The state and trends of the Barents Sea ecosystem in 2018 - Summary

Snow crab (Chionoecetes opilio). Photo: Lidunn M. Boge © Nofima

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Summary Since the 1980s, the Barents Sea has gone from a situation with high fishing pressure, cold conditions and low demersal fish stock levels, to the current situation with high levels of demersal fish stocks, and warm conditions.

Ecosystem state: The ongoing warming were associated with increased water and air temperature, larger area covered by Atlantic (>3°C) and Mixed (0-3°C) warm water masses and decreased ice coverage both during winter and summer. The warming was also associated with increased primary and secondary (macro zooplankton such as krill and jellyfish) production, increased fish recruitment (age 0) which trigger positive development of fish stocks (cod, haddock, deep water redfish, capelin and herring). Increased production and adequate fishing pressure in relation to stock size led to cod and haddock stock size increasing to record high levels and the capelin stock withstanding the high predation level. Large fish stocks have distribution range extending further north, where feeding environmental conditions were suitable due to warming. The number of whales, which use the Barents Sea as summer feeding area, increased or stabilized in last decades. Several sea birds populations from coastal colonies stay or migrate in to the Barents Sea to feed and moult, possibly increasing the total number. Arctic fish and benthos communities showed opposite trends, decreased in numbers and distribution most likely due to increased predation and competition pressure from boreal species. A true arctic fish, polar cod, showed decreased of stock size and recruitment failure in the traditional area, the southeastern Barents Sea. Reduction of ice cover and warmer temperature condition in addition to increased predation from a large cod stock are some of reasons for the polar cod stock decrease.

Human pressure: The assessment for several commercial important stocks indicated that the stocks has been fished sustainably and has remained well above precautionary reference limits. The present (2016–2021) minke whale quota is considered precautious, conservative, and protective for the minke whale population in the Northeast Atlantic. Catches of harp seals in recent years have been much lower than the quotas. The AIS tracking of vessel in the Barents Sea in August, 2012 to 2018, indicated an increased fisheries effort east of Svalbard and also an increase in passenger vessels to the Svalbard area. The effect on the marine ecosystem of the increased tourist traffic is not known, but the possibility for more littering in a potential risk. Large-scale monitoring of marine litter since the 2010, showed that plastic dominated number of observations with marine litter, while textile, paper, rubber and metal was observed occasionally.

Expected changes in the coming years: Oceanic systems have a “longer memory” than atmospheric ones. According to the expert evaluation, the Atlantic water temperature in the Murman Current is expected to decline slightly but remain typical of warm years. Due to high temperatures and low sea-ice extent in recent years, the ice coverage of the Barents Sea is expected to remain below normal.

Most of the commercial fish stocks found in the Barents Sea stocks are at or above the long-term level. The exceptions are polar cod and Sebastes norvegicus. The shrimp abundance is relatively stable and above the long-term meanwhile, the abundance and distribution area of snow crab is increasing. Based on the current abundance and age structure of the main commercial stocks, the following lines of development are possible: a new haddock outburst may take place, as the 2016 and 2017 year classes so far seem to be of the same order of magnitude as the strong 2004–2006 year classes; the abundance of young herring is currently the highest since 2005, and this may affect the capelin recruitment in 2018–2019 negatively; the westward expansion of snow crab leads to higher overlap between cod and snow crab and thus predation by cod on snow crab may slow down in addition to higher temperatures the rate of increase of the snow crab stock. If the sea temperature increases further, this may allow further north and eastwards expansion of several stocks, while e.g. cod has almost reached it maximal distribution and polar cod will be negatively affected by other species moving into typical polar cod areas.

The WGIBAR group updated most of the time series data and established additional time series for the oceanographic conditions, meso-zooplankton and 0-group fish, based on WGIBAR-subareas for the Barents Sea. The WGIBAR working group provide knowledge of the status, changes, relationships, and processes in the ecosystems to the Joint Russian-Norwegian Fisheries Commission, the Joint Russian-Norwegian Environmental Commission, the Norwegian Ministry of Climate and Environment, Fisheries organizations, different ICES working groups and disseminate the results at scientific conference and by scientific and public papers.

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