Influence of episodic upwelling on capelin, Mallotus villosus, and Atlantic cod, Gadus morhua, catches in Newfoundland coastal waters

Wind-induced upwelling in the north-west Atlantic has been hypothesized to influence catch rates of fish by gear fishing at fixed locations. Passive movement to shallow depths during upwelling has been proposed to increase encounter rates of fish with net leaders set at the coast. However, supporting evidence is not conclusive, possibly because fish respond to strong events rather than all events. We investigated whether catch rates of capelin, Mallotus villosus, and Atlantic cod, Gadus morhua, were related to the strength of upwelling, as measured by the rates of water temperature change, or to stage of upwelling. Capelin trap catches were positively related to increases in water temperature, representing the relaxation phase. This result was due primarily to increases in catch after strong (> 4 degrees C change) rather than after typical (< 4 degrees C change) upwelling events. Cod trap catches were not related to upwelling strength but did increase 1-2 days after typical events. The data suggest that upwelling increases capelin movement, while the return of warmer surface water after an upwelling event increases cod movement.