Evaluation Of The Fish Community Structure And Habitat Suitability In Huntai River

Ecosystem health refers to the fact that the ecosystem has resistance and resilience to long-term natural disturbance.It can maintain its own organizational structure and maintain stability,and has the ability to operate on its own.Indenx of biotic integrity（IBI）is the most widely used indicator in the current research and evaluation of aquatic ecosystem health.Fish are the apex predators of river ecosystems and the main indicators for water ecosystem monitoring.The decline of biodiversity and degradation of community structure are both closely related to a decline in habitat quality.Studies focused on the relationship between the fish community and environmental factors of the habitat mostly evaluate the environmental factors affecting the spatial and temporal distribution of fish communities through multivariate statistical analysis.Such qualitative analysis can only summarize the driving environmental factors,but cannot accurately quantify the response relationship between the fish community and environmental factors.In the Huntai River,Liaoning province,for example,a study based on a water ecological investigation of the whole basin was conducted using data from 162 stations to evaluate the level of community species diversity,the Shannon diversity index,and functional groups（divided into five feeding functional groups:benthic animal feeding,insects feeding,fish feeding,omnivorous fish feeding,and plant feeding）under three kinds of community organization characteristics,environmental factors of river habitats,and quantitative response of the relationships within the fish community.The model was constructed using F-IBI integrity index model,correspondence analysis（CCA）,the weighted average return（WA）,and critical indicator species analysis（TITAN）methods.The optimum and threshold values for the environmental factors of the habitat under different fish community structure characteristics were calculated.The results are as follows:1、After screening,five candidate indicators were finally determined as parameter indicators of F-IBI indicator system,which were M3（the percentage of arroidea subfamily）,M11（the percentage of carnivorous fish）,M12（the percentage of phytophagous fish）,M14（the percentage of sensitive fish）and M19（the percentage of cold-water fish）.mong them,34 sites were in the healthy level,accounting for 21%of all sites;49 sites were in the good level,accounting for 30.2%of all sites;45 sites were in the general condition,accounting for 27.8%of all sites;34 sites were in the poor condition,accounting for 21%.2、The results showed that the velocity,BOD₅,NH₄⁺-N,Cond,and IOS were the environmental factors that significantly influenced the spatial distribution of the fish community structure in the Huntai River basin.According to the WA analysis,fouling resistance fish have optimum values of NH₄⁺-N and BOD₅,have a high conductivity,and environmental factors（velocity,BOD₅,NH₄⁺-N,Cond,and IOS）that favor the functional group of the omnivorous fish and the high diversity of fish community(Shannon diversity index（2-3]interval）have higher optimum values,the extremely high levels of fish community diversity(Shannon diversity index（3-4]interval）and fish predators for the habitat environmental factors,velocity,BOD₅,Cond,and IOS show the lowest optimum values.3、The TITAN results showed that the fouling resistance for Carassius auratus andPseudorasbora parva of NH₄⁺-N,BOD₅,and Cond indicated a positive response.However,the results for Phoxinus lagowskii,Lampetra morii,and other species sensitive to NH₄⁺-N,BOD₅,and Cond indicated a negative response.The fish community diversity level of the velocity and IOS presented a positive response,with a change in the threshold value range of:0.46-0.7 m/s and 1.25-1.74,respectively.For NH₄⁺-N,BOD₅,and Cond it showed a negative response,with threshold ranges of 0.11-0.39 mg/L,1.04-1.98 mg/L,and 189.78-330.00μs/cm,respectively.The functional groups of the fish community exhibited a negative response to the changes in NH₄⁺-N and Cond as a whole,and the threshold ranges were 0.21-0.89 mg/L and 202.90-456.03μs/cm,respectively.The results showed that the optimum value and positive response threshold of NH₄⁺-N and Cond were higher in pollution resistant species,such as Carassius auratus,Abbottina rivularis,and Phoxinus lagowskii,whilst Lampetra morii adapted to a higher velocity and IOS.Concerning the level of fish community diversity,the optimum value and threshold for the environmental factors of the habitat first increased and then decreased,in accordance with the increase in the Shannon diversity index.In the middle and lower reaches of the Huntai River,fish of the omnivorous functional group had higher optimum values and positive response thresholds for BOD₅,NH₄⁺-N,and Cond.Through judging the health status of Huntai river basin through F-IBI,and the quantitative analysis of the community and environmental factors,the relationships between the important species of fish（such as Lampetra reissneri）can provide a relatively accurate assessment of the community,species diversity,and key functions of the environmental characteristics of the habitat.This will assist in achieving the protection of resources for important fish species and key habitat restorations.The research is necessary to develop the ecological restoration of the river basin,advise management decisions on the control of the total amounts of pollutant discharge in river basin ecosystem,and provide basic data and a scientific basis for environmental protection.