Biomass of polar cod in the Barents Sea
Last updated 4 June 2026
The polar cod (Boreogadus saida) is the only strictly arctic pelagic fish species in the Barents Sea. It is adapted to Arctic water masses, with temperatures down to the freezing point. The cold water defines its available habitat. The amount of polar cod may give an indication of the conditions for an Arctic fish population in the Barents Sea.
What is being monitored?
Biomass of polar cod
The figure shows the development of polar cod biomass in the Barents Sea, measured with acoustics during autumn from 1986 to 2025. There are large fluctuations in the biomass throughout the monitoring period. The fluctuations are likely due to a combination of change in population size and change in distribution. The polar cod population has a distribution reaching further north and east than the area covered by the annual monitoring survey in the Barents Sea.
(Cite these data: Institute of Marine Research (2026). Biomass of polar cod in the Barents Sea. Environmental monitoring of Svalbard and Jan Mayen (MOSJ). URL: https://mosj.no/en/fauna/marine/polar-cod.html)
Details on these data
| Last updated | 4 June 2026 |
| Update interval | Yearly |
| Next update | May 2027 |
| Commissioning organization | Ministry of Trade, Industry and Fishery |
| Executive organization | Institute of Marine Research |
| Contact persons | Georg Skaret |
Method
The biomass of polar cod is monitored using acoustics and trawling during the annual Norwegian-Russian Ecosystem Survey in the Barents Sea.
The survey follows transects which are evenly distributed over the Barents Sea, but the northernmost parts of the polar cod distribution area are not covered.
Standard methodology for biomass estimation with acoustic trawling surveys is used. Acoustic echo sounder recordings along the transects are first allocated to different target species based on their “acoustic signatures” (i.e. echo strength, response to different frequencies), and the composition of trawl catches. The integrated acoustic values are then converted to biomass. The conversion is based on how much echo an average fish of a certain length gives.
There are several sources of uncertainty with this method, both connected to the actual measurement, detection, interpretation, converting from acoustics to biomass and the degree of coverage. A summary of such uncertainty for equivalent surveying of herring in Norwegian waters is found in Løland et al., 2007.
A fundamental prerequisite for attaining a total estimate for the stock is that the entire distribution area is covered. This is not the case for polar cod in the Barents Sea, and hence the estimate is valid only for the portion of the stock present in the surveyed part of the Barents Sea during autumn.
Quality
Echosounders are calibrated before every cruise, using standard methods described in Foote et al.,1987.
Sampling in laboratory uses methods described in Mjanger et al., 2007.
Other metadata
Data from the joint Russian/Norwegian ecosystem survey in the Barents Sea are available in the Institute of Marine Research’s database. Other metadata are found in the annual reports from the ecosystem survey of the Barents Sea (BESS).
Reference level and action level
There is no reference level or action limit.
Status and trend
The amount of polar cod in the Barents Sea has been low, at ca. 10% of the long-term average both in 2024 and 2025. In most years since 2012, the polar cod biomass has been below the long-term average. However, during this period the biomass has twice increased to record high levels after which it has rapidly declined again. The estimated abundance at age in 2025 was below the long-term average for all age groups.
Causal factors
It is expected that the abundance of polar cod in the Barents Sea will decrease as a consequence of reduced ice cover and a warming ocean reducing the extent of adequate habitat (Kjesbu et al. 2022). The distribution of polar cod has changed in later years, and the traditional spawning areas in the south-east Barents Sea are now only used to a very low degree. The spawning now almost exclusively happens around Svalbard (Eriksen et al. 2015; Huserbråten et al. 2019), and this change will influence survival. Despite the generally low biomass level of polar cod since 2012, there have been two occasions with biomass increasing drastically and decreasing again rapidly during this period. The causes for this are not known.
Consequences
The Polar cod stock in the Barents Sea is a potential prey for cod, sea birds and seals. During periods with large stocks of important predators, like the cod, polar cod may be important prey.
About the monitoring
Polar cod is monitored yearly as a part of the ecosystem survey in the Barents Sea in the autumn.
Places and areas
The Barents Sea
Relations to other monitoring
Monitoring programme
- None
International environmental agreements
- None
Voluntary international cooperation
- None
Related monitoring
- None
Further reading
Links
Publications
- Eriksen, E., Ingvaldsen, R. B., Nedreaas, K., & Prozorkevich, D. (2015). The effect of recent warming on polar cod and beaked redfish juveniles in the Barents Sea. Regional Studies in Marine Science, 2, 105-112. https://doi.org/10.1016/j.rsma.2015.09.001.
- Foote, K. G., Vestnes, H. P., MacLennan, D. N., & Simmonds, E. J. (1987). Calibration of acoustic instruments for fish density estimation: a practical guide. ICES Cooperative Research Report, 144: 69 s. https://doi.org/10.17895/ices.pub.8265.
- Huserbråten, M. B. O., Eriksen, E., Gjøsæter, H., & Vikebø, F. (2019). Polar cod in jeopardy under the retreating Arctic sea ice. Communications Biology, 2(1), 407. https://doi.org/10.1038/s42003-019-0649-2.
- Kjesbu, O. S., Sundby, S., Sandø, A. B., Alix, M., Hjøllo, S. S., Tiedemann, M., … & Huse, G. (2022). Highly mixed impacts of near‐future climate change on stock productivity proxies in the North East Atlantic. Fish and Fisheries, 23(3), 601-615. https://doi.org/10.1111/faf.12635
- Løland, A., Aldrin, M., Ona, E., Hjellvik, V., & Holst, J. C. (2007). Estimating and decomposing total uncertainty for survey-based abundance estimates of Norwegian spring-spawning herring. ICES Journal of Marine Science, 64(7), 1302-1312. https://doi.org/10.1093/icesjms/fsm116.
- Mjanger, H., Hestenes, K., Olsen, E. M., Svendsen, B. V., Wenneck, T. d., & Aanes, S. (2007). Håndbok for prøvetaking av fisk og krepsdyr. Bergen. Institute of Marine Research, 3.
- Simmonds, E.J., & MacLennan, D. N. (2005). Fisheries acoustics: Theory and Practice. Blackwell Publishing Ltd, Oxford. 437 s. https://doi.org/10.1002/9780470995303.