Wild Chinook salmon productivity is negatively related to seal density, and not related to hatchery releases in the Pacific Northwest

• Main Authors: Nelson, Benjamin W, Walters, Carl J, Trites, Andrew W, McAllister, Murdoch K.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: NRC Research Press (a division of Canadian Science Publishing) 2018
• Subjects: Pacific; harbour seal; Phoca vitulina
• Online Access: http://hdl.handle.net/1807/90768; http://www.nrcresearchpress.com/doi/abs/10.1139/cjfas-2017-0481

Predation risk and competition among conspecifics significantly affect survival of juvenile salmon, but are rarely incorporated into models that predict recruitment in salmon populations. Using densities of harbour seals (Phoca vitulina) and numbers of hatchery-released smolts as covariates in spatially-structured Bayesian hierarchical stock-recruitment models, we found significant negative correlations between seal densities and productivity of Chinook salmon (Oncorhynchus tshawytscha) for 14 of 20 wild Chinook populations in the Pacific Northwest. Changes in numbers of seals since the 1970s were associated with a 74% decrease (95% CI: -85%, -64%) in maximum sustainable yield in Chinook stocks. In contrast, hatchery releases were significantly correlated with Chinook productivity in only one of 20 populations. Our findings are consistent with recent research on predator diets and bioenergetics modeling that suggest there is a relationship between harbour seal predation on juvenile Chinook and reduced marine survival in parts of the eastern Pacific. Forecasting, assessment, and recovery efforts for salmon populations of high conservation concern should thus consider including biotic factors, particularly predator-prey interactions. 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.