COMMERCIAL TROLL FISHING VESSEL DISTRIBUTION OFF VANCOUVER ISLAND DURING JULY 1988 - RELATION TO OBSERVED PHYSICAL OCEANOGRAPHY

We compare distributions of salmon troll fishing vessels obtained usin g navigational radar observations off southwestern Vancouver Island in mid-July 1988 with the circulation and water property structure deriv ed from concurrent oceanic measurements. Results support the hypothesi s that vessels aggregate in clusters within the transition zone formed between the upwelling-induced shelf-break current and buoyancy-driven Vancouver Island coastal current. Dense clusters of vessels within th is zone appear to be coincident with mesoscale (10 km) circulation fea tures embedded in the large-scale (100 km) coastal upwelling regime. I n all instances, the association of vessel aggregations and oceanic ci rculation illustrates a response of the salmon to local oceanographic conditions. The circulation features presumably correspond to upwellin g-enriched regions with high food organism densities that attract aggr egations of salmon.