River Habitat And Its Relationship With Fish Community In The Upstream Of Lijiang River

River habitats was classified and assessed in the upstream of the Lijiang River,and the composition and distribution of fish communities among various habitat types was investigated,and the relationship between river habitats and fish communities and between habitat quality and biological conditions was explored,which is in order to provide a scientific theoretical basis for watershed ecological protection and river health management.The main results of this study are as follows:(1)Combined with the classification of river habitats at home and abroad,according to the characteristics of mountain streams in our country and the morphology characteristic of the study area,the habitat in the upstream of Lijiang River was classified into three groups:hydrostatic habitat,slow flow-habitat and fast-flow habitat.Refinement of each group,they were classified into seven categories.Among them,the hydrostatic habitat included pool and plunge,the slow-flow habitat included glide,run and secondary channel pool,while fast-flow habitat included riffle and cascade,respectively.There were significant differences in environmental variables among different habitat types.(2)A total of 2,968 fish individuals were collected during this study,which belonged to 4 orders,11 families,28 genera and 37 species(Appendix 1).Among these;like other water bodies in China,the Cypriniformes was the most species-rich order,which accounting for 62.16%of the total species.The dominant species were Pseudogastromyzon fangi(25.64%),Zacco platypus(21.16%)and Acrossocheilus parallens(12.84%).The species diversity of fish community varied in different habitats in the upper reaches of the Lijiang River.The highest Margalef richness index(Dma)was found in secondary channel pool habitat(4.12),whereas the lowest Margalef index appeared in plunge habitat(2.32).Shannon-Wiener diversity index(He')of glide habitat(2.50)was higher than the rest habitats.The maximum of Simpson dominance index(?)appeared in pool habitat(0.35),while minimum at glide(0.10).On the contrary,the highest Pielou evenness index(Je)was in glide habitat(0.82),while the pool habitat was the lowest(0.54).Non-metric Multidimensional Scaling(NMDS)ordination was applied to analyze the distribution of fish communities in different habitat types and the result illustrated variation in fish assemblage composition based on habitat types.(3)Canonical Correspondence Analysis(CCA)ordination revealed that velocity,water depth,substrate size,pH,conductivity and turbidity had remarkable relationships with fish assemblages,while water temperature and dissolved oxygen were less important.(4)Habitat assessment of "Rapid Bioassessment Protocols"(RBPs)was used as the method to assess the habitat quality in the upstream of Lijiang River.The result showed that 26 sites scores of habitat index ranged from 82 to 155.Among them,3 reaches achieved "Optimal"(HI score>150),12 reaches were "Suboptimal"(HI score=120?150),9 were "Marginal"(HI score=90?120)and 2 were "Poor"(HI score=60?90).Three indicators in most reaches in the study area were rated "Optimal",they were Velocity/depth regimes,Frequency of riffles(or bends),Bank vegetative protection,while two indicators of Channel flow status and Bank stability in most reaches were "Marginal" level.Channel alteration was the lowest scores indicator in the study area,and most of the reaches was rated "Poor".(5)Based on the F-IBI indicator system in the upper reaches of the Lijiang River,river health condition of 26 sampling sites in this study was evaluated.The results showed that 12 sites achieved "Healthy"(IBI score>40),8 sites were "Fair"(IBI score=27?40)and 6 were "Poor"(IBI score= 13?27).The correlation analysis showed that the IBI score was significantly positively correlated with the HI score.The higher HI scores of the reach,the higher IBI value in general.The correlation analysis between habitat indicators and biological parameters showed that,all habitat indicators but Bank vegetative protection had significant or extremely significant correlation with biological parameters,which further demonstrated that the quality of river habitat could affect the biological state of aquatic organisms.