84 



THE GROWTH AND VARIATION OF FISH. 



How can you tell the age of a fish? stant temperature, and at one usually 



This question is often asked and just so much higher than the medium in which 



often is the answer unsatisfactory. he lives. 



A fish is a cold-blooded animal ; that is, As an example of the ability of fishes 

 his temperature is nearly the same as to go for some time without eating, we 

 that of the water in which he lives. His need only mention our Pacific salmon, 

 circulation is sluggish and his appetite is There are five species of these large fishes 

 a variable quantity. He has the capacity on the Pacific coast. In the early spring 

 to take in large quantities of food at one (April) many of the largest species, the 

 meal and properly assimilate it ; on the Chinook, start up the Columbia river for 

 other hand he is able to fast for weeks at the purpose of spawning. They reach 

 a time. He has his own notions about the headwaters of the Columbia in Idaho 

 eating, and it is quite impossible to in- early in September. During this journey 

 duce him to change them, and all this has they eat nothing. We know they do not 

 considerable influence on his rate of eat, for of the thousands caught each 

 growth. It is out of the question to ex- year for the canneries none are found 

 pect him to grow when he is fasting ; on with food in their stomachs ; besides, this 

 the other hand he must draw on the fat organ has become much shrunken. If 

 he has stored up in his body to furnish they did eat on this journey there would 

 him energy for his muscular movements not, I believe, be enough animal and plant 

 and to carry on the ordinary functions of life in the Columbia to furnish each sal- 

 nutrition. The fish here has an advant- mon with more than one meal. Now 

 age over the warm-blooded animals, for many of them make the journey against a 

 he does not need to generate heat to keep strong current for more than one thou- 

 his body at a constant temperature. The sand miles, and reach an elevation of 

 amount of food often eaten at one time is about eight thousand feet above the sea. 

 quite remarkable. I remember once of When they leave the ocean they are in ex- 

 taking nearly one pound of sunfish from cellent condition, by the time they have 

 the stomach of a Large-mouthed Black reached their journey's end they are thin 

 Bass. This does not indicate that a bass and haggard, their vitality is so reduced 

 must eat such meals three times each day, that soon after spawning they die liter- 

 it only shows his capacity to make use of ally die of starvation. Their eggs hatch 

 a large quantity of food when it is abund- during the winter. By the next winter 

 ant and his stomach feels the need of it. the young salmon are from four to five 

 A trout is a good feeder ; his stomach inches in length, and by the following fall 

 and mouth are large, much in size like or early winter they go to the sea, having 

 that of the black bass. From experi- reached an average length of about ten 

 ments conducted at Neosho, Missouri, by inches. After leaving the fresh water, 

 Mr. Page, he found that a young trout which only afforded them a scant subsist- 

 did best on a .daily ration of solid food ence for nearly two years, the generous 

 equal to about seventy-five per cent ocean gives them plenty of sea room and 

 of its weight. On this amount the an abundance of food, which in a few 

 trout would reach an average length years prepares them to repeat the long 

 of six inches in one year. The av- journey of their parents. We are, in case 

 erage amount of solid food con- of most fishes, ignorant of their life his- 

 sumed daily by a man is from one and tories, as we are of the salmon's. We 

 one-half to two per cent of his weight, or know the average rate of growth of the 

 more than twice that consumed by our salmon for the first two years, but we 

 active, growing young trout. As men- know nothing more of them until they 

 tioned before, the trout is relieved from return to fresh water to spawn, 

 generating heat to keep his body at a con- I mentioned that trout in the Neosho 



