Tusk is abundant around Iceland and the Faroe Islands and in the deeper parts of the North Sea and Skagerrak. It is also common in the northwest Atlantic, off Greenland, and along the Reykjanes Ridge.
Spawning is widespread. The age of first maturation is eight to ten yrs, but varies within its geographic range. Maximum age: uncertain, but exceeding 20 years, Maximum length: about 100 cm. Maximum weight: about nine kg.
It is likely that several populations or “stocks” are found within its wide distribution area, but currently there is insufficient evidence to delineate populations. Very little is known about migrations. The species does not seem to form aggregations, e.g., during spawning or wintertime.
Fishery
Tusk has been exploited for centuries over most of its range, often taken as a by-catch species in other directed fisheries.
The average catch of tusk from 1988 to 2004 was 31 thousand tonnes. In this period the Norwegian catch was between 60 to 70 % of the total catch. The total catch in 2004 was 19 thousand tonnes. In Norway, around 85 % is taken by long liners, 10 % in gill nets and the remainder by a variety of other gears. The number of long liners (up to 21meter) participating in the fishery has decreased considerably recently; from 72 vessels in 2000 to 43 vessels in 2004.
Regulations and by-catches
No overall total allowable catch for the entire range of the species is set, so regulation is national or bilateral. The Norwegian fisheries in the EU, Faroe and Iceland Economic Zones are regulated by quotas. In Norwegian waters, the fishery is not regulated. In 2005, the Norwegian quota in the EU zone was four thousand tonnes, in the Faroese zone 1800 tonnes, and in the Icelandic zone 500 tonnes of ling and tusk combined.
Tusk is a secondary species in the long line fishery for ling, and otherwise a by-catch in mixed trawl fisheries. When tusk is abundant, common by-catches are other sub-arctic species such as rough head grenadier .On western grounds, there is a significant by-catch of deep-water sharks.
Stock status and setting of quotas
In 2004, ICES regarded the state of the tusk “stock” to be unknown. Based on historical catch per unit of effort showing a continuous decline to a low level, and the continued lack of sufficient data to carry out satisfactory assessments, a precautionary recommendation was to reduce the effort by 30 % compared to the 1998 level.