The level of discarding in the fisheries is not known, and no discards are accounted for in the assessments. Discarding is known to be a (varying) problem, e.g., in the haddock fisheries where discards is highly related to the abundance of haddock close to, but below the minimum legal catch size. Dingsør (2001) estimated discards in the commercial trawl fishery for Northeast Arctic cod during 1946-1998 and the effects on the assessment, and Sokolov (2004) estimated cod discard in the Russian bottom trawl fishery in the Barents Sea in 1983-2002.
The lack of discard estimates leads to less precise and accurate stock assessments, and the influence of the fishery on the ecosystem is hence not fully understood.
Registration of redfish (dominated by S. mentella) taken as bycatch and discarded in the Norwegian shrimp fishery in the Barents Sea since 1984 show that shrimp trawlers removed significant numbers of juvenile redfish during the beginning of the 1980’s. peaking in 1985 when by-catches amounted to about 200 million individuals. As sorting grid became mandatory in 1993, by-catches of redfish reduced drastically during the 1990’s. The results also show that closure of areas is necessary to protect the smallest redfish juveniles since these are not sufficiently protected by the sorting grid. The by-catch and discard of cod mainly consists of 1- and 2-year-olds, but is generally small compared to other reported sources of mortality like catches, discards in the groundfish fisheries and cannibalism.
Noticeable discards of cod occurred in 1985, 1992 and 1998. The highest recorded numbers of cod was in 1985 (92 millions). The cod by-catches have declined in recent years (< 3 millions). Discards of haddock and Greenland halibut in the Barents Sea shrimp fishery have been estimated for the period 2000-2005, and show the highest discard in 2002 and 2000 for haddock (9.2 millions) and Greenland halibut (13.2 millions), respectively. For both species the discard in the shrimp fisheries has been low in the most recent years.