SEASONAL VARIATIONS OF DIVERSITY OF CRUSTACEANS CAUGHT BY BOTTOM TRAWL IN DAIQUYANG
岱衢洋拖网甲壳动物多样性的季节变化

Based on the data of bottom trawl surveys in Daiquyang during spring (May), summer (August), autumn (November) 2009, and winter (February) 2010, the species diversity of crustaceans was analyzed. The results indicated that a total of 21 crustacean species belonging to 18 genera, 14 families and 2 orders were obtained including 13 species of shrimps, 7 species of crabs and 1 species of squills. Palaemon gravieri was the dominant species in all seasons. Both the biomass and abundance density of crustaceans reached the maximum in autumn, but decreased to the minimum in spring, and the difference in the biomass and number abundance density was significant (P<0.05). By correlation test results, the biomass shown significant quadratic related with average bottom sea salinity (P<0.05). The eurythermal and euryhaline species in the species number, biomass and abundance density all occupied the dominant position, and all dominant species were eurythermal and euryhaline species in the investigated waters. The Margalef richness index (D), Shannon-Wiener diversity index (H′) and Pielou evenness index (J′) in winter was lowest among all the seasons, which shown that the richness, diversity and evenness of crustaceans in winter were all lower. Meanwhile the Margalef richness index (D) and Shannon-Wiener diversity index (H′) in summer and autumn were higher than those in winter and spring in Daiquyang, however, which was contrary in the offshore deep waters, the opposite phenomenon between Daiquyang and offshore deep waters was mainly due to its response to the seasonal variations of bottom sea water temperature.