南水北调输水模式中相关因素对钉螺北移扩散的影响

Impact of factors related to pattern of water diversion of South-to-North Water Diversion Project on spread north of Oncomelania snails

目的观察南水北调工程输水模式中相关因素在钉螺扩散中的作用,以评估南水北调东线工程对钉螺北移扩散的影响。方法将一定数量标记钉螺吸附于载体并漂浮于水面上,用水泵现场抽提,统计过泵钉螺数。将一定数量标记钉螺投放于不同深度水塘(沟)水下,经一定时间后沿水塘(沟)水线及在水面漂浮的稻草把上查找钉螺,观察钉螺迁移扩散情况。钉螺幼螺雌雄配对后,采用螺笼法在现场按不同密度进行放养,观察1个生殖年后笼内钉螺密度。结果附着于漂浮物上的钉螺在距进水管口100、50cm和20cm处,随水被吸通过进水管径为80cm的水泵通过率分别为2.45%、3.93%和43.46%;钉螺在距进水管口20cm和10cm处,随水被吸通过进水管径为20cm水泵的通过率分别为72.07%和91.00%。在5个现场水塘或沟,共投放36600只标记活钉螺,在投螺15～120d后,沿水塘(沟)水线及在水上漂浮的稻草把上均未检获标记钉螺。当幼螺密度≤2对/0.16m2时,难以增殖。结论在南水北调东线工程建设中,只要采取必要控螺措施完全有可能降低或消除钉螺向北扩散的危险。

Objective To investigate the role of relevant factors concerning the pattern of water diversion of the South-to-North Water Diversion Project in the spread of Oncomelania snails,so as to evaluate the impact of the Eastern Route Project of the South-to-North Water Diversion Project on the spread north of snails. Methods Some marked snails were attached to the carrier and floated on the water surface. The water pump was used for pumping,and the number of the snails passing through the pump was counted. Some marked snails were thrown into the ponds or ditches,after a certain time,the snails were collected along the ponds （ditches） and in the straw handles that floated on the water surface,and the diffusion of the snails was observed. The juvenile snails,with a male∶female ratio of about 1,were put into snail cages in the field with different densities,and the snails in the cages were collected and observed after 1 year. Results When the diameter of the infall pipe of the water pump was 80cm,and the distances between the throwing site and infall pipe were 100,50 cm and 20 cm,the passing rates of the snails attached to the floaters were 2.45%,3.93% and 43.46%,respectively. When the diameter of the infall pipe of the water pump was 20 cm,and the distances between the throwing site and infall pipe were 20 cm and 10 cm,the passing rates of the snails attached to the floaters were 72.07% and 91.00%,respectively. A total of 36 600 marked living snails were put into 5 ponds or ditches,after 15-120 d,there were no marked snails found along the ponds （ditches） or in the straw handles floating on the water surface. The juvenile snails could hardly reproduce when its density was less than 2 pairs/0.16 m^2. Conclusions During the construction of the Eastern Route Project of the South-to-North Water Diversion Project,it will decrease or eliminate the risk of spread north of the snails as long as reliable interventions for snail control are implemented.