Feeding Ecology of Juvenile Chinook Salmon Along the West Coast of North America

The marine survival of Chinook Salmon (Oncorhynchus tshawytscha) is thought to be linked to changes in oceanic conditions that alter the quantity and quality of food available during their early marine life. To compare the feeding ecology of juvenile Chinook Salmon across their North American range, we collected zooplankton and juvenile Chinook Salmon in coastal marine waters from northern California to the eastern Bering Sea. We used a combination of stomach contents and stable isotopes of nitrogen (δ¹⁵N) and carbon (δ¹³C) to characterize their feeding ecology. We found strong regional differences in prey utilization by Chinook Salmon. With growth and ontogeny, Chinook Salmon in all regions became equilibrated with oceanic isotopic values. δ¹³C values corresponded with expected regional differences in primary productivity. δ¹⁵N values generally corresponded with stomach contents. Dietary niche, as indicated by stable isotopes, corresponded with expected dietary diversity from stomach contents. Our results show strong differences in feeding ecology of juvenile Chinook Salmon are mainly influenced by growth-driven differences in body size and regional productivity.