Effect of ascidian (Halocynthia roretzi, Drasche 1884) tunics carotenoids on enhancing growth and muscle coloring of sea-reared rainbow trout (Oncorhynchus mykiss, Walbaum 1792)

AbstractA 120days trial was conducted to investigate the effect of sea squirt (Halocynthia roretzi, Drasche 1884) tunic’s carotenoid to sea-reared rainbow trout (Oncorhynchus mykiss, Walbaum 1792) growth and muscle color. Sea-rearing was done at Tongyeong sea area, Korea. Three dietary treatments, namely control (C), CT, and AT, were administered to 6 groups of fish (n=490-520). C was given basal diet which has contained 40mgkg−1 of astaxanthin. A further inclusion of 10mgkg−1 canthaxanthin was added to diet of CT, while AT’s feed was supplemented with 10mgkg−1 H. roretzi tunics carotenoids extract. The result revealed that AT has the highest final weight (1119.2±82.4g) compare to those of C (881.0±121.2g) and CT (1068.2±4.3g). The specific growth rate (SGR) of AT (1.0±0.07%/day) was significantly higher than C (0.7±0.22%/day) and CT (0.7±0.25%/day) while the feed conversion ratio (FCR) were 1.5±0.6, 1.4±0.6, and 1.2±0.1 for C, CT and AT respectively. The hepatosomatic index (HSI) and Viscerosomatic index (VSI) of all groups showed no significant difference (p>0.05). The muscle color was also positively affected by the treatments, CT and AT were significantly different from C (p<005). The initial muscle color score was 1.7±0.0 and the final scores were 3.4±0.2, 5.6±0.1, and 5.7±0.0 for C, CT, and AT respectively. Moreover, muscle carotenoids content of AT (8.5±0.2mgkg−1) was significantly higher (p