Growth of Taiwan abalone Haliotis diversicolor supertexta fed on Gracilaria tenuistipitata and artificial diet in a multiple-tier basket system

Taiwan abalone, Haliotis diversicolor supertexta, juveniles (26.64 +/- 2.30 mm) were placed in 4 sets of 7-basket tiers, 35 abalone in each basket, and reared indoors with running seawater (31-35%) for 395 days. Food was generally given every other day at a rate of 30% and 3% of total body weight for Graciliaria tenuistipitata and artificial diet, respectively. Survival was 64.3-71.4% and 61.4-78.6% in the Gracilaria and artificial diet, respectively. Growth of abalone placed on the top tier was inferior to those placed on the middle and bottom tiers. In the first 33 days, the growth rate of H. diversicolor supertexta fed Gracilaria and the artificial diet was 61-101 and 105-163 mu m/day, respectively. The abalone fed an artificial diet gained twice as much total body weight as those fed Gracilaria after 96 days. The overall growth rate of abalone fed an artificial diet was 24.4, 47.7, and 47.9 mg/day, or 1.8, 2.2, and 2.2 times higher than abalone fed Gracilaria, on the top, middle, and bottom tiers, respectively. The FCR (feed conversion ratio) in dry weight of food was 3.10, 2.68, and 2.76 for the abalone fed an artificial diet, and 4.43, 3.03, and 3.04 for those fed Gracilaria. It is concluded that H. diversicolor supertexta placed in a multiple-tier basket system and fed an artificial diet could grow to market size (>40 mm shell length) in less than half the time in comparison to those fed on Gracilaria.