Marine growth patterns of southern British Columbia chum salmon explained by interactions between density-dependent competition and changing climate

Thirty-nine years of scale growth measurements from Big Qualicum River chum salmon (Oncorhynchus keta) in southern British Columbia demonstrated that competition and climate variation affect marine growth and age at maturity. A longitudinal study design that accounted for correlation among individuals revealed growth at all ages was reduced when the biomass of North American chum, sockeye (Oncorhynchus nerka) and pink salmon (Oncorhynchus gorbuscha) was high. When North Pacific Gyre Oscillation (NPGO) was positive, indicating increased primary productivity, predicted growth increased. Climate variation also affected these competition effects. Density-dependent competition effects increased when NPGO became more positive and Pacific Decadal Oscillation more negative (indicating cool conditions), causing the greatest range in predicted scale size. Chum salmon are likely to exhibit continued reduction in growth at age due to increased ocean temperatures driven by climate change and high aggregate salmon biomass that includes hatchery releases. If evidence of biomass and climate effects presented here are common among Pacific salmon populations, reduction of hatchery releases should be considered.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author