Promotion of maturation and spawning of sea urchin Hemicentrotus pulcherrimus by regulating water temperature.

The spawning season of the sea urchin Hemicentrotus pulcherrimus in natural ground, Saga area in Japan starts from around December. In mass production of young sea urchin, the warmer season is then more desirable for the larvae culture. In order to collect the eggs three months earlier than natural spawning season, promotion of maturation and of spawning was conducted by regulating water temperature. The sea urchin which had experienced a period of rising temperature to 26°C, either naturally or artificially, could mature and spawn about 45 days after the temperature was again lowered to 15°C. Those cultured at constant temperature of 15°C from May did not mature and died in July. These experiments suggest that by means of the water temperature regulations, mass production of sea urchin can be commenced from October in the warmer season, the optimum period for culturing larvae. Using this method, the mass production of the sea urchin has been successfully conducted in our station since 1987.