Simulated and observed response of the southwest Vancouver Island pelagic ecosystem to oceanic conditions in the 1990s

In this paper, we discuss changes in the ocean climate around La Perouse Ba nk off southwestern Vancouver Island, British Columbia, and its influence o n the functioning of the pelagic ecosystem. We compare results of a one-dim ensional simulation model of plankton and fish production and biomass dynam ics with empirical data collected in the 1990s. Comparisons of simulation r esults with empirical data indicate that the La Perouse model can account f or relative interannual changes in copepod biomass, euphausiid biomass and production, the consumption of Pacific herring (Clupea pallasi) by Pacific hake (Merluccius productus), and the growth condition factor of Pacific hak e. The model is less successful at capturing changes in spring diatom bioma ss, the proportion of euphausiids in the Pacific hake diet, and interannual variability in the Pacific herring condition factor. A measure of overall model performance suggests that the La Perouse ecosystem model performs equ ally well in both strong and weak upwelling periods. The La Perouse ecosyst em model has been used to generate an annual index of net phytoplankton and macrozooplankton production for the coastal upwelling region off southwest ern Vancouver Island from 1967 to 1998.