THE VERTEBRATE ANIMALS 



281 



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. ]\Iany 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 

 (jf the way, some spe- 

 cies leaping rapids and 

 falls, in order to de- 

 liosit their eggs in 



SIWkM- 



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\ 



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Salmon leaping a fall on their way to their 

 spawning beds. Photographed by Dr. John 

 A. Sampson. 



suitable localities, where 

 the conditions of water 

 and food are requisite, 

 and the water shallow 

 enough to allow the sun's 

 rays to warm the water 

 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 spawns. The salmon begin to pass up the 

 rivers in early spring, and reach the spawning beds, .shallow de- 

 posits of gravel in cool mountain streams, before late summer. 

 Here the fish, both males and females, remain until tlie temperature 

 of the water falls to about .54° Fahrenheit. The eggs and milt arc 

 then deposited, and the old fish die, leaving the (■ggs in he hatched 

 out later by the heat of the sun's rays. 



