SEASONAL-CHANGES IN FEEDING-ACTIVITY OF T HE SEA-URCHIN STRONGYLOCENTROTUS-NUDUS IN OSHORO BAY, SOUTHWESTERN KOKKAIDO

Bimonthly observations of feeding activity of the sea urchin Strongylo centroius nudus transplanted from coralline flats were carried out bet ween September 1989 through July 1990 by providing the kelp Laminaria religiosa in Oshoro Bay, the Sea of Japan coast of Kokkaido, Japan. Fe eding activity of the sea urchins varied chiefly with their annual rep roductive cycle. Feeding activity was high in May when their gonads we re in the growing stage, while feeding activity was low in September w hen gonads were in the pre-mature. The sea urchins could not feed in w inter due to low temperature (ca. 5 degrees C) and high wave action. I t was suggested that the sea urchins on coralline flats should be tran splanted to calm inlets before June and provided with the kelps as a d iet in order to promote the growth of their gonads in short-period.