Aqua•ist, New Yort• Aquarium"A fish eats fish," ts a common slogan. It is the truth and nothing but the truth, but it is not the whole truth. There are many other items on a fish's bill of fare. Numerous examinations of the stomach contents have been made, as you know, by fisheries experts, and observers have set down their findings, so that we are able to say what is the natural food of many species. Aquarium experts and fish eulturists know what substitutes fishes in general will accept in captivity. We even know that there are some foods they would never get in a state of nature, which they prefer to any natural foods you may offer them.We are learning something new every day. Iehthyology still is so young a science that the longer we study fishes, the more deeply we are impressed by our hopeless ignorance of them. We have gathered but the beginnings of knowledge of their migrations, enemies, parasites and diseases, their reproductive and other habits, their natural foods, rate of growth, behavior, emotions, intelligence, and ways of living'. We know just enough about fishes to be able to say with certainty that among no other group of animals is there such marked diversity in structure and form, in size, resistance, breeding habits, schooling and other instincts, and reaction to environment. In the matter of food, perhaps they vary a little less than in other respects, and yet the menu of the order ranges from diatoms to mammals. Diatoms are eaten by the mud-swallowing and plankton-consuming varieties, and others; and the mammals are mostly small ones such as muskrats, though sharks eat seals.
Sometimes we discover accidentally what choice in foods afish may have. At 'the New York Aquarium we exhibit giant groupers--jewfishes. Many grunts and other fishes less than a foot long swim safely in the tank with these monsters. Last year our collecting boat brought in a brown shark two feet long, which was deposited in one of the jewfish tanks. A few minutes later it had disappeared. And so we acquired the knowledge that the jewfish has a weakness for sharks! The question we are asking today is, On what does the food of fishes depend? Is it upon their size, their breeding habits, their schooling instincts and range, the shape of their mouths and teeth, the depth of the water they live in; or 120 Mellen.--Natural and Artificial Foods 121 upon vision, activity, or perchance the whims of individual or specific palate? Let us see, for if we can find this out, we shall know fishes at least a little better.
SIZE.As to size: the smallest of fishes are omnivorous, with a decided preference for animal food, among them the guppy (Lebistes reticult•tus) and top minnow (Heterandria formosa). These have been maintained successfully in home aquaria without the introduction of food, being left to browse upon the filamentous algae that grow on glass and plants.They are fond of small invertebrates, such as water fleas and insect larvae and the minute fry of fishes including their own offspring; but in captivity they greedily accept ...