CHARACTERISTICS AND HISTORICAL CHANGES OF FISH COMMUNITY IN CAIZI LAKE DURING THE EARLY PERIOD OF THE “10-YEAR FISHING BAN”

Three surveys were conducted in July 2022 (summer), October 2022 (autumn) and May 2023 (spring) to understand the characteristics and historical changes of fish communities in Caizi Lake during the early period of the “10-year fishing ban”. The results showed that a total of 46 fish species belonging to 6 orders, 11 families and 36 genera, with Cyprinidae accounting for 63.04% of the total species. The main dominant species including 7species, i.e. Coilia brachygnathus, Toxabramis swinhonis, Culter dabryi, Hypophthalmichthys molitrix, Aristichthys nobilis, Pseudobrama simoni and Carassius auratus. According to the living habits, most species were resident fish (89.13%). In terms of spatial and nutritional niche, benthic and omnivorous fish were dominant, accounting for 39.13% and 41.30% of the total species, respectively. Significant differences in fish diversity indices were observed across the three seasons, with higher Shannon diversity index, Pielou evenness index, and Margalef richness indices in spring and autumn compared to summer. However, the Simpson dominance index in summer exceeded that in spring and autumn. NMDS and SIMPER analysis indicated that significant differences in the structure of fish communities between different seasons, with notable contributing species such as Coilia brachygnathus, Chanodichthys dabryi and Toxabramis swinhonis. RDA analysis showed that water depth, electrical conductivity, and chlorophyll a as key environmental factors affecting the fish community structure in Caizi Lake. Compared with historical data, the species number in this survey was much lower than that before 2001 and 2007—2008, yet it exhibited minimal variance from the count in 2017—2018. Besides, four fish species, including Megalobrama mantschuricus, Parabotia fasciata, Paramisgurnus dabryanus and Pelteobaggrus nitidus, were exclusively observed in this survey. Overall, the fish species number did not obviously increased in Caizi Lake during the early period of the “10-year fishing ban”, emphasizing the necessity for targeted measures and ongoing monitoring efforts.