i6o 



Instincts, Habits, and Adaptations 



in the rivers, and a few pass more or less indiscriminately 

 from one kind of water to another. 



Migratory Fishes. — The movements of migratory fishes are 

 mainly controlled by the impulse of reproduction. Some pelagic 



fishes, especially those of the 

 mackerel and flying-fish families, 

 swim long distances to a region 

 favorable for the deposition of 

 spawn. Others pursue for equal 

 distances the schools of men- 

 haden or other fishes which ser\^e 

 as their prey. Some species 

 are known mainly in the waters 

 they make their breeding homes, 

 as in Cuba, Southern Cali- 

 fornia, Hawaii, or Japan, the 

 individuals being scattered at 

 other times through the wide 

 seas. 



Anadromous Fishes. — Many 

 fresh-water fishes, as trout and 

 suckers, forsake the large streams 

 in the spring, ascending the 

 small brooks where their young 

 can be reared in greater safety. 

 Still others, known as anadromous 

 fishes, feed and mature in the 

 sea, but ascend the rivers as the 

 impulse of reproduction grows 

 strong. Among such fishes are the salmon, shad, alewife, stur- 

 geon, and striped bass in American waters. The most remark- 

 able case of the anadromous instinct is found in the king salmon 

 or qtunnat {Oncorhyiichns ischaivytsclia) of the Pacific Coast. 

 This great fish spawns in November, at the age of four years 

 and an average weight of twenty-two pounds. In the Columbia 

 RiA-er it begins running with the spring freshets in March and 

 April. It spends the whole summer, without feeding, in the 

 ascent of the ri\'er. By autumn the individuals have reached 

 the mountain streams of Idaho, greatly changed in appearance, 



Fig. 122. — Portuguese Man-of-war 

 Fish, Gohiomorus gronovii. Family 

 Siroinateidiie. 



