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CIVIC BIOLOGY 



Professor Forbes of the University of Illinois lias made a special 

 study of the foods of fishes. He has found that with most fishes foods 

 change with age, the life of a fish being, in fact, divided into two and 

 often three distinct periods. In the first, which we may call the " fry " 

 period, from hatching to one or two inches in length, all species feed 

 on small Crustacea. In the firigerling stage, from one or two to four 

 inches, they feed largely on insects but begin to devour their smaller 

 fellow fishes as well.' When adult, the larger species feed chiefly upon 



Fio. 144. Visiting Municipal Fish Market, Cleveland, Ohio 

 Class learii to distinguish fresh rish by the red gills and the uusunken eyes 



smaller fishes, while the smaller species continue to feed mostly on 

 insects. Adult fishes possessing fine gill rakers continue to strain out 

 the minute Crustacea; those with heavy, blunt teeth feed largely on mol- 

 lusks; and worms play but a small part in the food of fresh-water fishes. 



Spawning habits and seasons. Brooks' s law, as stated in its 

 application to the lobster, with the diagrams illustrating it, 

 applies with equal force to food and game fishes. With the 

 powerful machinery at his disposal, man strikes all species 

 as a catastrophe and not as their natural enemy ; and he 

 must make good his attack by intelligent dominion or lose 



