The Greenland halibut or Greenland turbot (Reinhardtius hippoglossoides) belongs to the Pleuronectidae family (the right eye flounders), and is the only species of the genus Reinhardtius. It is a deep water fish, ranging between about 200 and 1,600 m (700 and 5,200 ft), and is found in the northern Atlantic and northern Pacific Oceans. It has a variety of other English vernacular names including black halibut, blue halibut, lesser halibut and Newfoundland turbot.
The Greenland halibut is a flatfish, and the left eye has migrated during the fish's development so that it is on the right side of the head. However, in this fish, it has not moved as far as in bottom-dwelling flatfish and the fish can probably see forwards. The Greenland halibut can swim in a vertical position and both sides of its body are a speckled brown colour, but the left side is rather paler than the right. This fish is used for human consumption and is caught mostly by trawling. Greenpeace considers the fishery unsustainable and has added the Greenland halibut to its seafood red list.
Its morphology with the left eye positioned on the dorsal ridge of the forehead gives it an appearance of a cyclops when looking straight at it. The central position of the left eye in the Greenland halibut probably gives it a much wider range of peripheral vision in comparison to other flatfish where the eye has migrated completely. The body shape is elongated and compressed dorsal-ventrally and muscles on both sides are equally developed. Both sides are pigmented; however the left blind side is slightly lighter in color than the right side. The maximum length is about 120 cm and the maximum weight is about 45 kg, the normal length is 80–100 cm and they usually weigh 11–25 kg.
Its physical appearance suggests it to be a vigorous swimmer that can swim in a vertical position. Vertical swimming has been observed during tagging experiments. However, video analyzing of Greenland halibut behavior in front of a bottom trawl showed no sign of swimming in a vertical position. Even though most Greenland halibut are caught in bottom fishing gears (trawl, longline and gillnet) they have also been caught in surface drift nets which indicates that they can have a pelagic occurrence. Stomach analysis has also shown that the diet consists mostly of pelagic or bathypelagic organisms. Even though the Greenland halibut is a flatfish it does at times behave more like a roundfish.
It is a deepwater fish distributed mostly from 200 to 1600 m, but has been caught in deeper depths of 2,200 m (7,200 ft). It is mainly found in waters with temperatures from 1-4 °C, but has also observed at sub-zero temperatures down to -2.1 °C. It has a circumpolar distribution in the Northern Hemisphere and is found in both the North Atlantic and the North Pacific oceans. In the North Pacific it ranges from the Sea of Japan near Honshu northwards to the Chukchi Sea, east through the Aleutian Islands, and south as far as northern Baja California in Mexico. In the North Atlantic it occurs from England to northern Norway, Iceland and eastern Greenland in the east and from Newfoundland to north-western Greenland in the west.
Habitat and biology
The Greenland halibut is an arctic species which is found at depths of 200–2000 m, mainly between 500m and 1000m. However, it is often caught pelagically and it is thought that it swims on its ventral edge rather than on the blind side. It is an active, mid-water predator which feeds on prawns, fish such as Atlantic cod, Artic cod, eelpouts, capelin and redfish), and squid. It spawns at depths of 700–1500 m during spring and summer, from April to July at temperatures of 3-5 °C. Its eggs, larvae, and postlarvae are free-floating in deep water. The larvae complete their metamorphosis on attaining a length of 6-8.5 cm; the young fish tend to occur in the shallower areas than the adults.
In 2010, Greenpeace International has added the Greenland halibut to its seafood red list. "The Greenpeace International seafood red list is a list of fish that are commonly sold in supermarkets around the world, and which have a very high risk of being sourced from unsustainable fisheries. Although in 2017 the Marine Stewardship Council certified that the fishery for Greenland halibut was sustainable. This species is mainly caught using long lines. The meat is regarded as inferior to that of the Atlantic halibut and it is marketed fresh or frozen and is normally consumed either steamed or fried. In 1999 the total landings reported to the Food and Agriculture Organisation was 115,326 tonnes. The largest catches were reported from Greenland (34,481 t) and Norway (18,810 t). In 2001 1.078 tonnes were landed in Scotland with a value estimated at £1,885,000 but the Scottish Government reports that 33% of the catch is lost as the species has thick skin, high fat content and a low meat yield.
- Munroe, T.; Costa, M.; Nielsen, J.; Herrera, J. & de Sola, L. (2015). "Reinhardtius hippoglossoides". The IUCN Red List of Threatened Species: e.T18227054A45790364. Downloaded on 26 March 2018.
- Froese, Rainer and Pauly, Daniel, eds. (2018). "Reinhardtius hippoglossoides" in FishBase. February 2018 version.
- "Reinhardtius hippoglossoides (Walbaum, 1792)". FAO Specie Factsheets. Food and Agriculture Organisation Fisheries and Aquaculture Department. Retrieved 26 March 2018.
- "Greenland Halibut". Partner Seafood. Retrieved 26 March 2018.
- Greenpeace International Seafood Red list
- "Arctic Greenland halibut certified as sustainable". Marine Stewardship Council. 31 October 2017. Retrieved 26 March 2018.
- "Greenland Halibut". Scottish Government. Retrieved 26 March 2018.