Halibut is the common name for three species of flatfish in the family of right-eye flounders. In some regions, and less commonly, other species of large flatfish are also referred to as halibut.
The word is derived from haly (holy) and butte (flat fish), for its popularity on Catholic holy days. Halibut are demersal fish and are highly regarded as a food fish as well as a sport fish.
Species A 2018 cladistic analysis based on genetics and morphology showed that the Greenland halibut diverged from a lineage that gave rise to the Atlantic and Pacific halibuts. The common ancestor of all three diverged from a lineage that gave rise to the genus Verasper, comprising the spotted halibut and barfin flounder.
Genus Hippoglossus Atlantic halibut, Hippoglossus hippoglossus – lives in the North Atlantic Pacific halibut, Hippoglossus stenolepis – lives in the North Pacific Ocean Genus Reinhardtius Greenland halibut, Reinhardtius hippoglossoides – lives in the cold northern Atlantic, northern Pacific, and Arctic Oceans
Physical characteristics The Pacific and Atlantic halibut are the world's largest flatfish, with debate over which grows larger.The National Marine Fisheries Service / NOAA, Pacific Halibut Paragraph one, "About the Species."The National Marine Fisheries Service / NOAA, Atlantic Halibut "Biology." Halibut are dark brown on the top side with a white to off-white underbelly and have very small scales, invisible to the naked eye, embedded in their skin.Pacific Halibut (Hippoglossus stenolepis), Alaska Department of Fish and Game. Adfg.state.ak.us. Retrieved 19 August 2012. Halibut are symmetrical at birth with one eye on each side of the head. Then, about six months later, during larval metamorphosis one eye migrates to the other side of the head. The eyes are permanently set once the skull is fully ossified. At the same time, the stationary-eyed side darkens to match the top side, while the other side remains white. This color scheme disguises halibut from above (blending with the ocean floor) and from below (blending into the light from the sky) and is known as countershading.
The IGFA size record for halibut was apparently broken off the waters of Norway in July 2013 by a , fish. This was awaiting certification as of 2013.515-Pound Halibut Caught By Marco Leibenow Near Norway May Be World Record Woods 'n Water Magazine, 19 August 2013. In July 2014, a Pacific halibut was caught in Glacier Bay, Alaska; this is, however, discounted from records because the halibut was shot and harpooned before being hauled aboard.
Diet Halibut feed on almost any fish or animal they can fit into their mouths. Juvenile halibut feed on small crustaceans and other bottom-dwelling organisms. Animals found in their stomachs include sand lance, octopus, crab, salmon, hermit crabs, lamprey, sculpin, cod, pollock, herring, and flounder, as well as other halibut. Halibut live at depths ranging from a few meters to hundreds of meters, and although they spend most of their time near the bottom, halibut may move up in the water column to feed. In most ecosystems, the halibut is near the top of the marine food chain. In the North Pacific, common predators are sea lions, killer whales, salmon sharks and humans.
Sex-determining genes Halibut species vary in sex determination systems. The Atlantic halibut went down a purely XX/XY route, with the male being heterogametic, around 0.9 to 3.8 million years ago. The sex-determining gene for the Atlantic halibut is likely to be gsdf on chromosome 13. The Pacific halibut went down a ZZ/ZW route, with the female being heterogametic, around 4.5 million years ago. The master sex-determining gene of the Pacific halibut is located on chromosome 9 and it is likely to be bmpr1ba. The gene sox2 is likely to play the same role in the Greenland halibut.
Halibut fishery The North Pacific commercial halibut fishery dates to the late 19th century and today is one of the region's largest and most lucrative. In Canadian and US waters, long-line fishing predominates, using chunks of octopus ("devilfish") or other bait on circle hooks attached at regular intervals to a weighted line that can extend for several miles across the bottom. The fishing vessel retrieves the line after several hours to a day. The effects of long-line gear on habitats are poorly understood, but could include disturbance of sediments, benthic structures, and other structures.
International management is thought to be necessary, because the species occupies waters of the United States, Canada, Russia, and possibly Japan (where the species is known to the Japanese as ohyo), and matures slowly. Halibut do not reproduce until age eight, when about long, so commercial capture below this length prevents breeding and is against US and Canadian regulations supporting sustainability. Pacific halibut fishing is managed by the International Pacific Halibut Commission.
For most of the modern era, halibut fishery operated as a derby. Regulators declared time slots when fishing was open (typically 24–48 hours at a time) and fishermen raced to catch as many pounds as they could within that interval. This approach accommodated unlimited participation in the fishery while allowing regulators to control the quantity of fish caught annually by controlling the number and timing of openings. However, it led to unsafe fishing, as openings were necessarily set before the weather was known, forcing fishermen to leave port regardless of the weather. These derbies also meant fresh halibut was only on the market during several different weeks distributed throughout the year where the surge in supply would limit the price that could be set, therefore diminishing the income of halibut fishermen.
