Map showing the geographic distributions of Anguilla japonica and A. marmorata. Map showing the geographic distributions of Anguilla japonica (thick gray lines on the coastlines) and A. marmorata (thick black lines on the coastlines) in East Asia and collection sites of samples analyzed in this study (white triangle, A. marmorata; white circle, A. japonica; Cheng and Tzeng 1996). General patterns of current systems in the western North Pacific and central Indonesian seas (adapted from Nitani 1972 and Lukas et al. 1991) and spawning grounds of A. japonica (gray circle with the letter J) and A. marmorata (black circle with the letter M) (Kuroki et al. 2009; Tsukamoto et al. 2011) are also shown. Sampling locations: Tungkang River (T) and Shuangshi River (S), Taiwan; Mingchiang River (M), Chyantarng River (C), and Yalu River (Y), China; Ichinomiya River (I), Japan; Cagayan River (P), the Philippines; Hsiukuluan River (H), Taiwan; and Kurio River (J), Japan. NEC, North Equatorial Current; KC, Kuroshio Current; OC, Oyashio Current; TS, Tsushima Current; CCC, China Coastal Current; SCSWC, South China Sea Warm Current; IK, Intruded Kuroshio; MC, Mindanao Current; NECC, North Equatorial Counter Current; SEC, South Equatorial Current.