The effect of oil-extracted astaxanthin from the red crab or langostilla (Pleuroncodes planipes) on the growth and pigmentation of forty five rainbow trouts (Oncorhynchus mykiss) was investigated by feeding a test diet supplemented with 75 mg/kg of astaxanthin during six weeks and compared with a control diet. The oil-extraction process of the pigment is described. Weight, flesh astaxanthin concentration, and color (L*, a*, b*) of the flesh were measured at 0, 3, and 6 weeks. No apparent effect of astaxanthin supplementation was observed on fish development. In spite of the low free astaxanthin amount in the diet (8%), an acceptable carotenoid concentration in the flesh (3.60 +/- 0.78 mg/kg, w/w), and a red hue (H(ab)o = 44.13 +/- 2.36) were obtained at the end of the study. The red hue was strongly correlated with the carotenoid concentration (r = 0.98).