1Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba 277-8564, 2Hokkaido Research Organization, Kushiro Fisheries Research Institute, Kushiro, Hokkaido 085-0024, 3Hokkaido Research Organization, Hokkaido Central Fisheries Experiment Station, Yoichi, Hokkaido 046-8555, 4Kagawa Prefectural Fisheries Experimental Station, Takamatsu, Kagawa 761-0111, 5National Research Institute of Fisheries Science, Fisheries Research Agency, Yokohama, Kanagawa 236-8648, 6Seikai National Fisheries Research Institute, Taira-machi, Nagasaki 851-2213, 7Graduate School of Agricultural Science, Tohoku University, Sendai, Miyagi 981-8555, 8Field Science Education and Research Center, Kyoto University, Sakyo, Kyoto 606-8502, Japan
Reproductive traits of Japanese anchovy Engraulis japonicus were compared among the subtropical, subarctic, and inland sea areas around Japan. Adult anchovy in the subarctic areas were large in body size (standard length SL>120 mm, body weight BW>20 g) and had gonad-somatic index (GSI=GW×102/BW) greater than 7.0. Their total (per female) and specific (per 1 g BW) fecundity, estimated by the number of advanced oocytes in the ovary, were 18000 and 700, respectively. Their spawning activity was detected in June and July. In the subtropical sea areas, on the other hand, adults with advanced oocytes occurred all year round except for December and January. Their body and gonad sizes were large in spring (SL>120 mm, BW>20 g, GSI>5.0) with high total (>4500) and specific (>300) fecundities, but decreased in summer and autumn to as small as SL<60 mm and total and specific fecundity of 50 and 30, respectively. These diverse biological traits suggested that the reproductive ecology of anchovy is adaptive to local sea areas around Japan.