1. Department of Fisheries Science, Faculty of Agriculture, Kyushu University, 6-10-1 Hakozaki, Fukuoka 812-81, Japan, Department of Applied Biological Sciences, Faculty of Agriculture, Saga University, 1 Honjo, Saga 840, Japan, and Department of Food Science and Technology, National Fisheries University, 2-7-1 Nagatahonmachi, Yamaguchi 759-65, Japan