. S., the Cape of Good Hope, the Persian Gulf, the coasts of Australia (with the exception of Tasmania, New South Wales, and New Zealand), many of the little-visited groups of Pacific islands, the coasts of north-eastern Asia north of 35° lat. N., and the western coasts of North and South America.

No opportunity should be lost to obtain pelagic forms, especially the young larva-like stages of development abounding on the surface of the open ocean. They can be obtained without difficulty by means of a small narrow meshed net dragged behind the ship. The sac of the net is about 3 feet deep, and fastened to a strong brass-ring 2 or 2½ feet in diameter. The net is suspended by three lines passing into the strong main line. It can only be used when the vessel moves very slowly, its speed not exceeding three knots an hour, or when a current passes the ship whilst at anchor. To keep the net in a vertical position the ring can be weighted at one point of its circumference; and by using heavier weights two or three drag-nets can be used simultaneously at different depths. This kind of fishing should be tried at night as well as day, as many fishes come to the surface only after sunset. The net must not be left long in the water, from 5 to 20 minutes only, as delicate objects would be sure to be destroyed by the force of the water passing through the meshes.

Objects found floating on the surface, as wood, baskets, seaweed, etc., deserve the attention of the travellers, as they are generally surrounded by small fishes or other marine animals.

It is of the greatest importance to note the longitude and latitude at which the objects were collected in the open ocean.

Fishing in great depths by means of the dredge, can be practised only from vessels specially fitted out for the purpose; and the success which attended the “Challenger,” and North American Deep-sea explorations, has developed Deep-sea fishing into such a speciality that the requisite information can be gathered better by consulting the reports of those expeditions than from a general account, such as could be given in the present work.

Fishes offer an extraordinary variety with regard to their habits, growth, etc., so that it is impossible to enumerate in detail the points of interest to which the travellers should pay particular attention. However, the following hints may be useful.

Above all, detailed accounts are desirable of all fishes forming important articles of trade, or capable of becoming more generally useful than they are at present. Therefore, deserving of special attention are the Sturgeons, Gadoids, Thyrsites and Chilodactylus, Salmonoids, Clupeoids. Wherever these fishes are found in sufficient abundance, new sources may be opened to trade.

Exact observations should be made on the fishes the flesh of which is poisonous either constantly or at certain times and certain localities; the cause of the poisonous qualities as well as the nature of the poison should be ascertained. Likewise the poison of fishes provided with special poison-organs requires to be experimentally examined, especially with regard to its effects on other fishes and animals generally.