Oceanic feeding habits of chinook salmon, Oncorhynchus tshawytscha, off northern California

The chinook salmon, Oncorhynchus tshawytscha, is an important commercial and recreational species inhabiting rivers and nearshore coastal waters from San Diego, California, to the Bering Sea and Japan (Miller and Lea, 1972). Many West Coast populations are in a serious decline (Pearcy, 1992). Nehlsen et al. (1991) reported an overall decrease in salmonid numbers in the coastal waters of the Pacific Northwest and suggested that northern California chinook salmon runs may be at high risk of extinction owing to 1) habitat damage and mainstream passage problems; 2) overharvesting; and 3) hybridization, predation, competition, disease, and poor ocean survival conditions. Surprisingly, little research has been done off the northern California coast regarding the diet of salmonids during oceanic migrations.