Fisheries are meant to influence the ecosystem by removing sustainable quantities of fish as food for humans. The fishery is, however, not considered sustainable if it impairs the recruitment of the fish stocks. Single species management often focuses on measuring the status of the fishery in relation to benchmarks called biological reference points (BRPs). The harvest rate and fishing pattern should hence fit with these biological requirements.
The exploitation of Northeast Arctic cod, haddock and saithe since 2000 have been sustainable and has not influenced the ecosystem negatively by impairing the recruitment. It can be concluded that the current fishery of golden redfish is too high and may have a negative influence on the ecosystem and the stock itself. After many years of overexploitation of the Greenland halibut stock the current exploitation seems to be sustainable and hence not influencing the ecosystem negatively.
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 in specimens close to, but below the minimum landing size. The lack of discard estimates leads to less precise and accurate stock assessments, and the influence of the fishery on the ecosystem is hence less understood.
In order to conclude on the total impact of trawling, an extensive mapping of fishing effort and bottom habitat would be necessary. In general, the response of benthic organisms to disturbance differs with substrate, depth, gear, and type of organism. The most serious effects of otter trawling have been demonstrated for hard-bottom habitats dominated by large sessile fauna, where erected organisms such as sponges, anthozoans and corals have been shown to decrease considerably in abundance in the pass of the ground gear. Barents Sea hard bottom substrata, with associated attached large epifauna should therefore be identified. Effects on soft bottom have been less studied, and consequently there are large uncertainties associated with what any effects of fisheries on these habitats might be.
Lost gears such as gillnets may continue to fish for a long time (ghost fishing). The catch efficiency of lost gillnets has been examined for some species and areas, but at present no estimate of the total effect is available. Other types of fishery-induced mortality include burst net, and mortality caused by contact with active fishing gear, such as escape mortality.
Work is currently going on jointly between Norway and Russia, exploring the possibility of using pelagic trawls when targeting demersal fish. The purpose is to avoid impact on bottom fauna and to reduce the mixture of other species. It will be mandatory to use sorting grids to avoid catches of undersized fish.