The effects of different stocking densities on the growth and survival rate of the abalone, Haliotis discus hannai, were investigated in marine net cage for two years. Stocking density was set 15, 30, 45 and 60 percentage (= per.) /m2 with share to cross-sectional area per shelter. The primary rearing period (PRP) and the secondary rearing period (SRP) were conducted by a year. One year mean water temperature of PRP and SRS showed the difference about 2℃. In the growth (initial mean shell length of abalone : 36.14 ± 2.28 mm) of PRP, the absolute growth rate (ARG), daily growth rate (DGR) and specific growth rate (SGR) of the 15 per./m2 were higher than those of density groups (P < 0.05). Survival rates of all density groups were showed no significant difference. In the growth (mean shell length of abalone : 55.26 ± 6.93 mm) of SRP, ARG, DGR and SGR of stocking density groups showed no significant difference except for 45 per./m2 density group. Survival rate in the low-density (15, 30 per./m2) was more than 70%, and those of the high-density (45, 60 per./m2) were less than 31% and 9%, respectively. These results showed that the appropriate stocking density for 15 per./m2 was seven hundred fifty number per one net cage (2.4 × 2.4 m), during PRP using 3-4 cm abalone in length. Also for the secondary rearing period, the optimal stocking density (shell length 5-6 cm of abalone) consider with the economical efficiency was determined to be 30 per./m2, resulting the productivity improved.
