Diversity Patterns and Environmental Drivers of Bivalve Communities in the Caizi Lake Group and Its Major Tributaries During the Initial Post-Fishing Ban Period

To characterize freshwater bivalve communities and their environmental drivers in the Caizi Lake water system following the 10-year fishing ban in Yangtze River, this study three rounds of standardized surveys across hydrological periods in 2024—May (normal-water), September (high-water), and November (low-water). The results recorded 22 freshwater bivalve species belonging to 15 genera and 4 families. Notably, Ptychorhynchus pfisteri and the second-class national key protected wild animals in China, Lamprotula leaii and Uninovaculina chinensis, were first recorded in the Caizi Lake water system. Community composition was partitioned into three subgroups: Group I—Dasha River, Guache River, Longmian River, and Kongcheng River; Group II—the lake area; and Group III—Chang River. Biomass, density, and dominant species exhibited pronounced spatial heterogeneity, and the assemblage reflected a state of moderate disturbance. Redundancy analysis indicated that the variables that contribute significantly to species richness in sequence are the bitterling and suitable host fish, phytoplankton, and zooplankton. The research results reveal for the first time the population status and distribution patterns of bivalve resources in the Caizi Lake water system following the fishing ban. They not only provide a decision-making basis for the conservation and protection management of bivalve resources in the Caizi Lake water system but also offer data support for the assessment of the fishing ban effect and the evaluation of biological integrity in key waters of Anhui Province.