Sample collection and processing
All fish samples were collected by nets and cages with the help of local fisherman during October to December 2019. Each fish sample was identified to the species level according to Chen (1998), Yue (2000), Chu (1999), and Fishbase (Froese & Pauly, 2018).
A total of 2157 individuals were collected, representing 57 fish species belonging to 13 families and 10 orders (Supplement Appendix 1). After preserving an appropriate amount of muscle tissue in 95% alcohol for molecular analysis, the whole body was fixed in 10% formalin and deposited in the Institute of Hydrobiology, Chinese Academy of Sciences.
For stable isotope analysis, white dorsal muscle was collected and rinsed with distilled water. The cleaned muscle was dried to a constant weight in an oven at 60 ℃ for at least 48 h and homogenized to powder by an automatic grinder, which was finally stored in clean centrifuged tubes until analysis.