Serum carotenoid concentration changes during sexual maturation in farmed rainbow trout (Oncorhynchus mykiss)

One hundred forty individually tagged rainbow trout (Oncorhynchus mykiss) were fed diets supplemented with astaxanthin (100 mg/kg) or canthaxanthin (80 mg/kg) during sexual maturity. Only 20 subjects were followed to the end of experience. Blood sampling was withdrawn each month to evaluate pigment concentrations. In females a decrease took place 1 month before spawning, whereas in males variations were not so marked. Females had a higher carotenoid concentration than males. Mean serum levels of astaxanthin ranged in female rainbow trout from 2.80 to 3.33 mu g/mL and from 0.67 to 2.32 mu g/mL for canthaxanthin. Serum astaxanthin levels in male trout ranged from 0.99 to 3.28 mu g/mL and for canthaxanthin from 0.78 to 1.28 mu g/mL. Between-subject (V-b) and within-subject (V-s) variations appeared. Serious error can occur when single measurement are used to categorize individuals. Carotenoid levels in the serum of trout during spawning period would not be an adequate indicator for muscle pigmentation.