Assessment of the Huntai River in China using a multimetric index based on fish and macroinvertebrate assemblages

Recently, the concurrent use of multiple taxonomic groups in stream bioassessment is becoming increasingly common because the responses of each group to anthropogenic stressors may be different. In this study, a multimetric index based on fish and macroinvertebrate assemblages for the Huntai River basin (MMIHT) was developed using a dataset covering 54 sampling sites in order to assess ecosystem health. An index of land use, water, and habitat quality (ILWHQ) was calculated to evaluate the environmental quality at the studied sites. The five least deteriorated sites (ILWHQ < 2; T13, T15, T16, T17, and T18) were selected as the reference sites. Seven of an initial 68 candidate metrics were selected using a stepwise procedure that evaluated metric stability, responsiveness to environmental variables, and redundancy. The selected metrics included number of Cyprinidae species, the proportion of individuals as benthic species, the proportion of omnivore species, the proportion of individuals as tolerant species, the proportion of demersal egg species, number of EPT (Ephemeroptera, Plectopera, and Trichoptera) taxa, and the proportion of clingers. The ration scoring method was used to score the seven metrics and four classes were defined to describe the ecosystem health of the Huntai River basin. The findings that the final multimetric index was negatively correlated with the ILWHQ and successfully differentiated reference from impaired condition indicated that the index should be useful for evaluating river conditions. According to the results, more than half of the sites (57.4%) were classified as poor or very poor. The ecosystem health in the Taizi River was better than that in the Hun River. Furthermore, testing with additional data is needed to assess the suitability and robustness of the index.