The Salmon and Trout of Japan. 



BY 



David Starr Jordan. 



Of all the families of fishes none offer greater difficulties to the 

 student of classification than the Salmonidcc. This is due to the ex- 

 tremely close relation existing among the species themselves and to the 

 great range of variation offered by the individuals. No fishes respond 

 more quickly to the influences of environment, none vary so greatly with 

 the conditions of food supply, and none show greater changes with the 

 different conditions of seasonal and sexual development. 



Having carefully examined all the many specimens of salmon and 

 trout obtained by Mr. Snyder and myself in the waters of Japan, iu the 

 summer of 1900, I am able to point out the distinctive characters of the 

 species represented in this collection, which includes all the species thus 

 far ascribed to the Japanese fauna. 



1. The Sake or Dog Salmon ; Oncorhynchus keta (Walbaum). 



The genus Oncorhynchus Suckley includes the salmon of the North 

 Pacific, six known species in all. It is characterized by the increased 

 number of anal rays, branchiostegals and gill rakers. Its species are 

 resident in the sea, ascend the rivers to spawn, do not feed iu the 

 spawning season, and hence except when land-locked do not feed in fresh 

 waters. The males become hook-jawed and greatly distorted in the 

 spawning season, and after depositing the eggs and milt all of both sexes 

 die. 



The largest of the Japanese salmon is the Sake, called Dog Salmon 

 on the American coast and Haiko in Siberia, Oncorhynchus keta 

 (Walbaum). It reaches a weight of 10 to 15 pounds and runs in the fall 

 in the rivers of Hokkaido and northern Hondo. In the character of its 



