Differences in Performance of Naturally and Artificially Propagated Sockeye Salmon Migrant Fry, as Measured with Swimming and Predation Tests

Abstract

Two methods of performance testing were developed to measure differences in stamina in four groups of sockeye migrant fry, all of the Lakelse Lake (Skeena River, B.C.) stock. The four groups differed only in methods of incubation: one group was naturally propagated, the other three artificially. The results of the swimming performance tests and the vulnerability to predation tests agree closely, and analysis shows that the key factor responsible for differences in performance is size of the fish. Ranked in decreasing order of performance these four groups rate as follows: naturally propagated fish, fish incubated in gravel from time of hatching, fish incubated in gravel only for the last few weeks as premigrants, and fish that spent their entire incubation period without gravel in hatchery baskets. Independent of size is the influence of condition (K-factor) of the fish, optimum performance occurring at the time of almost complete yolk absorption. Of the two methods the swimming performance test was found to be more sensitive and is recommended as a tool for comparative "quality testing" of fish stocks.