Food consumption and growth of the juvenile sea urchin Strongylocentrotus intermedius

Seasonal changes in food intake and digestion, and growth of the juvenile sea urchin Strongylocentrotus intermedius feeding on the large brown algae Sargassum confusum and Laminaria religiosa were studied during a rearing experiment. The food intake and the proportion of food digested were higher for sargasso than for kelp during July and October but lower during November and March, when only thalli without main or lateral branches of sargasso were consumed, resulting in a lower growth rate. The feed conversion efficiency for sargasso was higher during May and June, and lower during August and October, than that for kelp. However, the digestibility of both algae was inversely related to the feed conversion efficiency. It is considered that changes in digestibility and feed conversion efficiency are caused by interspecific differences and seasonal variations in nutrient levels.