Abstract: Fishes are an important component of aquatic ecosystems. Fish diversity and its conservation are of considerable importance in regional ecological protection and sustainable development. In September and November 2022, we investigated fish communities across 10 fixed sampling sites that were set up at both Yuandang Lake and Dalian Lake in the Eco-green Integrated Development Demonstration Zone of Yangtze River Delta (hereafter the Demonstration Zone). Eighteen fish species were collected in Yuandang Lake, belonging to six families and six orders. Coilia ectenes and Erythroculter alburnus (IRI>20) were dominant species, while Rhinogobius giurinus was sub-dominant species (20>IRI>10). Seventeen fish species were collected in Dalian Lake, belonging to six families and six orders. The dominant species in Dalian Lake was Carassius auratus (IRI>20). Acheilognathus taenianalis and Rhinogobius giurinus were sub-dominant species (20>IRI>10). Yuandang Lake was dominated by the upper, carnivorous, and river-sea migratory fishes in terms of abundance and biomass. Dalian Lake was dominated by upper and sedentary fishes in terms of abundance and biomass, while omnivorous fishes dominated in terms of abundance, and planktivorous fishes dominated in terms of biomass. The Margalef species richness index (D) and Shannon diversity index (H) in Yuandang Lake were significantly lower than those of Dalian Lake (P<0.05). The Pielou evenness index (J) was not different between Yuandang Lake and Dalian Lake (P>0.05). The dominant fish species and ecological types were different among Yuandang Lake, Dalian Lake, and other water systems in the Dianshan Lake group. The diversity and composition of fish communities were affected by anthropogenic activities (fishery harvesting, fish stocking and releasing, and construction) and fish biology and environmental factors (water level, water quality, hydrological connectivity, and local habitat complexity). We suggest that multiple nets and seasonal continuous monitoring should be engaged in the surveys, and that the intensity of stocking and releasing and fishery harvesting should be effectively coordinated to ensure the stability of fish community and lake ecosystem in the Demonstration Zone. To promote sustainable development of the ecological conditions in the Demonstration Zone, ecological construction should be strengthened and human activities should be guided.

Key words: Eco-green Integrated Development Demonstration Zone of Yangtze River Delta, Yuandang Lake, Dalian Lake, fish community, species diversity