Little is known about its population structure, but it is not unlikely that separate populations or “stocks” occur within its extensive distribution area. Spawning areas, and hence the distribution of eggs and larvae, are widespread. Demersal juveniles are found in quite shallow waters along the coast or on offshore banks, e.g. in the northern North Sea. The species does not seem to form aggregations, e.g. during spawning or during wintertime. Length at first spawning is 60 to 75cm (total length), and age at first spawning is five to seven years. Most ling in commercial catches are less than ten years old, but individuals of ages 19 to 20 years also occur. The maximum age in an unexploited population is probably higher, i.e. 30 years or more. Maximum weight: about 40 kg. Maximum length: about 200 cm.
Fishery
Ling has been exploited for centuries over most of its range. It is currently a by-catch in the trawl and gill net fisheries, but the major component of the landings stems from the long line fishery, either from the long liners that target ling, or from fisheries with other primary targets, e.g. cod or hake.
The average catch-per-year of ling from 1988 through 2004 was 44 thousand tonnes (in 2004 the catch was 32 thousand tonnes) and the Norwegian catches were approximately 40 % of the total catch. The Norwegian catch of ling was taken by: long liners (70 %), gill nets (25 %), and trawlers (5 %). The total number of long liners participating in the fishery has recently declined from 72 vessels (up to 21meter) in 2000 to 43 vessels in 2004.
Regulations and by-catches
No overall international total allowable catch is set for ling, but the fishery is to some extent regulated by bilateral quotas and other national measures. The Norwegian fishery is regulated by quotas in the EU-, Faroe, and Iceland Economic Zones. In the Norwegian Economic Zone, the fishery is not regulated. In 2005, the Norwegian quota for ling in EU waters was 6800 tonnes, in the Faroese zone the quota was 2200 tons (ling and blue ling), and in the Icelandic zone Norway could take a combined catch of 500 tonnes of ling and tusk.
Tusk is the predominant by-catch or secondary target species, but a range of other species is also taken. In many western areas, the greater fork-beard is a major by-catch.
Stock status and setting of quotas
In 2004, ICES considered the state of the “stock” to be unknown but probably varying within the large range of the species. Precautionary measures are recommended based on the catch per unit of effort (CPUE) and because it is currently not possible to carry out satisfactory analytical assessments due to lack of relevant data for most areas. In all subareas, except around Iceland, the CPUE has shown a downward trend since the early 1970s. A reduction of fishing effort by 30 % (referenced to the 1998 level) in order to reduce total mortality is recommended. The recommendation for The Faroe area is that effort should not be allowed to increase beyond the present level.