Effect of Marine Algae from the Eastern part of Hokkaido and Feeding Period for Gonad Production of the Sea Urchin Strongylocentrotus intermedius

Abstract

The effect of six algae and one sea grass species abundant eastern Hokkaido to the gonad development in the sea urchin Strongylocentrotus intermedius was examined in land-based tank culture. Each diet was fed to the sea urchins of commercial size (> 45 mm in test diameter, n = 5) in flowing seawater of natural temperature for 75 days after two months of starvation. The gonad index (GI) was higher when kelp (Saccharina longissima, Costaria costata and Alaria praelonga) or a green alga (Ulva pertusa) was fed but lower when red algae (Ptilota filicina and Tichocarpus crinitus) or a sea grass (Phyllospadix iwatensis) was fed; T. crinitus never developed gonads. Feeding of stocked diets (dried S. longissima or frozen U. pertusa) resulted in lower GI than indices in the case of feeding each fresh sample. In comparing two feeding periods with four diets (fresh and dried S. longissima, frozen U. pertusa or fresh P. iwatensis), higher GI was obtained in longer culture (249 days from July) than in shorter culture (186 days from September). The taste sampling test showed higher scores in longer culture (highest in fresh S. longissima) expect dried S. longissima, in which bitterness was not improved.