Bathymetric distribution of beni-zuwai crab <Emphasis Type="Italic">Chionoecetes japonicus</Emphasis> in the northern part of the Sea of Japan |
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Authors: | Ikuko Yosho Taro Hirose Shigeru Shirai |
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Institution: | (1) Japan Sea National Fisheries Research Institute, Fisheries Research Agency Japan, 1-5939-22 Suido-cho, Chuo-ku, Niigata City Niigata, 951-8121, Japan;(2) Faculty of Bioindustry, Tokyo University of Agriculture, 196 Yasaka, Abashiri, Hokkaido 099-2493, Japan |
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Abstract: | Surveys of beni-zuwai crab were conducted to clarify the bathymetric distribution and fecundity of beni-zuwai 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. |
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