East Tsushima Strait

The eastern Tsushima Strait lies in the southern gateway to the Sea of Japan, where the Korea Strait divides around Tsushima Island. Its eastern channel is one of the shallow passages through which the Pacific and neighbouring seas exchange water with the nearly enclosed basin. The Sea of Japan is bounded by the Japanese archipelago, Sakhalin, the Korean Peninsula and the Russian Far East. Because the exits are narrow and generally no deeper than about 100 metres, exchange is restricted, tides are small and salinity is slightly lower than in the open ocean. The opening is nevertheless the sea's chief intake. Roughly 97 percent of its water inflow enters through the Korea Strait. Between October and April, outflow exceeds inflow because less water arrives through that gateway; the balance reverses from May through September. The warm, relatively saline Tsushima Current carries subtropical water northward and begins the sea's counterclockwise circulation. It later feeds the outflow through the Tsugaru and La Pérouse straits. This circulation, together with high dissolved oxygen, supports more than 800 aquatic plant species and some 3,500 animal species, including roughly 1,000 fishes and 26 mammals.

Fishing has long been the dominant maritime activity, focusing on species such as herring, sardines, squid and salmon. The sea shielded the Japanese islands from land invasion, notably by the Mongols, while carrying Asian traffic and, from the eighteenth century, European voyages.