Multi-Scale Assessment of Water Ecological Health Based on Fish and Benthic Indices of Biotic Integrity in the Three Gorges Dam Reservoir River Basin

Due to the destruction of natural aquatic ecosystems, developing comprehensive biological index evaluation methods is critical for river restoration and regeneration. However, research on spatial multiple-scale biological assessments remains lacking. This study used the biological integrity index methodology to examine the effectiveness of fish and macrobenthos in ecological assessments, as well as to analyze environmental factors impacting aquatic ecosystem health assessments. The Daning River basin in Chongqing was selected as the study area, and aquatic ecosystem health assessments were conducted at both regional and local scales. The results indicated that benthos were more abundant than fish, but there were no significant differences in species richness between sub-basins (p > 0.05). The assessment results for F-IBI and B-IBI showed partial discrepancies at the local fine-scale level but were nearly consistent at the regional broad-scale sub-basin level, with only small differences between the F-IBI and B-IBI ratings in one sub-basin. This discrepancy may be due to the diverse water environment. Woodland areas have significant negative relationships with F-IBI, while water areas have significant positive relationships with it. Comprehensively, the assessment findings of F-IBI beat those of B-IBI, implying that F-IBI may be better suited for regional assessments. However, the impact of local water quality issues remains unclear. To enhance ecological restoration, it is vital to conduct additional research into the degree of interference caused by water quality variables.