MUSCLE PIGMENTATION AND PLASMA-CONCENTRATIONS OF ASTAXANTHIN IN RAINBOW-TROUT, CHINOOK SALMON, AND ATLANTIC SALMON IN RESPONSE TO DIFFERENTDIETARY LEVELS OF ASTAXANTHIN

Pigmentation development was studied in rainbow trout Oncorhynchus myk iss, chinook salmon O. tshawytscha, and Atlantic salmon Salmo salar fe d similar practical diets supplemented with 40, 70, or 100 mg astaxant hin/kg of diet. The initial mean body weights of the respective specie s were 158, 198, and 191 g. The rainbow trout were reared in freshwate r at 6.0-11.3 degrees C, the chinook salmon in seawater at 8.8-14.4 de grees C, and the Atlantic salmon in seawater at 7.1-12.7 degrees C. Th e response of flesh pigmentation to dietary pigment was most rapid in rainbow trout and slowest in Atlantic salmon. Chinook salmon showed th e greatest variation in response to the different dietary concentratio ns of astaxanthin, followed by rainbow trout and Atlantic salmon. In b oth rainbow trout and Atlantic salmon, pigmentation was most intense i n the distal section and decreased anteriorly. In chinook salmon, pigm entation was most intense in the midsection, followed by the anterior section and then the distal section. Postprandial plasma concentration s of astaxanthin did not fully explain the differences among the speci es in the rare of tissue accumulation of pigment, especially when the diet contained a high concentration of astaxanthin.