Key signals
Combined survey biomass has been relatively stable since before 2003 when it was substantially higher.
Recruitment has been low in recent decades but increased substantially in 2022 and has been high since.
Length distributions from surveys show long term trends where average size is a little higher during periods of low recruitment.
Spawning stock biomass has been low for the past 30 years, compared with the years before, but above \(B_{lim}\) for the whole period according to the current assessment.
Fishing mortality (F) is above \(F_{MSY}\) but below \(F_{pa}\) and \(F_{lim}\) since 2013.
Age reading in this species is difficult and to date only the Marine and Freshwater Research Institute has read otoliths from catches in Icelandic waters, where approximately 60% of the catch occurs.
General information
Greenland halibut in ICES Subareas 5, 6 12 and 14 (East-Greenland, Iceland, Faroe-islands) are assessed as one stock. In Icelandic waters, it is found on the continental shelf around Iceland with the highest abundance west, north and east off the coast in deeper and colder waters. It is mainly found on a muddy substrate at depths ranging from 200-1500 m. The main spawning grounds are located west off the coast at around 1000 m depth and eggs and larvae drift between Iceland and the east coast of Greenland until juveniles seek bottom post metamorphosis. After spawning, Greenland halibut migrates further north and east to their main feeding grounds. No juvenile grounds are known within the assessment area, and migration is known to occur from adjacent management units.
In the water East of Greenland it is mainly found at depths greater than 600 m on the steep continental slope where as in the Faroe Islands it is mainly found North and East of the islands at 200 to 600 m.
Fishery
Landing trends
In 1980–1990, about 75–90% of catches were caught by Iceland ( Figure 1). Since 1990, the Icelandic proportion has decreased, and has in recent years been 50–60%. Highest catches were recorded in 1986, about 60 thous. tonnes. Landings in Icelandic waters (usually allocated to Division 5a) have historically been predominated by the total landings in areas 5+14 (Icelandic waters), but since the mid-1990s fisheries in Subarea 14 and Division 5b have developed. Landings have since 1997 been between 18-31 thous. tonnes, the recent year being the lowest (Figure 2).
Demersal trawl has been the main fishing gear for Greenland halibut in Icelandic waters, followed by gillnets, while a small proportion of the catch is taken on longlines and in shrimp trawls. Since 2015, landings by gillnets have, however, increased, reaching a high point of 62% of total catch in 2019 (Figure 3). The Greenland halibut trawl fishery is considered clean with respect to by-catches. The mandatory use of sorting grids in the shrimp fishery in Icelandic and Greenland waters since 2002 is observed to have reduced by-catches of Greenland halibut considerably. Greenland halibut is caught in relatively deep waters, with most of the catch (70%) taken between 400-800 meters depth. In 2003, most of Greenland halibut was caught at 800 meters or deeper (73%), but since then, catch has increased steadily in more shallow waters (Figure 4). Changes in depth range where Greenland halibut was caught seem to be reasonably synchronized with changes in fleet and therefore gear structure that target Greenland halibut in most recent years (Figure 3 and Figure 4).
Spatial distribution of the 2025 fishery and historic catch and effort in the trawl fishery in Subareas 5, 6, 12 and 14 is provided in Figure 5 and Figure 6. Fishery in the entire area did in the past occur in a seemingly continuous belt on the continental slope from the slope of the Faroe plateau to southeast of Iceland extending north and west of Iceland and further south to southeast Greenland. Fishing depth ranges from 350-500 m southeast, east and north of Iceland to about 1500 m at East Greenland.
In 2001–2008 a directed and a by-catch fishery by Spain, France, Lithuania, UK and Norway developed in the Hatton Bank area of Division 6.b, however, most of these fisheries ceased after 2008. Presently UK and France have a small fishery in the area. All catches in Subareas 6 and 12 are assumed to derive from the fishing on Hatton Bank area.
The number of vessels accounting for 95% of the catch of Greenland halibut in Icelandic waters changed from about 75 vessels in 1994-1998 to 14 in 2025 (Figure 7). This change coincided with reduced catches. Since 1998, the number of vessels accounting for 95% of the catch has been relatively constant despite variable annual catches, with the lowest number of vessels observed in the most recent year.
Catch per unit of effort from commercial fisheries
Estimates of catch per unit effort (CPUE) for the Icelandic trawl fleet directed at Greenland halibut for the period 1985–onwards is provided in Figure 8. The overall CPUE index for the Icelandic fishery is compiled as the average of the standardized indices from the whole area. Catch rates of Icelandic bottom trawlers decreased for all fishing grounds during 1990–1996 but peaked again in 2001. Since 2003, CPUE has been relatively stable. The CPUE index served as the primary basis for the stock assessment for many years until the assessment method was changed at the benchmark (WKBNORTH 2023). CPUE from Greenlandic and Faroese waters has not been included in the assessment as the model could not accommodate such disparate time series.
An analysis of the CPUE by area is shown in Figure 9. The CPUE west of Iceland showed a substantial drop in the period but after that the CPUE in the western area followed similar trends as other areas around Iceland.
Landings and discards
The Greenland halibut trawl fishery is mostly a clean fishery with little by-catches that mainly consist of beaked redfish and cod. Southeast of Iceland the cod fishery and a minor Greenland halibut fishery coincide spatially. In East Greenland where fishery is located on the steep slope, fishing grounds for cod and redfish are close to the Greenland halibut fishing grounds, but nevertheless the catches from single hauls are clean catches of Greenland halibut.
The mandatory use of sorting grids in the shrimp fishery in Iceland since the late 1980s and in Greenland since 2002 was observed to have reduced by-catches considerably. Based on few samples in 2006–2007, scientific staff observed by-catches of Greenland halibut to be less than 1% compared to about 50% by weight observed before the implementation of sorting grids (Sünksen, 2007). No information has since been available but the fishery in Division 14b generally report discard rates less than 1% by weight in logbooks.
Data and sampling
Commercial data
In general sampling is considered good from commercial catches in Icelandic waters from the main gears (gillnets, longlines and trawls). The sampling does seem to cover the spatial and seasonal distribution of catches except for long line (see Figure 11 and Figure 10). In 2020 sampling effort was reduced substantially, on-board sampling in particular, due to the COVID-19 pandemic. This reduction in sampling is, however, considered not to substantially affect the assessment of the stock in the short term. Sampling effort has now started to increase though no samples were optained from the Icelandic gillnet and long line fishery in 2025.