Popular Science Monthly/Volume 62/November 1902/How to Collect Fishes
|HOW TO COLLECT FISHES.|
By President DAVID STARR JORDAN,
LELAND STANFORD JUNIOR UNIVERSITY.
IN the collection of fishes, three things are vitally necessary a keen eye, some skill in adapting means to ends, and some willingness to take pains in the preservation of material.
In coming into a new district the collector should try to preserve the first specimen of every species he sees. It may not come up again. He should watch carefully for specimens which look just a little different from their fellows, especially for those which are duller, less striking or with lower fins. Many species have remained unnoticed through generations of collectors who have chosen the handsomest or most ornate specimens. In some groups, with striking peculiarities, as the Trunk-fishes and Porcupine-fishes, practically all the species were known to the predecessors of Linnæus. No collector could pass them by. On the other hand, new gobies or blennies can be picked up almost every day in the lesser known parts of the world. For these overlooked forms, herrings, anchovies, sculpins, blennies, gobies, scorpion-fishes, the competent collector should be always on the watch. If any specimen looks different from the rest, take it at once and find out the reason why.
In most regions, the chief dependence of the collector is on the markets, and these should be watched most critically. By paying a little more for unusual, neglected or useless fish, the supply of these will rise to the demand. The word passed along among the people of Onomichi, in Japan, that 'Ebisu the fish-god was in the village' and would pay more for Okose (poison Scorpion-fishes) and Umiuma (Seahorses) than real fishes were worth soon brought (in 1900) all sorts of Okose and Umiuma into the market when they were formerly left neglected on the beach. Thus with a little ingenuity the markets in any country can be greatly extended.
The collector can, if he thinks best, use all kinds of fishing tackle for himself, hooks, flies, bait, seines, traps, anything that will catch fishes. In Japan he can use the 'dabonawa' long lines, and secure the fishes which were otherwise dredged by the Challenger and Albatross. If dredges or trawls are at his hand he can hire them and use them for scientific purposes. He should neglect no kind of bottom, no conditions of fish life which he can reach. Especially important is the fauna of the tide-pools, neglected by almost all collectors. As the tide goes down, especially on rocky capes which project into the sea, myriads of little fishes will remain in the rock-pools, the algæ and the clefts of rock. In regions like California, where the rocks are buried with kelp, blennies will lie in the kelp as quiescent as the branches of the algæ themselves until the flow of water returns.
A sharp, three-tined fork will help in spearing them. The water in pools can be poisoned on the coast of Mexico, with the milky juice of the 'Hava' tree, a tree which yields strychnine. In default of this, pools can be poisoned by chloride of lime, sulphate of copper, or, if small enough, by formaline. Of these, a solution of commercial chloride of lime, yielding free chlorine gas is cheapest and most serviceable. By such means the contents of the pool can be secured and the next tide carries away the poison. The water in pools can be bailed out, or better emptied by a siphon made of small garden hose or rubber tubing. On rocky shores and about coral reefs dynamite can be used to very great advantage, if the collector or his assistant dare risk it, and if the laws of the country do not prevent. Most effective in rockpool work is the help of the small boy. In all lands the collector will do well to take him into his pay and confidence. Of the hundred or more new species of rock-pool fishes lately secured by the writer in Japan, fully two thirds were obtained by the Japanese boys. Equally effective is the 'muchacho' on the coasts of Mexico.
Masses of coral, sponges, tunicates and other porous or hollow organisms often contain small fishes and should be carefully examined. On the coral reefs the breaking up of large masses is often most remunerative. The importance of securing the young of pelagic fishes cannot be too strongly emphasized.
Fishes must be permanently preserved in alcohol. Dried skins are far from satisfactory, except as a choice of difficulties in the case of large species. Dr. Gunther thus describes the process of skinning fishes:
The scales of some fishes, as for instance of many kinds of herrings, are so delicate and deciduous that the mere handling causes them to rub off easily. Such fishes may be covered with thin paper (tissue paper is the best) which is allowed to dry on them before skinning. There is no need for removing the paper before the specimen has reached its destination.
