Emergence Trap and Holding Bottle for the Capture of Salmonid Fry in Streams

Abstract

A 0.12-m 2 fry emergence trap was constructed of rigid steel strip, plumber's tape, and nylon netting. A holding bottle was fashioned from a polyethylene screw cap bottle and plastic funnel. The trap was inexpensive, durable, and effective in a wide range of current velocities. The method proved effective in estimating egg-to-fry survival rates for kokanee (Oncorhynchus nerka) in various sediment mixtures. Egg-to-fry survival varied from 0 to 52%, and was negatively correlated to percent fines (r = 0.91; P < 0.01). The emergence period indicated by the trap catches in McDonald Creek agreed closely with the period indicated by drift-net sampling. Fry mortality in the holding bottle was almost nil if the trap was checked at least once a week.