Prey selectivity and diet overlap in juvenile pink, chum and sockeye salmon in the Gulf of Alaska and Prince William Sound, Alaska

Abstract

Pink, chum and sockeye salmon are the three most commercially important Pacific salmon. As juveniles, they co-occur in coastal waters of Alaska. To assess the potential for competition among juveniles of these species, I examined their diets in Prince William Sound and in nearby continental shelf waters in the summer and fall of 2001 and quantified surface zooplankton at the same sampling stations. I estimated diet diversity, diet overlap and prey selectivity of the three species. A large proportion of gelatinous prey, especially larvaceans, characterized juvenile chum salmon diet. A pteropod, Limacina sp., was an important prey for juvenile pink and sockeye salmon. Juvenile pink and sockeye salmon diets consisted of a wider variety of prey than those of chum salmon; they also had a higher prey overlap with each other than with chum salmon. The three species showed similar trends in selectivity in Prince William Sound and in shelf waters. These results suggest that there is a higher probability of competition between juvenile pink and sockeye salmon than between either juvenile pink or sockeye salmon and chum salmon.