Modelling Pelagic Fish and Plankton Trophodynamics off Southwestern Vancouver Island, British Columbia

Abstract

A trophodynamics model is used to estimate annual plankton and fish production for the southern British Columbia continental shelf during 1985–89. The model describes the feeding interactions among diatoms, copepods, euphausiids, juvenile and adult Pacific herring (Clupea pallasi), Pacific hake (Merluccius productus), chinook salmon (Oncorhynchus tshawytscha), and spiny dogfish (Squalus acanthias) and is forced by empirical seasonal patterns in upwelling, sea surface temperature, and solar radiation. The most important simulation results are that (1) there is an imbalance between fish consumption and euphausiid production during the summer upwelling season, (2) the biomass and arrival timing of migratory hake significantly influence plankton and fish production, and (3) about 11% of the 332 g C∙m−2∙yr−1 annual diatom production is transferred to copepods and euphausiids and 1.0% of the diatom production to fish, while 27.5% of the 11.9 g C∙m−2∙yr−1 euphausiid production is consumed by herring and hake. The high plankton and fish production on the southern British Columbia shelf is comparable with other productive coastal upwelling regions.