Effects of three incubation substrates on emergent fry of sockeye salmon (Oncorhynchus nerka)

Abstract

Many aquaculture projects are substituting plastic for gravel as a rearing substrate for salmonid alevins. The quality of emerging fry reared on different substrates (natural gravels, plastics, and human-selected gravels) has not been compared. Sockeye salmon (Oncorhynchus nerka) were incubated in separate stream-side incubators containing rounded river gravel, fractured/crushed river gravel, and plastic Intalox saddles. Survival, length, weight, and condition of development, were similar for fry from all incubators, regardless of substrate. Median emergence timing was significantly different (P<0.05) for fry emerging from round gravel, angular gravel, and Intalox plastic saddles (842, 851, and 857 degree—days respectively). Natural fry had a median emergence time of 802 degree-days. Survival of incubator fry was four times that of fry in natural habitat. Fry reared in stream-side incubators were shorter, weighed less, and emerged at an earlier stage of development than fry reared naturally.