Evaluating benefits of stocking on sockeye recovery projections in a nutrient-enhanced mixed life history population

Dam construction often blocks migration of anadromous sockeye salmon (Oncorhynchus nerka), resulting in a residualized population that is often managed as landlocked kokanee. Anadromy resumes when a reconnection to the ocean is established, however there may be selective pressure acting on threshold trait(s) affecting smolt timing and probability. While there may be interest in predicting persistence of anadromous and residual sockeye forms, this is difficult because the heritability of smolting in these populations is poorly known. We develop a fully density-dependent age-structured model to project abundances for both anadromous and resident sockeye. The model considers trophic interactions due to nutrient variation and the density dependent consequences for smolting and adult returns. Moreover, it asks how each life history type will persist if a hatchery were used to promote anadromous sockeye through artificial selection. We show hatchery supplementation is unlikely to significantly impact anadromous or resident sockeye, although there is substantial prediction uncertainty suggesting in projections. Our study suggests that providing passage for previous land-locked anadromous populations will lead to the return of anadromous fish in the short-term, but long-term prospects are far from certain. âThe 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