The Biological Monitoring Working Party (BMWP) and Average Score Per Taxon (ASPT) indices, which rely on family-level environmental sensitivity values (FESVs), are widely used in freshwater bioassessment. However, regional differences in taxonomic composition often render existing FESV systems incomplete or incompatible, and the influence of rare families remains poorly understood. Using a historical dataset from the temperate Taizi River basin in Northeast China, we developed a regional FESV system for benthic macroinvertebrates. A total of 67 FESVs were established, including 10 families not previously scored in the UK system. These values followed a normal distribution and were ecologically validated using canonical correspondence analysis (CCA). Both BMWP and ASPT indices showed significant correlations with water quality parameters, the Water Quality Index (WQI), and the Habitat Quality Index (HQI). Notably, excluding rare families (occurrence frequency < 1%) did not reduce but slightly enhanced the responsiveness of both indices. CCA identified HQI, conductivity, and ammonia nitrogen as the primary drivers of community composition, and the inferred ecological preferences aligned well with the assigned FESVs. This study provides a robust, regionally adapted framework for family-level bioassessment in temperate East Asian rivers and supports the exclusion of rare taxa to improve cost-effectiveness and index sensitivity.
Xu et al. (Wed,) studied this question.