How can you tell the age of a fish? This question is often asked and just so often is the answer unsatisfactory.

A fish is a cold-blooded animal; that is, his temperature is nearly the same as that of the water in which he lives. His circulation is sluggish and his appetite is a variable quantity. He has the capacity to take in large quantities of food at one meal and properly assimilate it; on the other hand he is able to fast for weeks at a time. He has his own notions about eating, and it is quite impossible to induce him to change them, and all this has considerable influence on his rate of growth. It is out of the question to expect him to grow when he is fasting; on the other hand he must draw on the fat he has stored up in his body to furnish him energy for his muscular movements and to carry on the ordinary functions of nutrition. The fish here has an advantage over the warm-blooded animals, for he does not need to generate heat to keep his body at a constant temperature. The amount of food often eaten at one time is quite remarkable. I remember once of taking nearly one pound of sunfish from the stomach of a Large-mouthed Black Bass. This does not indicate that a bass must eat such meals three times each day, it only shows his capacity to make use of a large quantity of food when it is abundant and his stomach feels the need of it. A trout is a good feeder; his stomach and mouth are large, much in size like that of the black bass. From experiments conducted at Neosho, Missouri, by Mr. Page, he found that a young trout did best on a daily ration of solid food equal to about seventy-five per cent of its weight. On this amount the trout would reach an average length of six inches in one year. The average amount of solid food consumed daily by a man is from one and one-half to two per cent of his weight, or more than twice that consumed by our active, growing young trout. As mentioned before, the trout is relieved from generating heat to keep his body at a constant temperature, and at one usually much higher than the medium in which he lives.

As an example of the ability of fishes to go for some time without eating, we need only mention our Pacific salmon. There are five species of these large fishes on the Pacific coast. In the early spring (April) many of the largest species, the Chinook, start up the Columbia river for the purpose of spawning. They reach the headwaters of the Columbia in Idaho early in September. During this journey they eat nothing. We know they do not eat, for of the thousands caught each year for the canneries none are found with food in their stomachs; besides, this organ has become much shrunken. If they did eat on this journey there would not, I believe, be enough animal and plant life in the Columbia to furnish each salmon with more than one meal. Now many of them make the journey against a strong current for more than one thousand miles, and reach an elevation of about eight thousand feet above the sea. When they leave the ocean they are in excellent condition, by the time they have reached their journey's end they are thin and haggard, their vitality is so reduced that soon after spawning they die—literally die of starvation. Their eggs hatch during the winter. By the next winter the young salmon are from four to five inches in length, and by the following fall or early winter they go to the sea, having reached an average length of about ten inches. After leaving the fresh water, which only afforded them a scant subsistence for nearly two years, the generous ocean gives them plenty of sea room and an abundance of food, which in a few years prepares them to repeat the long journey of their parents. We are, in case of most fishes, ignorant of their life histories, as we are of the salmon's. We know the average rate of growth of the salmon for the first two years, but we know nothing more of them until they return to fresh water to spawn.

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.

The Blind Fishes, which inhabit caves in this country, are very interesting. They have lost their color, if they ever had any, being white. In many the eyes have become so degenerated as to be entirely of no service when the fish is in the light. The head is furnished with tactile organs, which enables them to feel their way in the dark. In fact, they are well adapted for the life they lead. Dr. Eigenmann tells us that Blind Fishes were not accidentally swept into caves or driven there by their enemies, "but entered them deliberately and avoided coming out into the light." In other words, they preferred "darkness rather than light." Having simplified eyes and highly developed sense organs, they were able to live in the dark. The many ages they have lived in the caves has better fitted them for their existence in total darkness. The Blind Fishes were not always blind, but have become so because of their own preferences.

The readers are, if they will only study fishes, sure to find them extremely interesting. There are a wonderful variety of fishes, each well adapted for the life it leads. You will find them in the brooks, creeks, rivers and lakes or ocean, wherever you happen to be, and you are sure to be highly repaid for all the study or attention you may give them.

Seth E. Meek.