Bathymetric distribution of beni-zuwai crab Chionoecetes japonicus in the northern part of the Sea of Japan
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ORIGINAL ARTICLE
Biology
Bathymetric distribution of beni-zuwai crab Chionoecetes japonicus in the northern part of the Sea of Japan Ikuko Yosho Æ Taro Hirose Æ Shigeru Shirai
Received: 9 February 2009 / Accepted: 17 August 2009 / Published online: 7 October 2009 Ó The Japanese Society of Fisheries Science 2009
Abstract Surveys of beni-zuwai crab were conducted to clarify the bathymetric distribution and fecundity of benizuwai crab populations without the effects of bias due to fisheries. The results were compared with previous ones obtained at the heavily exploited Yamato Bank. Two sites in the northern part of the Sea of Japan, off southwest Hokkaido (200–2500 m deep) and West-Tsugaru Basin (300–1900 m deep), both of which are experiencing low exploitation levels, were surveyed in August to September, 2007. There was an abundance of morphologically immature crabs of both sexes in the depth range 1800–2100 m, and a few occurred at depths [2200 m. Immature crabs of \40 mm carapace width were found to migrate downslope to depths of 1800–2100 m and then to migrate upslope during molting for males and after maturity molting for females. Although data were lacking for depths [2000 m at the West-Tsugaru Basin, these relationships were significant for the pooled data of both localities, and they were similar to the results at the Yamato Bank. Clutch fullness of ovigerous females was negatively correlated with depth, which indicates that the low clutch fullness was not induced by fisheries, although the similar phenomenon observed at the Yamato Bank had previously been considered to be due to fishery effects.
I. Yosho (&) T. Hirose Japan Sea National Fisheries Research Institute, Fisheries Research Agency Japan, 1-5939-22 Suido-cho, Chuo-ku, Niigata City, Niigata 951-8121, Japan e-mail: [email protected] S. Shirai Faculty of Bioindustry, Tokyo University of Agriculture, 196 Yasaka, Abashiri, Hokkaido 099-2493, Japan
Keywords Beni-zuwai crab Distribution Migration The Sea of Japan Unfished population
Introduction The importance of protecting deep-sea species and habitats has recently been highlighted by the Food and Agriculture Organization of the United Nations (FAO; International Guidelines on Deep Sea Fisheries, report no. 855, FAO, Rome). To date, few countries have developed policies and plans for managing deep-sea fisheries, even those in their own waters. However, many deepwater fish species are thought to have a low resilience to intensive fishing due to their slow growth, late maturity and prolonged reproductive cycles. Beni-zuwai crab Chionoecetes japonicus is one such deepwater species, inhabiting bottoms at depths of 500– 2700 m deep in the Sea of Japan where the temperature \0.5°C [1]. It has a biennial reproductive cycle [2, 3] that is longer than that of the snow crab C. opilio inhabiting the neighboring but shallower and warmer bottoms at depths of 200–500 m. Beni-zuwai crab fisheries started in the 1960s in the Sea of Japan, and total landings along Honshu increased due to the higher fishing
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