76 



THE MIGRATION AND CONSERVATION OF SALMON 



Fig. 1. The Alaska Peninsula and Bristol Bay Eegions. 



a longer or shorter time the fish would be 

 caught in a stronger fresh-salt water gradi- 

 ent and move through Isanotski Strait into 

 Bering Sea. Once in Bering Sea the fresh- 

 salt water gradient is toward the Bristol 

 Bay streams from which there is a west- 

 ward drift to Unimak Pass and westward 

 but some of the water passing through Isa- 

 notski Strait to the Pacific. When the red 

 salmon reach Bering Sea, they, according 

 to observations (Gilbert, 1924, and Gilbert 

 and Rich, 1927a) lose no time in reaching 

 a spawning ground area. All waters 



emerging from Isanotski Strait have been 

 thoroughly mixed. All will agree with and 

 none can object to this statement. In short, 

 there is an irregular fan-shaped fresh-salt 

 water gradient from Isanotski Strait to the 

 Bristol Bay area. The red salmon not de- 

 stined to any particular stream are follow- 

 ing a gradient which at times is quite irreg- 

 ular. A fish may be following a gradient 

 dominated at the time by one stream and 

 for one reason or another be switched to a 

 gradient dominated by an entirely different 

 stream. Now, the Shumagin Islands can 



