Migratory patterns of sockeye salmon (Oncorhynchus nerka) smolts in the Strait of Georgia, British Columbia, as determined by analysis of parasite assemblages

Abstract

Sockeye salmon smolts from the Fraser River system, migrating northward through the Strait of Georgia towards the Pacific Ocean, follow either an eastern route by immediately travelling northward upon leaving the Fraser River estuary or a western route by first crossing the Strait of Georgia towards Vancouver Island and then moving northward diagonally across the Strait of Georgia to join smolts migrating along the mainland shore. We used variations in parasite assemblages among Fraser River and Lake Washington sockeye smolt stocks and a maximum-likelihood mixture model to estimate the stock composition of the smolts along the two migratory routes. The results showed that most Fraser River sockeye smolts migrate northward via both the eastern and western routes through the Strait of Georgia, indicating that there is no stock specific route selection. Lake Washington smolts were more prevalent along the western route and we suggest that these smolts are transported westward when attempting to cross the Fraser River plume.