Adult Production of Chinook Salmon Reared at Different Densities and Released as Two Smolt Sizes

Abstract

Abstract Chinook salmon (Oncorhynchus tshawytscha) were reared at densities of 6.6–24.3 kg/ m3 and released as small (9.7–10.3 g) or large (28.2–31.8 g) smolts to determine the effects of fish size at release and rearing density on postrelease growth and adult return rate. Density did not affect survival during rearing, but mean weights for both size-classes were significantly lower at the highest rearing densities (P < 0.05). Density and size at release affected adult return rates, which were lower for fish reared at high densities for both size-classes. However, the increased number of smolts produced at higher densities compensated for the reduced return rates by yielding a higher number of returning adults per unit volume of rearing space. The estimated costs for each adult produced were US$11.10–12.00 for small smolts and $13.10–23.80 for large smolts. The lowest costs were projected at the second-highest density (18.6 kg/m3) for small smolts and at the highest density (20.3 kg/m3) for large smolts.