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Rapport, 2007

Contrasting space and food use among three species of juvenile Pacific salmon (Oncorhynchus) cohabiting tidal marsh channels of a large estuary

Northcote, Thomas G; Gregory, Robert S; Magnhagen, Carin


Age 0 juvenile chinook Oncorhynchus tshawytscha, chum O. keta, and pink salmon O. gorbuscha, occupy tidal channels of inner estuarine marsh habitat of the Fraser River for up to several months of their spring seaward migration; although pink are generally only observed in odd-numbered years. We investigated the spatial, temporal, and dietary interactions of these species from February to June during 1986 to 1989. Peak percent occurrence of pink and chum in trap net catches occurred during March to early May, whereas chinook salmon juveniles dominated catches in late May and June. Spatial distribution within tidal channels was species-specific. Mid-channel trawl catches of all three species were significantly lower near the bottom than near the surface. Most pink salmon were caught near surface in the centre of channels, whereas chum and chinook were most abundant within 1.5 m of the channel banks. Diet of all three species included most potential prey sampled by plankton pump, benthic cores, and visual observation of surface drift. Diet overlap by prey volume (Schoener Index) was highest between chinook and chum salmon (90%), and low between pink and the other two species (chum 32%, chinook 30%). Temporal, spatial, and dietary patterns among the cohabiting species were consistent with minimization of potential competition during their estuarine residency period

Publicerad i

Canadian Technical Report of Fisheries and Aquatic Sciences
2007, nummer: 2759
Utgivare: Department of Fisheries and Oceans, Canada