Construction and management of fish passage on Shaliu River adjacent to Qinghai Lake based on ecological restoration

Abstract: Gymnocypris przewalskii belongs to subfamily of Schizothoracinae, family of Cyprinidae and order of Cypriniformes, and it is an endemic species only distributed in the Qinghai Lake and its adjacent rivers and lakes. It possesses migration characteristics, and goes upstream from the lake to surrounding rivers in the reproduction season. However, several dams built on the rivers flowing into the lake with the agricultural development in the Qinghai Lake region since 1970s, severely blocked its migration passages, leading to obviously decreasing of resources of Gymnocypris przewalskii in recent years. To protect Gymnocypris przewalskii, three kinds of fish passages on the dams of rivers flowing into the Qinghai Lake were introduced, which were types of guide wall, simple steel modular and ladder slope, respectively. 1) The guide wall type fish passage was separately constructed on the dams in the Shaliu River, Quanji River and Haergai River in 2006, which were built along river side, but it had several defects because of the lack of experience. 2) The simple steel modular type fish passage was designed and constructed on the dam of the Shaliu River in 2008, Based on biological characteristics of Gymnocypris przewalskii and the basic situation of the dam and environmental conditions of the Shaliu River. After considering inlet location of fish passage, suction flow and hydraulic conditions within passage, the inlet was located at the area with aggregated fish and slow current velocity. The water flow was 0.5 m/s, the current velocity was 0.1-0.25 m3/s, as well as the slope of 1:10 within fish passage. 3) The ladder slope type fish passage was built on the dam of Shaliu River in 2010, which used two types open fishponds of multi-ladder and slight slope. Fish passage without hindrance had been almost come to be real through this type. This type was designed according to basic theories and related parameters of simple fish passage. The length was 80 m and the width was 1.3 m for each platform, and the outer edge width was 0.3 m, height difference of outer edge between two adjacent levels was 0.15 m, as well as the height difference between outer edge and adjacent lower inner edge was nearly 0.35 m. Fish passage had 18 levels in total, and its plane width was 23.4 m, vertical height was 3 m and length extended to 160 m. In addition, the suggestions on design of fish passage in China had been discussed. Four highlights were provided, including: 1) The fish gathering area should be considered when locating the inlet; 2) Migration ability of fish should be thought over while designing; 3) The passage should be improved and maintained regularly in the process of operation; 4) The design of fish passage needs the attention and joint effort of experts from multi-principles. Furthermore, the strategies on construction and management of fish passage based on ecological restoration had been presented, which included: setting the goal of fish passage design based on the ecosystem function value, realizing the idea of fish passage design serving for fish, establishing the systematic ways for fish passage design, construction and maintenance.