Aquaculture of the sea urchin (Strongylocentrotus nudus) transplanted from coralline flats in Hokkaido, Japan

To establish aquaculture of the sea urchin Strongylocentrotus nudus on coralline flats where no commercial harvest had been previously obtained, a field experiment on gonadal growth was carried out in a dredged area at Matsumae in southern Hokkaido from October 1988 to March 1989. S. nudus taken from coralline flats and fed on the flesh of the fish Pacific saury Cololabis saira and arabesque greenling Pleurogrammus azonus from October to January showed markedly enhanced gonadal growth. The gonadal moisture and glycogen contents increased and decreased, respectively, and the gonadal whiteness and chroma increased and decreased, respectively. However, all these parameters, excluding the gonadal whiteness, improved after changing the diet to the brown algae Laminaria japonica and Undaria pinnatifida from February to March. I concluded that, after feeding sea urchins on fish, active algal grazing must be maintained at the culture ground to improve the gonadal quality.