We propose to enhance our understanding of the impact of predation and fisheries on Chinook salmon by developing focused ecosystem models that capture interactions between salmon and top predators. These relatively simple models (< 10 species groups) will better quantify consumption by marine mammal predators, will help improve estimates of Chinook salmon natural mortality, and will improve our understanding of other ecosystem interactions, including:
1. Impacts of fisheries adjustments, large-scale environmental changes, or salmon recovery, which may benefit marine mammal populations (particularly killer whales). We will also consider the effects of selective removal of pinnipeds preying on Chinook salmon.
2. Interspecific competition between marine mammal species (killer whales, pinnipeds), and intraspecific competition between resident killer whale populations (the 3 populations in our analysis are thought to consume some of the same salmon stocks as prey (Hilborn et al. 2012, Ward et al. 2013)).
Other benefits of constructing this type of trophic model include refining killer whale bioenergetics models (with Chinook salmon are the primary diet item) and improving our understanding of relative environmental carrying capacities (both at a species and population level).