Affiliation: | Division of Science Education, Miyagi University of Education, Sendai 980–0845 Japan; School of Fisheries Sciences, Kitusato University, Ofmato, Iwate 022-0101 Japan; Nikko Branch, National Research Institute of Aquaculture, Nikko, Tochigi 321-1661 Japan; Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo 113-8657 Japan |