Hatchery-reared salmonids often contain proportionally greater amounts of body lipid (storage fat) and proportionally lesser amounts of body protein (muscle) and ash (bone) than do their wild counterparts of equal size. The effect of body composition on postrelease survival and subsequent return of mature adults is presently unknown. High lipid deposits may benefit the fish by providing reserve energy during adaptation to the wild, or may hinder the fish by delaying
transformation and downstream migration. Compositional differences between hatchery and wild fish may be attributed to various factors, including altered environment, feeding rate, level of exercise, or diet. Diets presently fed to chinook salmon (Oncorhynchus tshawytscha) fingerlings are formulated to produce maximum growth, and they contain higher levels of lipid in proportion to protein than would be found in natural prey. Our objective was to determine what
relation exists between dietary protein level and body composition in cultured chinook salmon.
