Study on distribution of Ovalipes punctatus (crab) in the East China Sea

Based on the data of four seasonal oceanographic censuses in the East China Sea (26°00' - 33°N, 120°00' - 127°E)in 1998 - 1999, this paper discussed the variation of a swimming crab Ovalipes punctatus resources in the East China Sea with mathematical analysis. Results showed that there was clearly seasonal change of resources density of the crab that was the highest in spring(2 076 ind·km-2and 65.00 kg·km-2) ,then summer(395ind·km-2 and 43.71 kg·km-2), winter (643ind·km-2 and 26.27 kg·km-2) and the lowest in autunm(7ind·km-2and 0.36 kg·km-2). The yield of O. punctatus, whose dominance and occurrence frequency were higher than other waters of the East China Sea, was equal to 50% of total crab in weight at northern offshore water area where the resources of 0. punctatus are mainly distributed in spring and winter. The central fishing ground, which was the greatest ground in the East China Sea, lay in water area of 31°30'-33°00'N, 122°30' - 124°00'E where the crowd of the crab is mainly composed in spawn group in spring. Besides this, other two high abundant fishing ground of the crab lay in 26°00' - 26°30'N, 122°00' - 123°00'E and 30°00' - 31°00'N, 124°30' - 126°30'E. They are both potential fishing ground of the crab in East China Sea because their resources were not exploited fully by now. The fishing season of the crab was from March to June in spring. Because draw net and crab cage were used widely in crab fishing, proper net mesh should be adopted to protect supplement group of the crab in the fishing. Summer was also a good fishing season like spring because the crab resources had greatest individual size, highest ecomonical value and amount of the crab resources in this fishing season. Though it can adapt to wide temperature and salinity as an eurythermic and euryhaline species the crab showed a character of temperature-water species and tended to distribute in low salinity waters. Ovalipes punctatus was a most imporant species in crab community in the East China Sea because the change of amount would affect total resources of crab remarkably in this water area.