Fishery Selection on Alaskan Sockeye Salmon: Are We Catching the Big Ones and Is There Potential for Evolutionary Change?

Abstract

Bristol Bay, Alaska, USA, produces some of the most abundant and biologically diverse sockeye salmon (Oncorhynchus nerka) runs in the world, many of which have been heavily fished by gillnet fisheries for over 100 years. Quantification of fishery selection on age and size at maturation over long time periods is essential to understand evolutionary consequences on stock demographics and sustainable fishery management. We performed these quantifications for multiple fishing districts from 1946-2008 and evaluated how different management strategies affected fishery selection in different areas. Analyses revealed that larger than average fish were caught in most years, selection differed significantly between males and females, and patterns of selectivity differed based on harvest levels and fishing gear used. Proving evolutionary change associated with such selection is difficult, but we were able to correlate long term shifts in length at age with fishery selection across districts. We discuss how to minimize evolutionary changes in age and size at maturity due to fishery selection and conserve our valuable sockeye salmon resources.