青虾围塘养殖,是上虞市调整农业产业结构过程中出现的新的养殖方式,每年可为农民增加收入近千万元。然而,经多年养殖后,虾塘老化,虾病增多,产量不断下降。至2003年,养殖亩效益已由四年前的1550元降至865元,下降44%。原来是一年养殖两期青虾,但由于第二期青虾发病更严重,产量更 Freshwater prawn pond cultivation, Shangyu City, adjust the structure of agricultural industry in the emergence of new breeding methods, each year for farmers to increase revenue nearly 10 million yuan. However, after years of aquaculture, shrimp ponds are aging and shrimp diseases are increased, and their yields are declining. By 2003, the benefit of aquaculture farming had dropped to 865 yuan from 1,550 yuan four years ago, a decrease of 44%. The original year of breeding two shrimp, but due to the second phase of the incidence of more serious shrimp, more yield