Editing Halibut (section)

==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 hook]]s 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 {{convert|30|in|cm|abbr=on|order=flip|-1}} 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. The approach led to unsafe fishing, as openings were necessarily set before the weather was known, forcing fishermen to leave port regardless of the weather. The approach limited fresh halibut to the markets to several weeks per year when the gluts would push down the price received by fishermen.{{citation needed|date=May 2017}}

===Individual fishing quotas===
In 1995, US regulators allocated [[individual fishing quota]]s (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 fishing|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 {{convert|80|-|150|lb|kg|round=5|abbr=on|adj=on|order=flip}} line, and often bait with [[herring]], large [[jigging|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 [[Fishing gaff|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 {{convert|150|-|200|lb|kg|round=5|abbr=on|order=flip}} before landing them.{{citation needed|date=August 2021}}

=== 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.<ref name="Shackell-2022">{{Cite journal |last1=Shackell |first1=Nancy L. |last2=Fisher |first2=Jonathan A. D. |last3=den Heyer |first3=Cornelia E. |last4=Hennen |first4=Daniel R. |last5=Seitz |first5=Andrew C. |last6=Le Bris |first6=Arnault |last7=Robert |first7=Dominique |last8=Kersula |first8=Michael E. |last9=Cadrin |first9=Steven X. |last10=McBride |first10=Richard S. |last11=McGuire |first11=Christopher H. |last12=Kess |first12=Tony |last13=Ransier |first13=Krista T. |last14=Liu |first14=Chang |last15=Czich |first15=Andrew |date=2022-07-03 |title=Spatial Ecology of Atlantic Halibut across the Northwest Atlantic: A Recovering Species in an Era of Climate Change |url=https://www.tandfonline.com/doi/full/10.1080/23308249.2021.1948502 |journal=Reviews in Fisheries Science & Aquaculture |language=en |volume=30 |issue=3 |pages=281–305 |doi=10.1080/23308249.2021.1948502 |bibcode=2022RvFSA..30..281S |s2cid=238800003 |issn=2330-8249|url-access=subscription }}</ref>

=== 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.<ref name="Kess">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 (identifier)|doi]]:10.1093/icesjms/fsab061. [[ISSN (identifier)|ISSN]] 1054-3139</ref> 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.<ref name="Shackell-2022" /> 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.<ref>{{Cite journal |last1=Baetscher |first1=Diana S. |last2=Beck |first2=Jessie |last3=Anderson |first3=Eric C. |last4=Ruegg |first4=Kristen |last5=Ramey |first5=Andrew M. |last6=Hatch |first6=Scott |last7=Nevins |first7=Hannah |last8=Fitzgerald |first8=Shannon M. |last9=Carlos Garza |first9=John |date=March 2022 |title=Genetic assignment of fisheries bycatch reveals disproportionate mortality among Alaska Northern Fulmar breeding colonies |journal=Evolutionary Applications |language=en |volume=15 |issue=3 |pages=447–458 |doi=10.1111/eva.13357 |issn=1752-4571 |pmc=8965376 |pmid=35386403|bibcode=2022EvApp..15..447B }}</ref><ref name="Wojtasik-2021">{{Cite journal |first1=Barbara |last1=Wojtasik |first2=Agnieszka |last2=Kijewska |first3=Monika |last3=Mioduchowska |first4=Barbara |last4=Mikuła |first5=Jerzy |last5=Sell |date=2021 |title=Temporal isolation between two strongly differentiated stocks of the Greenland halibut ( Reinhardtius hippoglossoides Walbaum, 1792) from the Western Barents Sea |journal=Polish Polar Research |pages=117–138 |doi=10.24425/ppr.2021.136603|doi-access=free |hdl=20.500.12128/21254 |hdl-access=free }}</ref> Sometimes the [[California halibut]] is mistaken for a subspecies, but they are not, and are not even a true halibut species.<ref>{{Cite journal |last1=Vargas-Peralta |first1=Carmen E. |last2=Farfán |first2=Claudia |last3=Cruz |first3=Fabiola Lafarga-De La |last4=Barón-Sevilla |first4=Benjamín |last5=Río-Portilla |first5=Miguel A. Del |date=2020-12-18 |title=Genoma mitocondrial completo del lenguado de California, Paralichthys californicus |url=https://cienciasmarinas.com.mx/index.php/cmarinas/article/view/3121 |journal=Ciencias Marinas |language=es |volume=46 |issue=4 |pages=297–306–297–306 |doi=10.7773/cm.v46i4.3121 |s2cid=234547077 |issn=2395-9053|doi-access=free }}</ref> 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.<ref>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 (identifier)|doi]]:10.1093/icesjms/fsac127. [[ISSN (identifier)|ISSN]] 1054-3139.</ref> 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.<ref>{{Cite journal |last1=Orlova |first1=S. Yu. |last2=Volkov |first2=A. A. |last3=Shcepetov |first3=D. M. |last4=Maznikova |first4=O. A. |last5=Chernova |first5=N. V. |last6=Chikurova |first6=E. A. |last7=Glebov |first7=I. I. |last8=Orlov |first8=A. M. |date=2019-01-01 |title=Inter- and Intra-Species Relationships of Greenland Halibut Reinhardtius hippoglossoides (Pleuronectidae) Based on the Analysis of Nuclear and Mitochondrial Genetic Markers |url=https://doi.org/10.1134/S0032945219010119 |journal=Journal of Ichthyology |language=en |volume=59 |issue=1 |pages=65–77 |doi=10.1134/S0032945219010119 |bibcode=2019JIch...59...65O |s2cid=255280804 |issn=1555-6425|url-access=subscription }}</ref>

=== Evolutionary diversification of fragmented populations ===
In the Atlantic halibut studies have shown that the Atlantic Continental Shelf stock and the Gulf of St. Lawrence stock have begun to differentiate genetically from each other due to low connectivity between populations, low rates of exchange, and subsequent adaptation to local environments. Some adaptations can show up as changes in life-history trait parameters, which can change on a faster time scale than evolution and cause behavioural segregation. This can occur even in areas with enough genetic mixing to prevent genetic divergence.<ref name="Shackell-2022" /><ref name="Kess" /> One small but significant observed adaptation difference in the Atlantic halibut has been that the fish in the warmer Scotian Shelf have a faster growth rate than the halibut in the colder southern Grand Banks.<ref name="Shackell-2022" /> The Pacific halibut population remains largely genetically homologous throughout their range, but there is some variation of life-history traits on a geographic gradient.<ref name="Shackell-2022" /> Despite its large range, the populations of Greenland halibut remain largely homogenous due to a lack of barriers for gene flow between its four major populations.<ref name="Wojtasik-2021" /> There are small differences between subpopulations due to differing environmental factors, such as salinity and temperature gradients, but not to the degree seen in Atlantic halibut, as gene flow and migration continues throughout many different stocks.