Individual fishing quotas In 1995, US regulators allocated individual fishing quotas (IFQs) to existing fishery participants based on each vessel's documented historical catch. IFQs grant to holders a specific proportion of each year's total allowable catch (TAC). The fishing season is about eight months. The IFQ system improved both safety and product quality by providing a stable flow of fresh halibut to the marketplace. Critics of the program suggest, since holders can sell their quota and the fish are a public resource, the IFQ system gave a public resource to the private sector. The fisheries were managed through a treaty between the United States and Canada per recommendations of the International Pacific Halibut Commission, formed in 1923.
A significant sport fishery in Alaska and British Columbia has emerged, where halibut are prized game and food fish. Sport fisherman use large rods and reels with line, and often bait with herring, large jigs, or whole salmon heads. Halibut are strong and fight strenuously when exposed to air. Smaller fish will usually be pulled on board with a gaff and may be clubbed or even punched in the head to prevent them from thrashing around on the deck. In both commercial and sport fisheries, standard procedure is to shoot or otherwise subdue very large halibut over before landing them.
Overfishing and population decline
The Atlantic halibut has been a major target of fishing since the 1840s with overfishing causing the depletion of the species in the Georges Bank in 1850, then all the way up to the Canadian Arctic in 1866. In the 1940s the American fishing industry collapsed but the Canadian fishing industry remained until there was a decline in Canadian halibut fishery in the 1970s and 1980s. This allowed the halibut population to briefly rebound before collapsing in the 1990s. Since a low point in the early 2000s, the population has rebounded once again and may be stabilizing, but the species is not nearly as abundant in most locations as it was in the early 1800s.
Atlantic halibut population Currently, Atlantic halibut is managed as two stocks in Canadian waters, which are the Atlantic Continental Shelf stock and the Gulf of St. Lawrence stock.Kess, Tony; Einfeldt, Anthony L; Wringe, Brendan; Lehnert, Sarah J; Layton, Kara K S; McBride, Meghan C; Robert, Dominique; Fisher, Jonathan; Le Bris, Arnault; den Heyer, Cornelia; Shackell, Nancy; Ruzzante, Daniel E; Bentzen, Paul; Bradbury, Ian R (2021-10-09). Hauser, Lorenz (ed.). "A putative structural variant and environmental variation associated with genomic divergence across the Northwest Atlantic in Atlantic Halibut". ICES Journal of Marine Science. 78 (7): 2371–2384. doi:10.1093/icesjms/fsab061. ISSN 1054-3139 The Atlantic halibut has two other stocks in the Northwest Atlantic, those being the Gulf of Maine-Georges Bank stock controlled by the United States and one controlled by France near the Saint-Pierre and Miquelon Archipelago. The Georges Bank stock is still considered to be depleted and it is listed as a species of concern in the United States. In the two main populations of Atlantic halibut there are many subpopulations, but many have been lost due to patches of extreme overfishing and the populations remain depleted as a whole from what they were in the 1800s.
Pacific and Greenland halibut populations The Pacific halibut and Greenland halibut have not had this level of fragmentation, and their population is far larger in the United States' waters, with North Pacific halibut and groundfish fisheries extracting the largest volume of catch out of all United States fishery areas. Sometimes the California halibut is mistaken for a subspecies, but they are not, and are not even a true halibut species. In the North Atlantic, observation of migration indicates that there are only two major populations of Greenland halibut that both stretch vast distances. Those populations being the Northeast one stretching from the Kara Sea to Greenland, and the Northwest one stretching from Newfoundland to Baffin Bay.Vihtakari, Mikko; Elvarsson, Bjarki Þór; Treble, Margaret; Nogueira, Adriana; Hedges, Kevin; Hussey, Nigel E; Wheeland, Laura; Roy, Denis; Ofstad, Lise Helen; Hallfredsson, Elvar H; Barkley, Amanda; Estévez-Barcia, Daniel; Nygaard, Rasmus; Healey, Brian; Steingrund, Petur (2022-07-18). "Migration patterns of Greenland halibut in the North Atlantic revealed by a compiled mark–recapture dataset". ICES Journal of Marine Science. 79 (6): 1902–1917. doi:10.1093/icesjms/fsac127. ISSN 1054-3139. These stocks had been previously thought to be four different populations, but migration has indicated that they are only two different populations, and that fishing has not fragmented them. New research also indicates that the Greenland halibut originally came from the Pacific Ocean and spread into the Arctic Basin when the Bering Strait opened for a second time around 3 million years ago, and thus the Pacific halibut is its closest living relative.
Evolutionary diversification of fragmented populations