Preliminary Study On Habitat Quality And Habitat Suitability Of Gymnocypris Przewalskii Of Shaliu River

Gymnocypris przewalskii is the only aquatic economic fish in Qinghai Lake.In the1940 s and 1960 s,G.przewalskii was the main catch of Qinghai Lake.However,due to the poor living conditions,excessive fishing intensity and other factors,the resources of G.przewalskii continued to decline.G.przewalskii was listed as a valuable aquatic animal in China in 1964 and was listed as an endangered species in the Chinese species Red list of the Biodiversity working Group of the China International Cooperation Committee for Environmental Development in 2004.G.przewalskii is mainly distributed in Qinghai Lake and its surrounding rivers.Among them,Shaliu River is an important habitat of G.przewalskii,and it is also one of the reproductive migration channels and spawning grounds for parent fish in the breeding season.It is the habitat in the whole life cycle of G.przewalskii,especially in the embryonic and juvenile stages.It is of great significance to the growth and reproduction of G.przewalskii.In recent decades,due to the frequent occurrence of agricultural irrigation,arid climate,environmental pollution and poaching around the Shaliu River,as well as the obstacles of water-related projects such as bridges over the Shaliu River,the reproductive migration channel of G.przewalskii has been blocked.the channelization of the river is serious,resulting in the degradation and loss of its habitat and the destruction of the spawning ground,in order to carry out targeted protection and restore the resources of G.przewalskii more quickly and effectively.It is necessary to study the migratory river habitat of G.przewalskii.In this paper,after the preliminary evaluation of the habitat quality of G.przewalskii in the waters of Shaliu River,the habitat suitability was evaluated,and finally the habitat suitability curve was constructed.A preliminary understanding of the quality of the existing G.przewalskii habitat and spawning ground in the Shaliu River,to fill the gap in the research on the habitat of G.przewalskii,and to provide scientific reference for related research and habitat protection.The main results are as follows:(1)Taking the reach from Shaliu River Estuary to Wayan Mountain 60 km as the study area,using Analytic hierarchy process,the environmental factors such as flow velocity,depth,water temperature,dissolved oxygen and p H are quantified and weighted,and finally the comprehensive habitat quality index is calculated,and the index is used to evaluate the existing habitat quality from July to August 2020.The results show that the comprehensive habitat quality evaluation index above "general" accounts for 96.67% of the total,indicating that the Saliu River can provide a better habitat and spawning environment for G.przewalskii.However,in recent years,some major projects dominated by bridge construction and human activities have led to the interruption of flow in some sections of the river,which has a significant impact on the habitat environment of the Shaliu River.The spawning behavior of parent fish is mostly completed in the place where the bottom of the river bed is pebble and less sand and gravel,the size,shape and color of the pebbles are different,and there is no or little attachment of sediment and moss on the surface,and the flow speed is slow and the depth is shallow where the fish eggs exist.The richness of eggs in the spawning ground of G.przewalskii was negatively correlated with the amount of water in the river.every time the flood peak appeared,the richness of eggs was maintained at a low level.(2)During the reproductive migration of G.przewalskii in July 2020,the distribution and hydrological pattern of spawning ground of G.przewalskii in Shaliu River Basin were investigated.The environmental factors which have certain influence on the migration and spawning behavior of parent fish are selected as habitat indicator factors,and the frequency distribution method is used to simulate the suitability of the selected environmental factors one by one,and their suitability curves are drawn.Then,according to the curve,the range value of each environmental factor suitable for reproduction and spawning of G.przewalskii is obtained.Then use the analytic hierarchy process to calculate the weight of the selected factors,and finally use the weighted average method to calculate the G.przewalskii habitat suitability index of each survey site in the Shaliu River basin.The results showed that the G.przewalskii mainly propagated and spawned in the water with flow velocity 0.1～0.4 m/s,water depth 0.06～0.15 m,temperature 13～18 ℃ and turbidity 1.52～10 NTU,and the average suitable degree was more than 0.6.The distribution of habitat suitability index(Habitat Suitability Index,HSI)showed that the habitat indexes of D34,D31,D27 and D24 were higher in Waters 2 and 3,all above 0.85,and D43 was the highest(0.9261).