A dynamic model describing ecosystem-level changes in the Strait of Georgia from 1960 to 2010

We developed an ecosystem model of the Strait of Georgia which emulates biomass and mortality changes between 1960 and 2009 to study ecosystem mechanisms governing dynamics in fished species and marine mammals. The model uses hindcast annual variation in bottom-up production, fisheries catches and predator-prey dynamics to simulate observed changes in fish, mammal and bird populations in the Strait of Georgia. This model emulates the timing and magnitude of historic changes in biomass and mortality of Coho and Chinook salmon as well as other major species like Pacific herring, orcas, harbour seals, lingcod, spiny dogfish and marine birds. Simulated production trends indicate the Strait of Georgia had relatively high production from the mid-1970s to late 1980s and entered a lower production regime in the early 1990s that has persisted to 2009. The simulations also indicate that the mean trophic level of vertebrates declined over the period 1990 to 2009. This model provides a tool to evaluate potential ecosystem changes in the Strait of Georgia.