(near or south of lat. 50^N) but were now mainly 

 in the Transition Area. Bakkala (1971) noted a 

 similar situation in the summer; immatures were 

 usually found in the Ridge Area south of the 

 eastern Aleutian Islands and Alaska Peninsula, 

 but when the Alaskan Stream extended farther 

 offshore, the geographical distribution of salmon 

 was unchanged and the immature salmon were in 

 both the Alaskan Stream and Ridge Areas. His 

 data also demonstrated that whereas immatures 

 south of the eastern Aleutian Islands and Alaska 

 Peninsula were found mainly in the Ridge Area, 

 those south of the central Aleutian Islands were 

 most abundant in the Alaskan Stream. The 

 Alaskan Stream was previously thought to be the 

 major route of westward migration for salmon, but 

 westward migration occurred in the Ridge Area 

 as well. The Subarctic Current, a term used to 

 describe the faster moving waters near the 

 boundary of the Western Subarctic Intrusion and 

 Transition Areas, was also hypothesized to be a 

 route of eastward movement by maturing sockeye 

 salmon in fall and winter, but most maturing 

 fish are far north of this current and probably 

 move east in Ridge Area waters. 



In summary, it could not be demonstrated that 

 defined oceanographic features of the North 

 Pacific Ocean had any direct influence on the 

 north-south movements and distribution of 

 sockeye salmon. Their movements and distribu- 

 tion may be governed by other environmental 

 conditions such as water temperature or food 

 abundance. 



FISHERY BULLETIN: VOL. 72, NO. 2 



Research vessel catch data and the variable 

 numbers of Bristol Bay sockeye available to the 

 Japanese mothership fishery indicate that matur- 

 ing Bristol Bay sockeye make eastward migra- 

 tions in the North Pacific Ocean in the fall or 

 winter and that the proportion of Bristol Bay 

 fish making this migration or the extent of these 

 migrations vary between some years. This is per- 

 haps influenced by the interaction of the Alaskan 

 and Western Subarctic Gyres and possibly by the 

 recirculation of Alaskan Stream waters. Matur- 

 ing Bristol Bay sockeye are found mainly in the 

 Alaskan Gyre in spring, and if the westward 

 extent of this gyre is limited by the strength 

 of the Western Subarctic Gyre, the westward dis- 

 tribution of maturing sockeye may also be 

 limited. (See Figure 24 for the location of the 

 two gyres.) We have no direct evidence to support 

 this possibility. 



MODEL OF MIGRATION OF BRISTOL 

 BAY SOCKEYE SALMON 



From the accumulated knowledge of distribu- 

 tion and migration of Bristol Bay sockeye salmon, 

 we have diagrammed a model of their movements 

 from the time they leave the estuary until 

 they return. The model differs from that given 

 by Royce et al. (1968), but the two models are 

 in agreement in regard to the major areas in 

 which the salmon are found. 



I70°E 



Figure 24. — Schematic diagram of surface circulation in the Subarctic North Pacific to illustrate 

 the general location of the Alaskan and Western Subarctic Gyres (from Dodimead, Favorite, and 

 Hirano, Figure 109, 1963). 



610 



