Fish Resources Status And River Health Assessment In Heishui River,a Tributary Of The Lower Reach Of Jinsha River

The Heishui River is a primary tributary of the lower reaches of Jinsha River,It is an important habitat and a priority tributary for protection of fish in the lower reaches of Jinsha River,and has abundant fish resources.From upstream to downstream,the mainstream of Heishui River has four cascade hydropower stations,Sujiawan,Gongdefang,Songxin and Laomuhe,among which the Laomuhe hydropower station was dismantled in December 2018.The structure of fish communities in Heishui River has been caused serious interference and damage due to human activities such as hydropower station construction,overfishing and sand excavation from river channels.Based on the survey data from November 2018 to September 2019,the status of fish resources and river health in Heishui River were evaluated,aiming to provide a scientific basis for the protection of fish resources and ecological restoration in Heishui River.The main research results of the paper were as follows:1.A total of 44 fish species were collected in Heishui River from November 2018 to September 2019,belonging to 4 orders,10 families and 33 genera,of which 15 species belong to 14 genera of Cyprinidae,accounting for 34.09% of the total fish species;12 species belong to 7 genera of Cobitidae,accounting for 27.27%;3 species belong to 3 genera of Homalopteridae,accounting for 6.82%;7 species belong to 3genera of Bagridae,accounting for 15.91%;2 species belong to 1 genus of Gobiidae,accounting for 4.55%.There was only 1 species in each of Siluridae,Sisoridae,Amblycipitidae,Synbranchidae and Cichlidae,each accounting for 2.27%.Among the44 species of fish,11 species were endemic species of the upper Yangtze River,including Percocypris pingi,Schizothorax wangchiachii,S.prenanti,Xenophysogobio nudicorpa,Oreias dabryi,Paracobitis potanini,Triplophysa xichangensis,T.anterodorsalis,Leptobotia elongate,Jinshaia sinensis,and Beaufortia szechuanensis.It is included in the "Red List of China's Vertebrates" with 4 vulnerable species,1endangered species,2 near threatened species,and 4 protected animals in Sichuan Province.One invasive species is the Oreochromis niloticus.2.The dominant fish species in Heishui River included Paracobitis varigatus,Schizothorax wangchiachii,Triplophysa daqiaoensis,Zacco platypus,Paracobitis potanini and Glyptothorax sinense,which accounted for 28.44%,28.01%,16.66%,7.18%,5.09% and 3.36% of the total weight of captures,respectively.The similarity index analysis of fish composition from different river sections showed that the similarity between the upper reaches of Sujiawan Dam and the lower reaches of 765 backwater point in Heishui River was the lowest(24.32%),whereas the upper reaches of the Sujiawan dam and the reaches from Songxin dam site to laomuhe dam site had the highest similarity index(61.90%).The result by using autecology matrix analysis showed that the fish community in Heishui River were mainly composed of riffle,with lower mouth,and omnivore group.The fish diversity index showed an increasing tendency from upstream to downstream of Heishui River and the variation of diversity index in different seasons was not significant(P>0.05).Abundance biomass comparison(ABC)curve showed that the structure of the fish community in Heishui River was moderately disturbed.The results showed that,compared with historical data,the fish in Heishui River exhibited a trend of miniaturization and the protection measures should be strengthened.3.According to the investigation,literature records and specimens collected in the Herbarium of the Yangtze River Fisheries Research Institute,there had been a total of71 fish species in Heishui River,belonging to 4 orders,10 families,and 47 genera.After excluding one introduced species,the fish fauna of Heishui River was analyzed at three levels of order,family and genus according to the traditional and the Value of Faunal Presence(VFP)methods.The results showed that the results of the two methods were quite different,and the family,genus that dominate in the traditional method had a low Value of Faunal Presence.On the contrary,some of the local distributions,and small families and genera,had a high Value of Faunal Presence.Therefore,the analysis result of the Value of Faunal Presence could better explain the characteristics of fish composition in Heishui River.In addition,comparing the fish fauna of Heishui River with the Jinsha River,Niulan River and Dawenxi showing a high degree of similarity.4.Three study sites were selected as reference sites,which were the Heishui River estuary,the upstream of the hydrometric station,and the 825 backwater point.Eight metrics were selected form 27 candidate metrics by distributing range analysis,discriminatory power analysis and Pearson's correlation analysis to develop the final biotic integrity index of fish(F-IBI)evaluation system.The IBI value of each sampling site was then calculated using 1,3,5 assignment method and the ratio method to assess the health state of the Heishui River,and the status of river health was categorized into five levels: “no fish”,“very poor”,“poor”,“fair” and “healthy”.The result showed that although the result of the 1,3,5 assignment method and the ratio method was not exactly the same,the trend was consistent.The health status of most sampling points in Heishui River was at a "poor" and "fair" level.