Mixed-Stock Analysis of Yukon River Chum Salmon: Application and Validation in a Complex Fishery

Abstract

Yukon River chum salmon Oncorhynchus keta are managed under the Pacific Salmon Treaty (PST), which requires conservation and equitable sharing of this fishery resource by the USA and Canada. Fall chum salmon are of special concern because they spawn in both the United States and Canada, and the focus of the PST is on Canadian-origin salmon. Yukon River chum salmon were assayed for genetic variation at 22 microsatellite loci to establish a baseline for mixed-stock analysis (MSA) applications to assist in addressing conservation and allocation issues. The baseline has been applied yearly to estimate the stock composition of Yukon River fall chum salmon from samples collected in the Pilot Station test fishery. Accuracies in MSA simulations for 12 of 14 management regions exceeded 90%, with a range of 80–98%, for the 12 most informative loci. Stock composition estimates were within 10% of the actual proportions in a known-origin mixture analysis. Stock-specific abundance estimates, which were derived from combining the estimates of genetic stock composition of Pilot Station test fishery harvests with sonar abundance estimates, were concordant with upriver escapement data. The combination of genetic MSA using the baseline developed in this study and sonar abundance provides a viable tool for assessing stock strength and assisting managers in regulating fisheries to maintain the productivity and evolutionary potential of Yukon River chum salmon.