Abstract

This study conducted hybridizations between cold water Haliotis discus hannai and warm water Haliotis discus discus to produce both hybrid and pure hatchery stock and then compared growth and survival between the hybrid and pure seeds which were reared in indoor tanks and then seawater cages. A 250 day long culture in indoor tanks showed the highest growth in the hybrid H. discus hannai ♀ ${\times}$ H. discus discus ♂, which was followed by the pure H. discus hannai ♀ ${\times}$ H. discus hannai ♂. After the 250 day long culture in tanks, seeds with about 34 mm shell length were selected from the tanks and transferred to seawater cages to be reared for another 950 days. The sea cage culture also showed the highest growth in the hybrid H. discus hannai ♀ ${\times}$ H. discus discus ♂ like indoor culture. Survival rate of the pure H. discus hannai ♀ ${\times}$ H. discus hannai ♂, the hybrid H. discus hannai ♀ ${\times}$ H. discus discus ♂, the hybrid H. discus discus ♀ ${\times}$ H. discus hannai ♂, and the pure H. discus discus ♀ ${\times}$ H. discus discus ♂ during the 950 day cage culture was $38.63{\pm}0.02%$, $39.63{\pm}0.01%$, $31.25{\pm}0.02%$ and $24.25{\pm}0.05%$, respectively, indicating the hybrid H. discus hannai ♀ ${\times}$ H. discus discus ♂ having the highest Survival rate. In conclusion, the comparison of growth and mortality between the hybrid and pure seeds reared in land-based tanks and seawater cages demonstrated that the hybrid H. discus hannai ♀ ${\times}$ H. discus discus ♂ performed the best.