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目的 阐明长江下游地区钉螺再次迁入无螺江滩后的钉螺消长和分布变迁规律。方法 采用前瞻性观察的方法 ,每年春季现场调查钉螺分布。结果 每一滩块从局部有螺到全滩有螺平均时间为 4.33年 ,堤外江滩从钉螺迁入到全面有螺的时间需 8年 ,试区从开始有螺到向堤内垦区扩散时间需 7年 ;10年间钉螺面积、钉螺平均密度、有螺框出现率分别增加了 74.97倍、90 .75倍和 10 6倍 ;有螺框出现率呈指数曲线 y=0 .1331e0 .5844 x上升 ;钉螺迁入早期以面积增长为主 ,在面积扩增到一定程度后 ,则转变为以螺口增长为主。结论 螺口数量的增加是钉螺扩散的基础 ,控制钉螺扩散的有效方法是降低螺口的数量
Objective To elucidate the rule of the growth, decline and distribution of Oncomelania snails in the lower reaches of the Yangtze River after they migrated to the Wuluo River again. Methods A prospective observational method was used to investigate the distribution of snails in the spring each year. Results Each Bund block from the local snail to the beach has a snail average time of 4.33 years, embankment beach from snails to snail full time to be 8 years, from the beginning of the trial area snail dike reclamation time required 7 years. The area of snails, the average density of snails and the occurrence rate of snails were increased by 74.97 times, 90.75 times and 10 6 times respectively in 10 years. The occurrence rate of snails was exponential curve y = 0.1331e0.5844 x, Snail into the early area to increase mainly in the area expanded to a certain extent, then changed to the screw-based growth. Conclusion Increasing the number of snaps is the basis for the proliferation of snails and the effective way to control the spread of snails is to reduce the number of snaps