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目的 掌握洪灾后钉螺消长规律 ,进一步评价洪涝灾害对长江下游钉螺消长和扩散的影响。方法 每年采用系统抽样结合环境抽查的方法进行江滩钉螺调查 ;采用打捞法定点观察漂浮物携螺扩散情况。结果 1998～ 2 0 0 3年钉螺面积平均每年递增 11.80 % ,而 1998～ 2 0 0 3年阳性钉螺面积则平均每年递增 2 9.2 5 %。阳性螺面积随钉螺面积的增加而增加。江苏段洲滩有螺框出现率、阳性螺框出现率、钉螺感染率和阳性螺密度在洪灾后 2年内均呈不同程度下降 ,而从第 3年开始出现快速上升趋势。 2 0 0 2年打捞漂浮物检获钉螺 6 83只 ,2 0 0 3年检获 384 6只。调查表明钉螺吸附于漂浮物扩散高峰为 8月。结论 洪涝灾害短期内可促使钉螺蔓延扩散 ,表现为钉螺面积大幅度增加 ,后期则以钉螺密度增长为特征 ;长江水系钉螺在汛期可吸附于漂浮物扩散。
Objective To understand the rule of the growth and decline of Oncomelania snails after flooding and further evaluate the influence of flood disasters on the growth and spread of Oncomelania snails in the lower reaches of the Yangtze River. Methods A systematic sampling and environmental sampling method was used to investigate snails on the beach every year. Results The snail area increased by 11.80% annually from 1998 to 2003, while the positive snail area from 1998 to 2003 increased by an average of 2 9.25% annually. Positive snail area increases with the increase of snail area. The occurrence rate of screw frame, positive screw frame, snail infection rate and positive spiral density of Duanzhou Beach in Jiangsu Province all decreased to different extents within 2 years after flooding, but began to increase rapidly from the third year. In 2002, 6 83 snails were seized from floating debris and 384 from 2003. Surveys show snail adsorption to the float diffusion peak in August. Conclusion The flood disaster can promote the spread and spread of snails in a short period of time, which is characterized by a significant increase of snail area and later growth of snail density. Snail of the Yangtze River can be adsorbed to the floating matter during flood season.