Topic: Northeast Arctic Greenland halibut

Mark-recapture studies, modelling work, and genetic studies suggest that the current division of populations may not be correct. Researchers from Norway, Canada, Iceland, Greenland, and the Faroe Islands are now collaborating to gain a better understanding of the population structure of Greenland halibut.

The area north and east of Svalbard to Kvitøya and Franz Josef Land is a nursery area for Greenland halibut. As they grow, they migrate southward into the Barents Sea. Mature Greenland halibut migrate to the continental shelf edge between mainland Norway and Svalbard and remain there year-round.

Spawning

The main spawning area is located to the upper edge of the continental shelf north and south of Bear Island. NEA Greenland halibut primarily spawn in deep water (500–800 m) during autumn and winter at the shelf edge between 70 and 75°N. Eggs and larvae drift with the currents depending on where the spawning takes place. During the last decade, most eggs and larvae have been carried north along Svalbard and east towards Franz Josef Land. 

Towards the end of summer and early autumn, young Greenland halibut begin to settle in the bottom sediments. The length is then approx. 6–7 cm. This occurs after a relatively long pelagic phase (8-10 months) during which larvae are spread throughout a large area to boundaries of the population. During the first 3–4 years, the Greenland halibut remain at or near the area where they settled to the bottom, usually in relatively shallow water (100–300 m). As they mature, they expand beyond their juvenile grounds toward the edge of the continental shelf and into deeper parts of the Barents Sea.

Diet

More than 40 different prey categories are found in the stomachs of Greenland halibut, but the dominant prey species are capelin, Polar cod, squid, shrimp and waste from fishing boats. As the size of predatory Greenland halibut increases, the proportion of smaller prey groups (shrimp and capelin) decreases, and the proportion of cod, haddock and fishing boat waste increases. There is little to suggest that Greenland halibut is subject to high grazing pressure. Young fish are only found in the stomachs of three species (Greenland shark, cod and the halibut itself). However, marine mammals such as seals and whales may be important predators on halibut.

Status

In the 1970s, the stock experienced a drastic decline, leading to the introduction of quota regulations in 1977. Norwegian quotas were significantly reduced from 40,000 tonnes in 1978 to 14,000 tonnes in 1980. The stock continued to decline, and in 1992, fishing for Greenland halibut was banned, except for research fishing and limited Norwegian coastal fishing. After this moratorium, the stock began to recover. When the moratorium was lifted, total catches increased significantly; from around 13,000 tonnes in 2009 to around 29,000 tonnes in 2019. This sharp increase in catches led to the stock beginning to decline again after 2014. Both the total stock and spawning biomass are now decreasing, and the spawning stock is now below the precautionary level.

The future stock development of Greenland halibut also depends on recruitment, which varies, with peaks in certain years. A good year class can have a significant impact on the stock development of Greenland halibut. The last recorded good year class is from 2017, and these are now entering the fisheries.