Making a wide, though general, survey of what game-fish consume as food, it is certain the varied members of the trout, bass, and pike families subsist almost entirely on a fish diet, principally on the large family of minnows, the young of their own kind, and other species of fish. Were it possible that every species of these three game-fish families could be restrained from cannibalism, they would soon multiply so rapidly as to glut the waters in which they abide and utterly destroy all fish life that nature provides as food for them. Cannibalism induces that trait we call "gamy" by necessitating a lifelong battle of existence, both among their own and other species. In the restricted space of a pond or lake, bullheads increase so rapidly that they soon devour every vestige of food where they abide, and then at once proceed to devour each other. This same condition prevails with the muskellunge, pike, and pickerel families. If a plentiful supply of fish food is not available, the bass and trout families also feed on the very young of their own kind. It is claimed by some that the brook-trout is an exception, but I have had several proofs that, after it attains a weight of over two pounds, it makes no distinction between the young of its own kind and the young of perch or sucker. We find this cannibalistic trait even among some species of minnows where the adult fish measures no more than two inches long. Thus it is, from the minnow to the salmon, fresh-water fishes prey unceasingly upon each other just as salt-water fishes do in the ocean.
In a document * issued by the bureau of fisheries, several facts are given that may be of interest to anglers on the various species of minnows useful in destroying the eggs and larvae of mosquitoes in the stagnant water where they breed. Of the large variety of minnows there are four of more than ordinary value as game-fish food: The family of top-minnows, which take their food mostly at the surface of sluggish ponds, creeks, canals, and slow-running rivers. The mud-minnows are bottom feeders, though at times they rise to the surface snapping at low-flying insects. The family of sunfishes are the most abundant, having a wide range from Canada to the Gulf. The family of silversides are the most delicate species of all minnows, being most attractive in appearance for use as bait, but very difficult to transport from their habitat.
* No. 857.
From the scant information I have gathered, it seems that the minnow family has been much neglected by scientific writers, fish culturists and others. Each State should include the breeding and planting of these most valuable fish, not only as food, but for their value as eradicators of mosquitoes, which makes them of the greatest economic importance where mosquitoes are a pest. If it be not feasible for State hatcheries to propagate minnows, nearly all of the different families are easily transported from their natural breeding places in ponds, reservoirs, lakes, rivers, and even ditches. After being transplanted they at once make themselves at home in a new environment and very soon begin to breed, even if the temperature and water is different from their natural habitat. Some species are viviparous and sometimes produce six broods of young in one season. If hungry, the mother devours her own young as rapidly as they are born. The young at the time of birth, while very small, are vigorous, coming into the world with an appetite well prepared to enter upon an independent career, and soon make rapid growth; indeed such is the extreme prolificness of some species that they begin to breed before they are four months old. These few of the many interesting facts that could be quoted are enough to show that either indifference or ignorance is the only reason why many game-fish waters are almost entirely void of this valuable species of fish food. Minnows may be easily collected in their favorite haunts of small brooks and ditches with small, fine-meshed seines, then transferred to 10-gallon milk cans, by which means they could be shipped and introduced into the lakes and streams where game-fish are most abundant. In lakes and rivers of large extent, where big fish, like muskellunge and lake trout, abide, the supply of food is never overabundant, and the introduction of entirely different species of fish food is of the greatest value, whether the adult species be small or grow to a fair size. All assist directly or indirectly to make game-fish more plentiful. Wherever trout or other game-fish feed upon one species alone - as instanced in another chapter of trout-eating young sunfish exclusively - it is not so desirable either for fish or angler, because it induces trout to congregate in restricted localities hard for the angler to find, and doubtless from the standpoint of eating not so good as a varied diet. In most lakes the young of perch, dace, and chub furnish the chief food for pickerel and pike if the young of their own kind are not overplentiful, but in later years their growth has been limited. Large fish are quite scarce, for the average caught are small compared with what were captured years ago, when three-pound pickerel and ten-pound pike were common. If fish do arrive at an adult state, anglers do not seem to be skilful enough to get them, as we hear of many being picked up dead, having died of old age or disease. Like men, these very old fish are not voracious. They feed little; long intervals elapse between meals. When they do take a notion to eat, they invariably devour a large fish, almost their own size; gorge it slowly, and then rest sometimes for many weeks. This trait in the pike family is not apparent in the trout, which are continuously hungry, feeding all the time on what food is available. Indeed of the many large fish I have opened it is quite rare to find food in their stomachs when captured at evening.
In many lakes and streams, by some means or other, different species of fish have been planted that in the past have been considered detrimental to each other; such as brown trout with brook-trout, or bass with any species of trout. So far as my observation goes, I find it makes very little or no difference in the survival of one or the other so far as antagonism goes. But it makes a vast difference if each separate species is planted in the proper environment, and where suitable food is available to it. If so, they are sure to prosper and multiply. Trout love aerated parts of rivers; bass prefer deep, placid pools, where bottom food is easily available to them, with periodical trips to the shallows after minnows. If adult trout and bass meet, the advantage in combat, should they desire such, is with the trout, for the back spine of a bass is no match against the array of large teeth with which all trout are well supplied. The teeth of bass are no more formidable than if they had rough sandpaper on the edge of their jaws.