Map of sampling locations of Ctenopharyngodon idella. The abbreviations correspond to the sampling locations and are detailed in Table S1. The circled numbers indicate 12 river sections within the Pearl River (1, Beipanjiang; 2, Nanpanjiang; 3, Hongshuihe; 4, Lijiang; 5, Qianjiang; 6, Yujiang; 7, Xunjiang; 8, Mengjiang; 9, Hejiang; 10, Xijiang; 11, Beijiang; 12, Dongjiang). The red star and dashed line represent Dongta spawning ground and Changzhou dam, respectively.