Habitat Suitability Evaluation Of The Acipenser Dabryanus In Chongqing Section Of The Yangtze River

The upper Yangtze River is one of the areas with the most abundant freshwater fish resources in China.In recent years,due to the development of water conservancy and hydropower projects,sand excavation and quarrying of the Yangtze River and water pollution,the river shape and hydrological process in this section have changed to a certain extent,which will affect the growth and reproduction of fish and fish resources to a certain extent.In the history of the Acipenser dabryanus,the spawning ground is mainly distributed in the section from Yibin to Hejiang in the upper Yangtze River.The young fish go down the river to the three Gorges River for bait,as far as Shashi and above the river,and then return to the Sichuan section to breed after sexual maturity.So the growth and reproduction of the Yangtze River Sturgeon needs a long natural channel.Based on this,this study selected 8 sampling sites in Chongqing section of the upper Yangtze River from July 2020 to September 2021,including Yangshi,Sanpaohe,Wanjiatuo,Songji,Zhuyang,Juzinao,Waduanshan and Dingjiatuo.Aquatic organisms and water quality factors were used to evaluate the water health,and the habitat suitability index model was used to evaluate the potential habitat suitability of the Acipenser dabryanus.In view of the main habitat factors restricting the growth and reproduction of Acipenser dabryanus,some suggestions on habitat restoration were put forward in order to provide theoretical data support for the restoration of natural reproduction of Acipenser dabryanus in the field.The main results of this study are as follows:1.Health evaluation of waterThe results of water health evaluation show that the annual average water temperature,transparency,conductivity,pH,dissolved oxygen concentration,total phosphorus concentration and total nitrogen concentration in Chongqing section of the upper Yangtze River are 19.20℃,92.90 cm,446.20 ms/cm,8.49,8.69 mg/L,0.14 mg/L and 1.36 mg/L respectively.The annual average concentration of ammonia nitrogen is 0.53 mg/L and the annual average value of permanganate index is 4.54 mg/L.According to the comprehensive pollution index method,dissolved oxygen,total nitrogen,total phosphorus,ammonia nitrogen and permanganate index are selected as pollution factors.It is concluded that the annual water pollution level is "moderate pollution",and the difference among sampling sites is not significant.The time dimension shows that the water quality is poor in autumn.Three kinds of plankton diversity index were used to evaluate the health of water body,the results of Margalef diversity index were unreliable,and the annual average results of Shannon-Wiener diversity index and Pielou evenness index showed "light pollution".2.Evaluation of habitat suitability index modelThe evaluation results of habitat suitability index model showed that the key habitat factors of Acipenser dabryanus during breeding period were water temperature,water depth,flow velocity and sediment type,while those in non-breeding period were water depth,sediment type and zoobenthos density.The weights of key habitat factors were calculated by AHP analytic hierarchy process,and the annual average HSI of sampled waters was calculated by weighted average method,which was "suitable".For potential spawning grounds,Zhuyang had the highest average HSI,Yangshi is the lowest,April HSI is the highest,November is the lowest,Dingjiatuo is the highest,Sanpaohe is the lowest,the HSI the highest in May and the lowest in February.3.Habitat restoration recommendationsHabitat restoration suggestion according to the results of this study,it is suggested that the artificial substrate should be put into the large Wantuo section of the upper Yangtze River to increase the density of benthos,and that the cascade hydropower stations of the Jinsha River should increase the discharge and discharge of the Yangtze River Sturgeon during the breeding season.it is suggested that the Chongqing section of the upper Yangtze River should reduce the discharge of domestic and industrial sewage,reduce the nitrogen content in the river water and improve the water quality.