Regional and inter-annual trends in marine growth of juvenile salmon in coastal pelagic ecosystems of British Columbia, Canada

Abstract

We measured insulin-like growth factor 1 (IGF1) concentrations (a proxy for growth) from juvenile coho Oncorhynchus kisutch, sockeye O. nerka, chum O. keta, and Chinook salmon O. tshawytscha collected in 8 regions of British Columbian coastal waters, in June of 2009, 2010, and 2011. We found annual differences in IGF1 for all 4 species, as well as species- specific regional differences in IGF1 concentrations in coho, chum, and sockeye salmon. Sockeye and chum salmon had consistently higher levels in the northern regions of the Dixon Entrance, Haida Gwaii, Hecate Strait, and lower levels in Queen Charlotte Strait. Regional differences in coho, chum, and sockeye salmon were highly correlated (R 2 = 0.61-0.75). These results demonstrate that salmon growth responds to local environmental variability on a scale of several hundred kilo- meters. Thus, IGF1 measures should generate insight into fish production on relatively local regional and temporal scales, and these same measures may allow the assessment of how habitats vary on these same scales.