Study On Predatory Effect And Control Technology Of Ischnura Heterosticta Larva On Misgurnus Anguillicaudatus Larva

After extensive research, it was discovered that I. heterosticta larva is important predator, which can be decimated M. anguillicaudatus larva. However, the predation of predators on M. anguillicaudatus has never been reported. In view of this, this paper studied I. heterosticta larva on M. anguillicaudatus larva predation effect, through the predation effect models were set up to provide the theoretical foundation for prevention and control of I. heterosticta larva. On this basis, further carried out the experiments of killing I. heterosticta larva by lambda-cyhalothrin, trichlorfon and homemade booby-trap to provide the technical foundation. The results are as follows:1. Predatory effect of I. heterosticta larva to M. anguillicaudatuslarvaStudied the predation of I. heterosticta larva to M. anguillicaudatus larva based on the predator-prey relationship theory. Results of experiments showed that:(1) The predation functional response of I. heterosticta larva to M. anguillicaudatus larva belonged to type Holling-II. With the increase of M. anguillicaudatus age, the moment attack(a?) and the largest preying amount per day(1/Th) were reduced. The preying amount was increased as prey density increases.(2)The predatory function of different specifications of I. heterosticta larva to M. anguillicaudatus larva had significant difference. For I. heterosticta larvae with different body lengths(16.3±0.2mm, 13.1±0.3mm, 9.8±0.2mm and 5.8±0.3mm) to 3-day-age larvae of M. anguillicaudatus, the moment attack and the largest preying amount per day were 0.8349, 0.5724, 0.2002 and 0.0432,as well as 27.39, 18.99, 9.49 and 3.14, respectively.(3) With the I. heterosticta larvae density increases, the mutual interference between the individuals resulting in a single I. heterosticta larvae reduced the time looking for prey.Under intraspecific competition, predatory effect rate(E) as a function of density(P) was E(28)0.1403 ?P-0.2361.(4) With the increase of M. anguillicaudatus larvae and I. heterosticta larvae density, interference effect increases obviously, predatory efficiency rate(E) drop, but had little impact on preying amount, the model of interspecific interference was Na=(?).2.Results of killing I. heterosticta larva by lamba-cyhalothrin and trichlorfonThe acute toxicity of lambda-cyhalothrin and trichlorfon to I. heterosticta larva was tested under the hydrostatic conditions and establish corresponding mortality- drug concentration logarithm linear regression equation.The results showed that the sensitivity of I. heterosticta larva to lambda-cyhalothrin is greater than to trichlorphon.The LC50(24,48 and 96 h) of lambda-cyhalothrin were 6.44 ug/L, 5.31 ug/L and 4.57 ug/L,respectively,and the safety concentration was 0.89 ug/L.The LC50(24,48 and 96 h) of trichlorphon were 0.81 mg/L, 0.65 mg/L and 0.56 mg/L,respectively,and the safety concentration was 0.11 mg/L.Further carried out the acute toxicity of the two aquacultural drugsto the 5-day-age and 25-day-age of M. anguilicaudatuslarvae. The results showed that the mortality rate of lambda-cyhalothrin on I. heterosticta larva was less than or equal to 5.8%, not as the drug for prevention and control of I. heterosticta larva in the M. anguilicaudatus larvae rearing pond. But, it was obvious killing effect that the mortality rate of trichlorfon on I. heterosticta larva can reach 89.6% above. Thus, trichlorfon could be conventional drug for killing I. heterosticta larva.3. Effect of homemade booby-trap on I. heterosticta larvaThe study found that I. heterosticta larva has phototaxis habit and can lead to suffocation by oil film. In view of this, the booby-trap was designed and killing test of booby-trap on I. heterosticta larva was carried out. The results showed that the booby-trap was simple, efficient, economical and practical, safe. Set the device in the water depth and water plants all had effects on killing I. heterosticta larva. It can improve the killing performance that the device was arranged at the depth of 30-40 cm and was implanted water plants into. The device had obvious killing effect on I. heterostictalarva, mortality rate was about 20%-30%(12h), and no lethal effect on M. anguilicaudatus larva.Therefore, the device can be used as the main technical means of killing I. heterosticta larva to promote in the M. anguilicaudatus larvae rearing pond.