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I'm sure the headline won't shock anyone here, however a new published report in the Canadian Journal of Fisheries and Aquatic Sciences will hopefully garner more attention from government, NGOs, and others looking to solve chinook abundance issues. Study also shows that for 20 wild chinook populations, there were no significant negative relationships between hatchery abundance and productivity of wild stocks in WA, BC.
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.
http://www.nrcresearchpress.com/doi/pdf/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.
http://www.nrcresearchpress.com/doi/pdf/10.1139/cjfas-2017-0481
