Abstract:

In this study we constructed two Ecopath models representing the Lake Qiandaohu ecosystem of the year of 1999 and 2000,respectively,for the quantitative comparison and analysis of the effects of Aquatic Environmental Protection Oriented(AEPO)Fishery which was begun to be carried out in 2000,on the characteristics of the lake ecosystem.AEPO fishery was considered to be a type of ecological fishery mode that was designed based on the principles of nonclassical biomanipulation and the consumerdriven nutrient recycling theory of ecological stoichiometry.The main technology of it was the stocking of silver and bighead carps and the control of predatory fish,which could not only promote the survival of the stocking fish,but also increase the benthic detritivorous fish.The results showed the implementation of AEPO fishery reduced the ETL of top predators,such as the ETLs of 〖WTBX〗Elopichthys〖WTBZ〗 and 〖WTBX〗Erythroculter〖WTBZ〗 decreased from 385 and 356 in 1999 to 361 and 339 in 2000,respectively.The trophic levels of catch in the lake had also changed,i.e.,the catch had changed from Trophic Level III (500%) in 1999 to Trophic Level II (4874%) in 2000,which further led to the drop of average ETL of the whole fishery from 274 in 1999 to 261 in 2000.Both ecosystem productivity and ecosystem size of Lake Qiandaohu in 2000 were lower than those in 1999,i.e.,the ecosystem productivity of the lake decreased from 98780 t/（km2·a）in 1999 to 66250 t/（km2·a） in 2000 with 3323% decline, while sum of all consumption, sum of all exports and sum of all respiratory flows were decreased by 2965%, 3569% and 3060%, respectively. Moreover, total system throughput reduced from 35285 t/（km2·a） in 1999 to 24271 t/（km2·a） in 2000.Indices which indicate the maturity of an ecosystem(e.g. decline of Pp/R and Pp/B,increase of FCI and Finn’s average path length) all showed that the aquatic ecosystem of Lake Qiandaohu was more developed in 2000 than in 1999.