The Relationship Between Fish Habitat And Fish Diversity In Buyuan River

Lancang-Mekong River is an important international river which has diverse climate type, geography environment and river system, and it is also one of the key abundant biodiversity regions. Because of its rich fish resource, Lancang-Mekong River has been considered as the gene pool of freshwater fish. In recent years, the large-scale hydropower development in Lancing River main stream causes damage to fish habitats and then threatens the safety of fish diversity. One significant impact of cascade hydropower stations on fish ecosystem is that the dam will block off fish passage, the reservoir will submerge fish habitats and the change of hydro-ecological processes will lead to a change in fish habitats. Therefore, study on fish habitat plays an important role on mitigating the ecological influence of hydropower station and maintenance of native fish species diversity.Buyuan River is the first-order tributary of Lancang River whose natural watercourse is comparatively unbroken, and is also the crucial habitat for native fish and migratory fish of Lancing-Mekong River. Based on Buyuan River, this study selected 11 indicators combining the fish data, through the statistic analysis methods, to reveal the fish-spawning preferences for habitat, and the relationship between fish habitat and fish diversity at a multi-scale. Detailed conclusions have been drawn as following:(1) By analyzing and comparing the habitat of fish-spawning river reach and that of non-spawning river reach, considered that fish tend to lay eggs in meandering river channel with wide river width, more central bars and point bars which is larger in the sum of their area (S江+边) and the ratio of their area to river area(S江+边/S河). Further analyzing and comparing the geomorphic feature of spawning site and that of non spawning site, found that the area and perimeter of point bar near spawning site are prominently greater than that of non spawning site at significance level a= 0.05, and this show that fish prefer to spawn near the big point bar.(2) Through analyzing the relationship between the fish habitat characteristics and fish species diversity, conclusions have been drawn as following:the habitat with more native species and endemic species, like Cz, is usually in a winding river channel whose sinuosity is larger than 1.30, and the channel also has relatively more and greater central bars and point bars as well as rapid and slow flow. This kind habitat of Cz can provide suitable habitat for native species of different life habits. The habitat without exotic species, like Ms, is usually has large discharge, rapid flow in dangerous shoal. This kind habitat of Ms is suitable for the native fish which like living in the rapids and not suitable for the exotic fish which like living in slow flow. So this kind habitat can restrict the invasion of exotic species, benefit the native fish diversity and reduce the risk of their competition with exotic species.(3) By comparing the change trend of fish species, native fish species and that of the fish habitat indicators, found that the sinuosity, S 江+边,S江+边/S河 and river width are the critical factors affecting fish diversity. And then considered that the river with lager sinuosity, bigger S江+边/S河 and S江+边/S河, wider river width and rapids flow in dangerous shoal is beneficial to the diversity of native fish.This paper has analyzed the relationship between fish habitat and fish spaw ning, as well as the relationship between fish habitat and fish species diversity i n Buyuan River, and found out fish-spawning preferences for habitat and the hab itat feature beneficial to fish diversity. The results above will provide a case an dscientific basis for the protection of fish diversity as well as the preservation a nd restoration of fish habitat.