通江湖泊

Ecological Impacts on Fish Diversity after Linking

Lakes Disconnected from Central Yangtze River

Abstract

Most of lakes by Central Yantze River used to link with Yangtze. However, these lakes had lost their linkages since 1950s except Dongting Lake and Poyang Lake. This great change resulted in both serious degrading of wetland ecosystem and great lose of biodiversity. Hence, WWF bring forward the idea of “relinking lakes to Yangtze, restoring lifeweb in Yangtze”and launch its practice in 2002. To work in WWF practice, we took baseling survey for fish diversity at five dislinking lakes: Huanggai Lake, Xiliang Lake, Futou Lake, Zhangdu Lake and Chihu Lake, and a linking lake, West Dongting during July, 2002 to April, 2003, respectively. During our survey, we combined historical data and field data to study the differences on dynamics at different period, 1950s, 1980s and present at different lakes. We also focus the study of the difference between linking lake and diskling lakes to to evaluate the significance of linking lakes on conservation for wetland and biodiveristy. Our results are:

1）Linkage between lakes and Yangtze has deep impacts on fish species diversity. Our objective region holds about 125 fish species, which life cycle depend on lakes. These species belong to 12 orders, 23 families, and 74 genera. But, no lakes hold its endemic species. At the other hand, since 1950s，fish diversity at each lake had been decreasing and more than 40% fish vanished from each lake because of the lose of linkage except West Dongting.

2）Cherish and rare species, such as Macrura reevesii et al. had been vanishing

from our objective dislinking lakes since 1980s. Some fishes migrating between river and lake decreased so vastly that they were only found in these years when great floods or lake-river fry introduce (Guan Jiang Na Miao) occurred, such as 1998 flood. In the other hand, endangered species and level increased, and wild fishery production decreased vastly.

3）Lake-breeding modes were stressed and expanded in Central Yangtze River. Wild fishes become the victim of the modes. At the other hand, natural fishery outputs had been decreasing since 1950s and less 1/2 than that in 1950s.

4）Linking lakes differed great from dislinking lakes in lake management, species lose, species composition and annual dynamics even though natural fishery outputs of linking lakes deceased too. It meant that linking lake could alleviate the trend of species lose and maintain original species composition for Yangtze River.

Keywords: Yangtze River, Linking lake, Dislinking lake, Fish diversity,

Fishery resource, Baseline survey