I mentioned that trout in the Neosho Fish Hatchery grew, under favorable circumstances, to a length of six inches in one year. It must not be taken for granted, however, that trout six inches in length are one year old. In their native streams, in cooler regions, they will not often attain this length in two or more years.

In general we do not find large fishes in small bodies of water; neither do we find the fish in our small aquaria growing at an alarming rate. The fish disdains to outgrow his surroundings; he may feel his importance, and consider himself in many ways superior to the other fishes in the pond with him, but he will not permit himself to grow to such a size as to make the question of securing a living a difficult or irksome one.

Fishes spawn but once each year, and the time and length of the spawning season is not the same for all species. With some species the season is short, while with others it may extend through three or more months. In the latter case those produced the first part of the spawning season are at the end of six months much larger than those which appear at the close. It is therefore evident that the fishes of any single brood by the end of the year will vary greatly in size, often to such an extent that the broods of one season cannot be separated from those of the preceding season; especially is this true of our smaller species. Mr. Moenkhaus, in making a study of the two species of darters, the Sand Darter or "Johnny," and the Log Perch, found by collecting a large, miscellaneous lot of these fishes, from a given locality, that it was possible to separate them in groups according to size of one, two or three years of age, which indicates a quite uniform rate of growth for these two species.

Mr. Voris collected a miscellaneous lot of over five hundred specimens of the Blunt-nosed Minnow from Turkey Lake in Indiana, varying from one to three inches in length. These, when separated as far as possible, according to sizes, did not fall into distinct groups of different ages. In my own collecting and study of fresh water fishes I have always been impressed with the difficulty of recognizing the age of fishes, except that the smallest taken was considered to be the product of the preceding spawning season. Here is an interesting question to which but little attention has been given. Any one will find much interest in studying the rate of growth of fishes under different circumstances. We know that the rate of growth is in no way uniform, as is the case with our warm-blooded animals. We also know that among fishes there is no uniform adult size, as there is in case of warm-blooded animals (birds and mammals). In general, we cannot speak of a fish as being full-grown; at the same time there seems to be a limit of size for each species in each body of water, beyond which only a few go. The Chinook salmon we mentioned reach an average weight of twenty to thirty pounds, although individuals are occasionally taken of forty, sixty or even one hundred pounds weight. These large fishes are by no means common, the other species of salmon never attain the size of the Chinook.

There is an interesting family of fishes in our fresh waters known as Minnows; these fishes are too small and too full of bones to become a favorite for the table. They are the most helpless of all our fresh water fishes, being soft, and, as they are slow swimmers, they become an easy prey to larger fishes, and form a large part of their food supply. They have been constantly driven into smaller streams and shallow water, until they have become exceedingly dwarfed. Their only use in the economy of fish life seems to be to assimilate small organisms, converting them into such shape that they can be taken by the larger fishes. Now the Minnows of all the United States east of the Rockies are small and, except in case of a few species, they are less than six inches in length. The predatory fishes, such as the Sunfishes and Perches, Pike and Pickerel, are their worst enemies. In the Rocky Mountains there are none of these fishes, and many minnows there grow to a length of two feet or more. The only enemy of importance they have is the trout, but the minnow finds a more congenial climate in the larger bodies of water, too warm for the trout. The struggle for existence has been a severe one, especially so in our streams where species of fish are the more numerous. It has greatly limited the growth of most species beyond an average size, and is in many places responsible for the fact that often a species may become dwarfed in certain bodies of water. In the Salmon river in Idaho it was not an uncommon thing to catch trout of three or four pounds weight. In the smaller tributaries and in the smaller mountain lakes it was unusual to catch one weighing over one-half pound, the average being less than one-fourth pound. I have no doubt that many of those from the small lakes of one-half pound were as old as the large ones taken from the Salmon river.

Fish eat and grow very irregularly. The average size of individuals, which we would ordinarily call adults, for some species, is different in different bodies of water. Their growth is influenced largely by the size and depth of the body of water in which they live, also by its temperature and the amount of suitable food it contains. The value or extent of each of these influences is imperfectly understood.

The forms of fishes are very numerous. Some are extremely long and slender, as many of the species of Eels, Pipe-fishes and the like, while others are extremely short, like Sunfish of the ocean. Others, like the Trunk Fishes, are nearly equal in all dimensions. The average form and the one which best suits our idea of a fish, is the Black Bass, or other fishes of similar pattern. To know the advantages of these forms one must study the fishes in their native element. The peculiar forms which many species take are the most noticeable in those found in the tropics. The struggle for existence there is the most severe, and it seems as if each species had labored to take on some peculiar form which would assist most in its preservation. In this respect color also plays an important factor. It is in the tropics and among the many species of corals that we find the most highly-colored fishes.

Many fishes have the power to change their color, and this they can do in a very short time. The flounders are a peculiar family, the young when born are symmetrical. Early in life they take on the habit of their parents and lie on one side, the eye on the underside disdains to look downwards and so begins to move toward the other side. The bones of the head suit themselves to this change and soon our flounder has both eyes on the same side of the head. The upper side is colored much to resemble sand, and the under side becomes nearly white. The flounder protects himself by covering his body, except the eyes, with sand. Flounders live on sandy bottoms, some in shallow water, while others are found in deepest parts of the ocean. If flounders are placed in an aquarium and arranged so the light can fall on the under side of their bodies, this, too, becomes dark, much like the other side.

It is interesting to study the habits of fishes in a small aquarium, and to especially notice their ability to change color, and how rapidly they do it. So many persons seem to be saturated with the idea that an aquarium must have in it one or more gold fish. This seems to me to be a mistake when our streams contain so many species suitable for the aquarium which are far more handsome than the gold fish, and which, if you give them half a chance, will teach you something of interest. Mr. Ford, of Berwyn, Illinois, has a small aquarium, in his house, in which he keeps from fifteen to twenty-six species of native fishes. Among these are several species of Darters, the most beautifully colored and the most interesting of all our fresh-water forms. Then there are Minnows, Suckers, Catfishes, Sunfishes, the Pike, Mud Minnow, Top Minnow, and so on. To one who would know fishes, any one of these species is more desirable than gold fish. The study of fishes in an aquarium, such as the one possessed by Mr. Ford, is extremely interesting. They will teach you much about their habits, besides giving you many lessons showing their ability to change color and adapt themselves to their surroundings.

A MOUNTAIN LAKE.CHICAGO:
A. W. MUMFORD PUBLISHER.