Status of the Barents Sea Ecosystem

Norwegian Institute of Marine Research
http://www.imr.no/filarkiv/havets_ressurser_og_miljo_2009/tilstand_okosyst_BH2sammendrag.pdf/en

September 23, 2009

Summary

The commercial fish stocks in the Barents Sea are, with a few exceptions, in a healthy condition. Positive trends are a growing capelin stock and an increasing spawning stock of Northeast Arctic cod. In a long-term perspective, the water masses are warm, although on average, not as warm as in 2006 (Figure B1). The stock level of blue whiting, a more southern species, has decreased in 2008.

Figure B1. Temperature anomaly in the core of the Atlantic Water flowing into the Barents Sea between Norway and Bear Island (the Fugløya-Bear Island transect). The series are deviations from the long-term mean temperature between 50 and 200 m. Observed values (blue line) and 1 year moving average (red line) are shown. The straight line represents a linear trend over the period.

A clean ocean

Although wind and ocean currents transport various contaminants into the Barents Sea, the level observed in organisms is generally low. The main exception is top predators such as the polar bear, where persistent organic contaminants aggregate.

High temperatures

The water masses in the Barents Sea have been extraordinarily warm since 2000 (Figure B1). However, 2008 was slightly cooler than 2007. This is probably due to a strong reduction of the transport of Atlantic water into the Barents Sea. The amount of ice in the Barents Sea in 2008 was low (Figure B2).

Figure B2. Ice area anomaly for the sector 25–45°E in the Barents Sea, which is the area with the highest variability in ice cover. Monthly mean (blue line) and 1 year moving average (red line) are shown relative to the mean ice area for the period 1987–2007. The straight line represents a linear trend over the period.

Decreasing levels of zooplankton

Compared with the two previous years, considerably less zooplankton was observed in the Barents Sea in 2008. This may be due to a lesser amount of Atlantic water being transported into area, but an increasing capelin stock grazing on zooplankton, mainly copepods and krill, may have contributed to the decrease.

Capelin up, blue whiting down

Based on the number of immature capelin, the stock prognoses indicate an increasing capelin stock the coming year. This is contrary to the prognoses for the other important plankton feeder in the Barents Sea, the young and immature stock (ages 1-4) of Norwegian spring-spawning herring. The year classes 2005-2008 of this stock are smaller than previous years. A decreasing amount of blue whiting is recorded. For polar cod the stock situation seems unchanged.

Healthy stock of Northeast Arctic haddock

The size of the spawning stock of Northeast Arctic cod is slowly increasing and is above the historical average. As in 2007, ICES emphasizes that it is of great importance for the development of this stock that the IUU (illegal, unregulated, unreported) fishery the Barents Sea is stopped. The exact stock size for the Northeast Arctic haddock is difficult to determine. However, the spawning stock is at a relatively high level and strong immature year classes, which will recruit to the spawning stock in the coming years, are observed. The third major demersal fish stock in the Barents Sea, the Greenland halibut, is slowly recovering from a period below historic levels.

References:

Figures from http://www.imr.no/filarkiv/havets_ressurser_og_miljo_2009/1.2_Abiotiske_faktorer_fysikk_sirkulasjon.pdf/en.

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