Amur stickleback

The Amur stickleback (Pungitius sinensis) is a species of fish in the family Gasterosteidae. This freshwater, brackish water, or marine benthopelagic fish is usually 6.5 cm (up to 9  cm) in length. It is widespread in East Asia: off the Korean peninsula, northeast and north China, Japan, the Kuril Islands, the Kamchatka peninsula, and the basin of the Amur River.