The consumption of euphausiids by the pelagic fish community off southwestern Vancouver Island, British Columbia

Abstract

The consumption of adult euphausiids was estimated for the seven most abundant fish species found on the continental shelf off southwestern Vancouver Island, British Columbia, Canada. Empirical data on fish feeding rates, diets and biomass were used to estimate euphausiid consumption in August for each year from 1985 to 1997. The fish community in August was estimated to consume an average 297 kt of euphausiids (124 t km-2). Pacific hake (Merluccius productus) and Pacific herring (Clupea harengus) accounted for 60% and 30%, respectively, of the total euphausiids consumed by fish. The total estimated consumption of euphausiids per tonne of fish averaged 0.93, and there was no significant trend in the time series. In addition, there was no significant relationship between the total fish community consumption or euphausiids consumed per tonne of fish and euphausiid biomass, and there was no change in the fraction of euphausiids in the diet of small or large Pacific hake. Thus, it appears that predation pressure from the pelagic fish community was relatively constant and not responsible for the apparent fivefold decline in adult euphausiid biomass observed in the 1990s.