The fourhorn sculpin (Myoxocephalus quadricornis or Triglopsis quadricornis) is a species of fish in the Cottidae family. It is a demersal fish distributed mainly in brackish arctic coastal waters in Canada, Greenland, Russia, and Alaska, and also as a relict in the boreal Baltic Sea. There are also freshwater populations in the lakes of Norway, Sweden, Finland and Karelia (NW Russia) and in Arctic Canada (Nunavut and Northwest Territories).
The deepwater sculpin Myoxocephalus thompsonii of continental North American freshwater lakes (e.g., the Great Lakes) is closely related to the fourhorn sculpin and alternatively considered as a subspecies of the latter, Myoxocephalus quadricornis thompsonii.
The fourhorn sculpin has a large knobbly head with protruding lips and four bony protuberances, though the latter are not present in freshwater, lake forms of this fish. The pectoral fins are large and rounded. Freshwater forms resemble the Alpine bullhead and European bullhead but can be distinguished from them by the fact that the dorsal and anal fins terminate further forward giving a greater length to the caudal peduncle. The head, body and fins are brownish, mottled and barred with darker colour. The belly of the male is yellowish-brown while that of the female is whitish. In the sea this fish reaches 20 to 30 cm (8 to 12 in) but in lakes it seldom exceeds 15 cm (6 in).
The fourhorn sculpin feeds on bottom-dwelling invertebrates and fish eggs. It breeds in winter between November and March and the male tends the eggs. He digs a hollow in the substrate into which the female lays a batch of eggs. He then remains on guard, fanning the eggs with his fins throughout the hundred-day incubation period.
- "Fourhorn sculpin: Triglopsis quadricornis". NatureGate. Retrieved 2013-12-17.
- COSEWIC Assessment and Update Status Report on the Fourhorn Sculpin Myoxocephalus quadricornis Freshwater form in Canada. Committee on the Status of Endangered Wildlife in Canada. 2003.
- Gimenez Dixon, M. 1996. Triglopsis quadricornis. 2006 IUCN Red List of Threatened Species. Downloaded on 4 August 2007.
- Fourhorn sculpin Game and Fisheries Research.