Sex Differences in Spawning Behavior and Body Size Among Wild and Hatchery Pink and Chum Salmon in Prince William Sound, Alaska

Variation in the evolutionary ecology of wild and hatchery-produced salmonids is generally not well understood. Here, we analyze data collected as part of a large, on-going study by the Alaska Department of Fish and Game on interactions between wild and hatchery Pink (Oncorhynchus gorbuscha) and Chum (O. keta) Salmon in Prince William Sound. This multi-year field study is based on the fact that adult wild and hatchery fish that return to spawn can be differentiated by the absence or presence of otolith thermal marks that reflect a specific hatchery of origin. We rely on field data collected during 2013 and 2014 for our analyses. First, we simply examine sex-specific differences in return rates of wild versus hatchery Pink and Chum Salmon to spawning streams, and ask if these differences vary across management districts in Prince William Sound. Secondly, we examine sex-specific differences in body size and relationships with the seasonal timing of spawning between wild and hatchery ecotypes. Our analyses are a first effort to understand factors that might be important in potential differential reproductive success of wild and hatchery Pink and Chum Salmon in Alaska.