THE ALLIES OF THE PERCH 



325 



The adult salmon live in the ocean. When sexually ma- 

 ture they leave the ocean and by way of the rivers seek lakes 

 and streams as spawning grounds. It seems fairly certain 

 that the adult fishes return to the same waters where they 

 were born. The mature salmon which escapes the fisher- 

 man makes its way upstream, frequently for several hun- 

 dred miles. No food is taken after the fish enters fresh water. 



Fig. 167. Flatfish 

 From Report of Fur-Seal Investigations 



It seems to have but one object, that of reaching the breed- 

 ing grounds. Waterfalls and even some types of dams do 

 not deter the migration, for by persistent effort some individ- 

 uals finally succeed in leaping over such obstacles. After the 

 eggs have been laid and fertilized the adults of both sexes 

 die, never living to return to the sea. From the spawning 

 grounds the young salmon migrate to the sea, where they 

 live for from three to five years before becoming mature 

 and ready to ascend the streams to the breeding grounds. 

 Flatfishes. The flatfishes (including among other fishes 

 the flounders and halibuts) are a family of compressed 

 fishes, dark on one side and light on the other, which lie on 

 their light side on the bottom of the sea (Fig. 167). When 



