A new threespine stickleback, Gasterosteus nipponicus sp. nov. (Teleostei: Gasterosteidae), from the Japan Sea region

Gasterosteus nipponicus sp. nov. is described from the holotype, 35 paratypes, and 60 additional specimens. The species differs from congeners in the following combination of characters: lateral plates complete, abruptly reducing in size above the anus, depth of lateral plate above the anus < 60 % that of the deepest plate; caudal keels thin, membranous. The new species is distributed in coastal Japan facing the Sea of Japan from Kyushu to Hokkaido Islands, along the Pacific coast of northern Japan from the Chiba Prefecture to Hokkaido, along the Sea of Okhotsk of Hokkaido, west to the southern and eastern coasts of Korean Peninsula, the Maritime Territory and north to Sakhalin Island, Russia.