Scaleless fishes, as siluroids and sturgeons, are skinned in the same manner, but the skin can be rolled up over the head; such skins can also be preserved in spirits, in which case the traveller may save himself the trouble of cleaning the head.
In the field it is much better to use formalin (formaldehyde) in preference to alcohol. This is an antiseptic fluid dissolved in water, and it at once arrests decay, leaving the specimen as though preserved in water. If left too long in formalin fishes swell, the bones are softened and the specimens become brittle or even worthless. But for ordinary purposes (except use as skeleton) no harm arises from two or three months' saturation in formalin. The commercial formalin can be mixed with about 20 parts of water. On the whole it is better to have the solution too weak rather than too strong. Too much formalin makes the specimens stiff, swollen and intractable, besides too soon destroying the color. Formalin, has the advantage, in collecting, of cheapness and of ease in transportation, as a single small bottle will make a large amount of the fluid. The specimens also require much less attention. An incision should be made in the right side of the abdomen to let in the fluid. The specimen can then be placed in formalin. When saturated, in the course of the day, it can be wrapped in a cloth, packed in an empty petroleum can and at once shipped. The wide use of petroleum in all parts of the world is a great boon to the naturalist. Before preservation, the fishes should be washed, to remove slime and dirt. They should have an incision to let the fluid into the body cavity and an injection with a syringe is a useful help to saturation, especially with large fishes. Even decaying fishes can be saved with formalin.
The collector should mark localities most carefully, with tin-tags and notebook records, if possible. He should, so far as possible, keep records of life colors, and water color sketches are of great assistance in this matter. In spirits or formalin, the life colors soon fade, although the pattern of marking is usually preserved or at least indicated. A mixture of formalin and alcohol is favorable to the preservation of markings. In the museum all specimens should be removed at once from formalin to alcohol. No substitute for alcohol as a permanent preservative has been found. The spirits derived from wine, grain, or sugar is much preferable to the poisonous methyl or wood-alcohol.
In placing specimens directly in alcohol, care should be taken not to crowd them too much. The fish yields water which dilutes the spirit. For the same reason, spirits too dilute are ineffective. On the other hand, delicates fishes put into very strong alcohol are likely to shrivel, a condition which may prevent an accurate study of their fins or other structures. It is usually necessary to change a fish from the first alcohol used as a bath into stronger alcohol in the course of a few days, the time depending on the closeness with which fishes are packed. In the tropics, fishes in alcohol often require attention within a few hours. In formalin, there is much less difficulty with tropical fishes.
Fishes intended for skeletons should never be placed in formalin. A softening of the bones which prevents future exact studies of the bones is sure to take place. Generally alcohol or other spirits, arrack, brandy, cognac, rum, sake, 'vino' can be tested with a match. If sufficiently concentrated to be ignited, they can be safely used for preservation of fishes. The best test is that of the hydrometer. Spirits for permanent use should show on the hydrometer 40 to 60 above proof. Decaying specimens show it by color and smell, and the collector should be alive to their condition. One rotting fish may endanger many others. With alcohol it is necessary to take especial pains to ensure immediate saturation. Deep cuts should be made into the muscles of large fishes as well as into the body cavity. Sometimes a small distilling apparatus is useful to redistil impure or dilute alcohol. The use of formalin avoids this necessity. Small fishes should not be packed with large ones; small bottles are very desirable for their preservation. All spinous or scaly fishes should be so wrapped in cotton muslin as to prevent all friction.
The methods of treating individual groups of fishes and of handling them under different climate and other conditions are matters to be learned by experience. Eternal vigilance is the price of a good collection as it is said to be of some other good things. Mechanical collecting, picking up the thing got without effort and putting it in alcohol without further thought, rarely serves any useful end in science. The best collectors are usually the best naturalists. The collections made by the men who are to study them and who are competent to do so are the ones which most help the progress of ichthyology. The student of a group of fishes misses half the collection teaches if he has made no part of it himself.