FISH COMMUNITY STRUCTURE AND ITS SPATIOTEMPORAL DYNAMICS IN SUZHOU CREEK, SHANGHAI

Suzhou Creek has undergone extensive ecological rehabilitation over recent decades, yet systematic assessments of fish community recovery remain limited. To evaluate changes in fish diversity following remediation, we surveyed fish at 14sections of the creek in July (summer) and October (autumn) 2024 and analyzed species diversity and community structure across seasons and reaches. A total of 5845 individuals representing 55species, 45 genera, 19 families, and 9 orders were collected. Cypriniformes was the dominant order, comprising 63.6% of all species, followed by Perciformes (20.0%). The assemblage was dominated by omnivorous species (56.36%), pelagic and mid-water species (52.72%), and small-to medium-bodied fishes (61.81%). Species richness was 39 in upstream sections, 48 in tributary sections, and 30 in downstream sections. Dominant species varied with season and reach. Across the creek as a whole, Carassius auratus, Pseudorasbora parva, Acanthorhodeus chankaensis, and Culter dabryi were the dominant species. Margalef’s richness index (D), Pielou’s evenness index (J′), and the Shannon–Wiener diversity index (H′) were all higher in summer than those in autumn, whereas Simpson’s dominance index (C) showed the reverse pattern. Abundance–biomass comparison (ABC) curves indicated generally low disturbance across the fish community. W values in downstream sections were positive in both seasons (0.162 in summer; 0.124 in autumn), suggesting relatively stable community structure. Cluster analysis grouped the 14sections into three clusters, with a mean within-group similarity of 64.20% and between-group dissimilarities of 43.65%–48.55%. Compared with the 2019survey, total species richness increased from 45 to 55, and mean species richness per section increased from 17.3 to 22.0; the increase was most pronounced in downstream sections, where the mean rose from 10.0 to 18.8. The dominant species shifted from Pseudobrama simoni, C. auratus, and A. chankaensis in 2019 to C. auratus, A. chankaensis, P. parva, and C. dabryi in 2024, and fish communities in upstream and downstream sections became more similar in composition. Nevertheless, the low proportions of estuarine and herbivorous species indicate that Suzhou Creek remains a relatively isolated, highly channelized system with limited aquatic vegetation. Future restoration should prioritize improving hydrological connectivity and habitat heterogeneity, enhancing benthic substrate conditions, and re-establishing submerged macrophyte communities.