Size Selective Predation Among Juvenile Salmonid Fishes in a British Columbia Inlet

• Published in: Journal of the Fisheries Research Board of Canada
• Main Author: Parker, Robert R.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1971
• Subjects: Keta; Oncorhynchus gorbuscha
• Online Access: http://dx.doi.org/10.1139/f71-231; http://www.nrcresearchpress.com/doi/pdf/10.1139/f71-231

Field observations suggest early sea mortality of pink (Oncorhynchus gorbuscha) and chum (O. keta) salmon fry is largely due to predation by juvenile coho (O. kisutch) salmon. A series of experiments demonstrates a strong bias toward the smaller individuals of the prey population. This results in an apparent growth rate 0.3–0.5% per day due to the biased mortality alone. With a high innate growth rate [Formula: see text], the prey are shown to "outgrow" the predator [Formula: see text], and hence become unavailable. Chums are shown to have an advantage over pinks through slightly earlier entry into the estuary and a larger initial size. The mechanism of selection used by the predator is not known from this study.