摘要
本文报道1963年4—5月和10—11月两度在东湖101个采样点上进行软体动物定量采集的结果。软体动物计41种,隶10科、20属,其中腹足类的种类多,生物量也大,瓣鳃类则全系小型种类[主要为河蚬(Corbicula fluminea)],个体数及生物量都很低。根据10—11月的调查结果,全湖软体动物平均生物量为30.5克/平方米(平均个体数为134个/平方米),其中以铜锈环稜螺(Bellamya aerginosa)生物量最大(15.5克),其次为纹沼螺(Parafossarudus striatulus)(5.8克)和长角涵螺(Alocinma longicornis)(6.4克),这3种腹足类占全部软体动物生物量的90%以上,是东湖中的优势种类。它们的分布型式属大小不等的核心分布,其实际分布概率,符合P-E 分布的理论概率。环境分析表明铜锈环稜螺的分布主要取决于水深(r=-0.257;d.f.=99;p<0.01);长角涵螺数量的多寡受制于水草的有无(均数比较:d.f.=99时,t′=7.656;t_(0.01)≈2.641);而纹沼螺的分布则与水深有关(r=-0.697;d.f.=99;p<0.01),又与水草的有无有关(平均数比较:d.f.=99时,t′=6.93;t_(0.01)≈2.641)。
By analysing the data of mollusca from quantitative samples taken by a 1/7 M^2hand-grab from 101 sampling positions randomly distributed in Lake Tung-hu dur-ing March-April and October-November 1963,preliminary results concerning someecological aspects of Mollusca in this shallow lake were obtained.They may besummarized as follows:(1) The most abundant forms of Mollusca are the gastropods,among whichAlocinma longicornis,Parafossarulus striatulus and Bellamya aeruginosa are predo-minant.They represented 79% of total molluscan biomass in spring and 91% inautumn. (2) The population structures of predominant species exhibit a definite patchi-ness.The values of ∑((?))~2/x(n-1) as computed from the data of three predo-minant gastropods were all significantly greater than unity.(3) The distributions of population densities of predominant species are cor-related with certain environmental factors.It was found that A.longicornis and P.striatulus were more abundant in localities where aquatic vascular plants were presentwhile B.aeruginosa was plenteous upon sandy bottom.The numerical distributionsof P.striatulus and B.aeruginosa were also shown to be correlated with the waterdepth.(4) The standing crop of Mollusca as a whole in the lake during 1963 was 8.7 g.per M^2 (ca.243 metric tons in whole lake) in spring and 30.5 g.per M^2 (ca.850metric tons in whole lake) in autumn.
