Variable Effects of Biological and Environmental Processes on Coho Salmon Marine Survival in Southeast Alaska

Abstract Correlation analyses, linear regression models, and multistock mixed effects models were used to examine the relationships between coho salmon Oncorhynchus kisutch marine survival and six biological and environmental covariates across 14 southeast Alaska (SEAK) stocks. A primary focus of the study was to investigate the influence of pink salmon O. gorbuscha and chum salmon O. keta fry abundances on coho salmon marine survival. The coho salmon stocks exhibited strong covariation; 88 of the 91 pairwise comparisons among the coho salmon stocks covaried positively and 54 of them were significant (P < 0.05). Only one of the covariates, the North Pacific index, which is a measure of the Aleutian low pressure zone, had consistent relationships (positive) across all 14 stocks. The other covariates, including freshwater discharge, the Pacific decadal oscillation, sea-surface temperature, and two indices of pink salmon and chum salmon fry abundances, all had inconsistent relationships with marine survival....