THE FISH 239 



fishes, as sticklebacks, sunfish, toadfish, etc., make nests, but 

 visually the eggs are left to develop by themselves, sometimes 

 attached to some submerged object, but more frequently free in 

 the water. In some eggs a tiny oil drop buoys up the egg to the 

 surface, where the heat of the sun aids development. They are 

 exposed to many dangers, and both eggs and developing fish are 

 eaten, not only by birds, fish of other species, and other water in- 

 habitants, but also by their own relatives, and even parents. 

 Consequently a very small percentage of eggs ever produce ma- 

 ture fish. 



The Relation of the Spawning Habits to Economic Importance 

 of Fish. — The spawning habits of fish are of great importance to 

 us because of the economic value of fish to mankind, not only 

 directly as a food, but indirectly as food for other animals in turn 

 valuable to man. Many of our most desirable food fishes, notably 

 the salmon, shad, sturgeon, and smelt, pass up rivers from the 

 ocean to deposit their eggs, swimming against strong currents 

 much of the way, some species leaping rapids and falls, in order 

 to deposit their eggs in localities where the conditions of water 

 and food are suitable, and the water shallow enough to allow 

 the sun's rays to warm it sufficiently to cause the eggs to develop. 

 The Chinook salmon of the Pacific coast, the salmon used in the 

 Western canning industry, travels over a thousand miles up the 

 Columbia and other rivers, where it spa^vns. The salmon begin 

 to pass up the rivers in early spring, and reach the spav/ning beds, 

 shallow deposits of gravel in cool mountain streams, before late 

 summer. Here the fish, both males and females, remain until 

 the temperature of the water falls to about 54° Fahrenheit. The 

 eggs and milt are then deposited, and the old fish die, leaving the 

 eggs to be hatched out later by the heat of the sun's rays. 



Need of Conservation. — The instinct of this and other species 

 of fish to go into shallow rivers to deposit their eggs has been 

 made use of by man. At the time of the spawning migration the 

 salmon are taken in vast numbers, for the salmon fisheries net 

 over $16,000,000 annually. 



But the need for conservation of this important national asset 

 is great. The shad have within recent time abandoned their 



