稻田养草鱼灭蚊幼虫的实验研究

在稻田中放养1.9尾细/m~2草鱼,78d后中华按蚊幼虫密度下降87.4％,三带喙库蚊幼虫密度下降80.0％,残存的幼虫有73.3％为新孵化的1—2龄幼虫。抽样解剖10条鱼的30％和89份鱼粪中有24.7％检出蚊幼的呼吸管(孔)。在盛清水的容器中,每条鱼24h平均捕食蚊幼861.5只,容器中加入草和藻类等食料后,捕食蚊约为661只,在模拟稻田中鱼仅捕食蚊幼362只。试验的结果证实草鱼能捕食大量蚊幼,降低稻田中蚊幼密度,同时也增加了稻谷和鱼的产量。

BREEDING GRASS CARP AGAINST MOSQUITOES IN RICE FIELD

In this experimental study, grass carp were bred in rice field (1.9 fish/m2) to control mosquito larvae. 78 days after treatment, the larvae population of An. sinensis and Cu. tritaeniorhynchus dropped down by 87.4% and 80% respectively. Newly hatched 1-2 instar larvae accounted for 73.3% of the larvae remained in rice field after treatment. Eighty-nine samples of fish feces taken from rice field and 10 fishes were examined for breathing sy-phons of mosquito larvae. Breathing syphons were found in 22 fecal samples (24.7% posi-live) and 3 fishes (30% positive). The average number of mosquito larvae devoured by one fish was 861.5 in 24 hours in tap water and 661 in 24 hours in water containing grass and aquatic plants. The simulated field test showed that the average number of mos-quito larvae devoured by fish was 362 larvae in 24 hours. The field trial indicated that the grass carp could not only cut down the mosquito larvae population but also benefit the peasants by increasing the production of both fish and rice.