Pseudopleuronectes obscurus is a flatfish

Flatfish

The flatfish are an order of ray-finned fish, also called the Heterosomata, sometimes classified as a suborder of Perciformes. In many species, both eyes lie on one side of the head, one or the other migrating through and around the head during development...

 of the family Pleuronectidae

Pleuronectidae

Righteye flounders are a family, Pleuronectidae, of flounders. They are called "righteye flounders" because most species lie on the sea bottom on their left side, with both eyes on the right side. The Paralichthyidae are the opposite, with their eyes on the left side.Their dorsal and anal fins are...

. It is a demersal fish that lives on salt bottoms in the temperate waters of the northwestern Pacific

Pacific Ocean

The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...

, from Hokkaido

Hokkaido

, formerly known as Ezo, Yezo, Yeso, or Yesso, is Japan's second largest island; it is also the largest and northernmost of Japan's 47 prefectural-level subdivisions. The Tsugaru Strait separates Hokkaido from Honshu, although the two islands are connected by the underwater railway Seikan Tunnel...

 to the Kuril Islands

Kuril Islands

The Kuril Islands , in Russia's Sakhalin Oblast region, form a volcanic archipelago that stretches approximately northeast from Hokkaidō, Japan, to Kamchatka, Russia, separating the Sea of Okhotsk from the North Pacific Ocean. There are 56 islands and many more minor rocks. It consists of Greater...

, the Sea of Okhotsk

Sea of Okhotsk

The Sea of Okhotsk is a marginal sea of the western Pacific Ocean, lying between the Kamchatka Peninsula on the east, the Kuril Islands on the southeast, the island of Hokkaidō to the far south, the island of Sakhalin along the west, and a long stretch of eastern Siberian coast along the west and...

, Sakhalin

Sakhalin

Sakhalin or Saghalien, is a large island in the North Pacific, lying between 45°50' and 54°24' N.It is part of Russia, and is Russia's largest island, and is administered as part of Sakhalin Oblast...

 and the Tatar Strait to the northeastern coast of Korea

Korea

Korea ) is an East Asian geographic region that is currently divided into two separate sovereign states — North Korea and South Korea. Located on the Korean Peninsula, Korea is bordered by the People's Republic of China to the northwest, Russia to the northeast, and is separated from Japan to the...

 and the Yellow Sea

Yellow Sea

The Yellow Sea is the name given to the northern part of the East China Sea, which is a marginal sea of the Pacific Ocean. It is located between mainland China and the Korean Peninsula. Its name comes from the sand particles from Gobi Desert sand storms that turn the surface of the water golden...

. It can grow up to 56 centimetres (22 in) in length, though it more commonly reaches around 35 centimetres (13.8 in), and its maximum recorded weight is 2.6 kilograms (5.7 lb).