A NEW MODEL OF OCEAN MIGRATIONS OF 

 BRISTOL BAY SOCKEYE SALMON 



Robert R. French and Richard G. Bakkala' 



ABSTRACT 



A model is presented that describes the ocean migrations of Bristol Bay sockeye salmon from 

 the time the fish leave the estuary until they return as adults. Bristol Bay sockeye salmon 

 inhabit extensive areas of the ocean during various stages of their life at sea, ranging across 

 most of the North Pacific Ocean from about long. 140°W to near long. 167'E and from near 

 lat. 46'N to lat. 58^N in the central Bering Sea. Initially, their migration route takes the young 

 juveniles from the eastern Bering Sea through the central and eastern Aleutian Islands passes 

 to south of lat. 50^N where in late winter they become broadly distributed across the North 

 Pacific Ocean. In June the immature fish start a northward movement and in summer occupy 

 waters from lat. 50'N to the Aleutian Islands and over an east-west area from long. 160^W to 

 170'E; part of the population moves north into the Bering Sea. The following winter the sockeye 

 separate into immature and maturing components. Those that will mature remain in waters 

 north of lat. SCN from whence they will migrate back to Bristol Bay in the spring with the 

 major proportion entering the Bering Sea through passes east of long. 175°W. The immature fish 

 that will remain at sea another year move south of lat. 50°N in the winter and early spring, 

 then essentially repeat the migration they had made the previous summer. These fish as maturing 

 fish the following winter and spring follow the same migration route as the earlier maturing group. 

 No direct relationship was found between the distribution and migration of the sockeye and 

 defined oceanographic features of the Subarctic Region of the North Pacific Ocean. 



A model of the complete ocean migrations of sock- 

 eye salmon, Oncorhynchus nerka, from Bristol 

 Bay, Alaska, was originally developed by Royce, 

 Smith, and Hartt (1968). Their model suggested 

 that Bristol Bay sockeye during their life at sea 

 make two or three circuits of an elongated east- 

 west course extending from about long. 165°E to 

 140°W in the North Pacific Ocean and Bering Sea. 

 These migrations were thought to be associated 

 with major currents of this region — the Alaskan 

 Stream and Subarctic Current. 



Since formulation of the model by Royce et al. 

 (1968), Bakkala (1971) studied the distribution 

 and abundance of immature sockeye salmon in 

 relation to ocean currents and other features of 

 the Subarctic Region and suggested certain refine- 

 ments to the earlier model. New information 

 available through continued offshore studies com- 

 bined with a review of existing tagging data has 

 led us to propose a new model of migration of 



'Northwest Fisheries Center, National Marine Fisheries 

 Service, NOAA, 2725 Montlake Boulevard East, Seattle, WA 

 98112. 



Manuscript accepted October 1973. 

 FISHERY BULLETIN; VOL. 72, NO. 2, 1974. 



Bristol Bay sockeye to supplement that proposed 

 by Royce et al. (1968). 



Studies of the oceanic distribution of Pacific 

 salmon have shown sockeye salmon from Bristol 

 Bay, Alaska, to be widely distributed in the 

 North Pacific Ocean and Bering Sea. Tagging 

 experiments have shown that Bristol Bay sockeye 

 salmon range from about long. 140°W, approxi- 

 mately 111 km from the coast of southeastern 

 Alaska, to near long. 167°E, approximately 463. 

 km from the coast of Kamchatka, an east-west 

 distance of about 3,700 km. From south to north, 

 Bristol Bay sockeye have been identified near 

 lat. 46°N in the northeastern Pacific Ocean to near 

 lat. 58°N in the central Bering Sea. Notwith- 

 standing their broad distribution and dynamic 

 movements, the basic distribution and seasonal 

 migrations of the sockeye are known. 



In this report we examine data from tagging 

 experiments and salmon catches in relation to 

 environmental features to describe the distribu- 

 tion and migration of Bristol Bay sockeye salmon 

 from the time they leave the estuary until they 

 return as maturing fish. Following these discus- 

 sions, a model of migrations for Bristol Bay 

 sockeye salmon is presented. 



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