保水渔业对千岛湖食物网结构及其相互作用的影响

为预防千岛湖连续暴发了2a(1998—1999)的蓝藻水华和改善千岛湖水质,于2000年起在千岛湖开展了以人工放养鲢鳙和控制凶猛鱼类为主要措施的保水渔业试验。作为试验的主要研究内容之一,通过构建1999和2000年千岛湖生态系统的Ecopath模型,比较分析了实施保水渔业对千岛湖生态系统食物网结构及其相互作用的影响。结果表明:实施保水渔业,使千岛湖中的银鱼和鲤生物量减少,而鲌类(主要是蒙古鲌)、鲴类和大眼华鳊等增加;使各种鱼类的捕食者和食饵生态位重叠指数下降;各主要鱼类的相互作用中,鲢、鳙对鳡、鲌的促进作用增强,鳡对鲌的抑制作用及鲌对虾类、银鱼和鲤等以及银鱼对浮游动物的抑制作用减弱,鳙对银鱼、大眼华鳊对鲤的抑制作用增强。这些影响,使千岛湖食物网结构更趋合理,如底层碎屑食性鱼类如鲴类等的增加,有利于营养物的再循环和再利用,从而增强了水体对营养物的净化作用。

Impacts of aquatic environment protection oriented fishery on the structure of food web in Lake Qiandaohu

A study was conducted in 2000 to evaluate impacts of an aquatic environment protection oriented (AEPO) fishery on the structure of food web in Lake Qiandaohu. The AEPO fishery was based on the stocking of silver and bighead carps and the removal of predatory fish and was designed to improve our understanding of ecosystem dynamics to prevent the recurrence of cyanobacterial bloom occurring in 1998 and 1999 and to improve water quality in the Lake Qiandaohu. We constructed Ecopath models of the lake ecosystem for 1999 and 2000, respectively, to compare and analyze quantitatively the changes of the food web structure before and after the implementation of AEPO fishery in the lake. The results showed that AEPO fishery resulted in a reduction of ice fish and common carp biomass and an increase of Culters (esp., Culter mongolicus), Xenocypris and Sinibrama biomass, etc., reducing the niche overlap of both preys and predators in the ecosystem. In addition, The AEPO fishery enhanced the bottom-up effects of bighead carp and silver carp on predatory fish such as Elopichthys and Culters, reduced the suppressing effects of Elopichthys on Culters, of Culters on shrimp, ice fish and common carp, and of ice fish on zooplankton, and enhanced the inhibitory impacts of bighead carp on ice fish, Sinibrama and common carp. These effects of AEPO fishery, making the food web structure optimal such as increasing detritivorous fish like Xenocypris, can result in the enhancement of nutrient recycling and reutilization, eventually leading to the enhancement of purification capability of the lake ecosystem.