Possible routes for U. major larvae from South Korea, China and Russia to Lake Notoro and Matsukawa-ura. The warm currents are denoted by red dotted arrows, while the cold currents are denoted by blue dotted arrows. The collection sites of specimens from Korea and China used in this study are indicated by green circles, while the localities of U. major in Russia are denoted by yellow circles (The exact collection site in Sakhalin Island is unknown). Furthermore, potential dispersal routes of U. major larvae from South Korean/Chinese specimens and Russian specimens are shown in green and yellow arrows, respectively. SC: Soya Current, TC: Tsugaru Current, YSC: Yellow Sea Current, YSCC: Yellow Sea Counter Current, VS: Vladivostok, VB: Vostok Bay, OB: Olga Bay, SH: Sakhalin Island.