Original ArticlesA pilot macroinvertebrate-based multimetric index (MMI-CS) for assessing the ecological status of the Chishui River basin, China

•Chishui River is the only undammed and nature river in China, not affected by dams and serious water pollution that commonly occurs in other rivers.•A pilot macroinvertebrate-based multi-metric index (MMI-CS) was established for assessing the ecological status of Chishui River basin, China.•Five ecological status ratings were set up and the results of evaluation showed the index was reasonable and effective.•Five ecological status ratings were set up and the results of evaluation showed the index was reasonable and effective.•The sites with higher ecological status were in the upper and middle reaches while the sites with lower ecological status were in the lower reaches.

As the only undammed river in the Yangtze River basin and an important rare fish reserve, the Chishui River has attracted the world's attention. It was recently selected as a reference river for a pilot biomonitoring assessment within the European Union-China River Basin Management Programme. As the outcome of the project, a pilot multimetric index (MMI-CS) was developed for future assessment of the ecological status of the Chishui River basin. In this study, eight core metrics were selected and used to build the multimetric system. These metrics included the total number of taxa (TotalTax), the number of taxa of sprawlers (SprwlTax), the number of intolerant taxa (IntolTax), the Hilsenhoff biotic index (HBI), the percentage of Ephemeroptera, Trichoptera and Plecoptera (EPTPct), the number of Ephemeroptera taxa (EphemTax), the percentage of collectors (CllctPct) and the average score per taxon (ASPT). Five ecological status ratings (“Excellent”, “Good”, “Fair”, “Poor” and “Very Poor”) were established. The results of the evaluation showed that the index was reasonable and effective. The results of the assessment showed that sites with higher ecological status were distributed mainly in the upper and middle reaches of the region and that sites with lower ecological status were centrally distributed in the lower reaches. Moreover, the index should be refined and validated using additional datasets obtained in different seasons in the future for routine bioassessment within the framework of sustainable management.