江苏阳澄湖螺类群落的空间分布格局

2008年1月～2009年10月对江苏阳澄湖螺类群落结构进行了季节调查研究。共采集到螺类4科5属6种，优势种为铜锈环棱螺，次优种为长角涵螺。阳澄湖螺类平均密度为220±47 ind./m2，平均生物量为2331±469 g/m2，螺类密度和生物量在年际和季节间均无明显差异，但群落结构存在显著的空间变化，密度在东湖区和中华绒螯蟹围网养殖区较大、西湖区最小，生物量围网养殖区最高、西湖区最低；铜锈环棱螺密度围网养殖区最高、西湖区最低，长角涵螺密度东湖区最高、围网养殖区次之、入湖河流及其它湖区极低。中华绒螯蟹养殖未导致围网养殖区螺类数量下降，螺类（主要是铜锈环棱螺）的投放可能是该区螺类密度、生物量及铜锈环棱螺所占比例较高的主要原因之一。逐步回归分析表明，水深是影响螺类群落整体密度和生物量空间分布差异的主要因子；典型对应分析（CCA）表明，铜锈环棱螺主要分布在叶绿素a较高的水域，而长角涵螺和纹沼螺则主要分布在透明度较大的地方

SPATIAL DISTRIBUTION OF SNAIL(GASTROPOD)COMMUNITY IN YANGCHENG LAKE,JIANGSU PROVINCE,CHINA

During the seasonal investigation on the snail community in the tributaries(TRIB),western basin(WB),middle basin(MB),eastern basin(EB),and culturing enclosures of Chinese mitten crab(Eriocheir sinensis)(CEES)of Yangcheng Lake,Jiangsu province from Jan.2008 to Oct.2009,six snail species belonging to 5 genus,4 families were recorded,in which Bellamya aeruginosa was predominant,and Alocinma longicornis subdominant.The mean density and biomass of snails in Yangcheng Lake were 22.0±4.7 ind./m2 and 23.31±4.69 g/m2,respectively,both of which didn’t display seasonal and yearly variations,but differed significantly spatially.The relatively larger density occurred in CEES and EB and the least in WB;the highest biomass was found in CEES,and the lowest in EB.The highest abundance of B.aeruginosa appeared in CEES and the lowest in WB,while EB had the highest abundance of A.longicornis followed by CEES,and TRIB and the other two basins possessed the extremely low values.The highest density and biomass of snails,specially of B.aeruginosa,in CEES suggested that the enclosure culturing of E.sinensis couldn’t led to the decline of density and biomass of the snail communities,and this fact would be explained by throw-in of snails(mainly B.aeruginosa)towards the culturing enclosures of E.sinensis.The stepwise regression analysis showed that among physical and chemical environmental factors only water depth could be used to explain the spatial variations of snail density and biomass,and the canonical correspondence analysis(CCA) indicated that B.aeruginosa tended to occur at sites with higher concentration of chlorophyll a,while A.longicornis and Parafossarulus striatulus at sites with larger transparency.