Swiftsure and amphitrite british columbia canada banks juvenile salmon survey september 25 29 october 9 13 november 16 18 and november 23 25 1987
Olsen, N.H.; Morris, J.F.T.; Healey, M.C.
Canadian Technical Report of Fisheries and Aquatic Sciences 1615: I-IV, 1-25
1988
Document Number: 381678
Aggregations of juvenile chinook (Oncorhynchus tshawytscha) and coho (O. kisutch) salmon are known to exist over Swiftsure and other banks, which lie on the continental shelf off southwest Vancouver Island. These aggregations are hypothesized to form in response to eddies caused by tidal current rectification. In the spring and fall, respectively, the summer and winter circulation over the continental shelf undergo a transition phase during which eddying and other stable components of shelf circulation break down. We hypothesize that these events cause the dispersal and redistribution of juvenile salmon aggregates. Employing commercial trolling methods, we conducted exploratory surveys on Swiftsure and Amphitrite Banks in September, October, and November of 1987 to obtain data on juvenile abundance, distribution, and size and species compositions before and during the fall transition. This report summarizes the information obtained.