Biomass of polar cod in the Barents Sea (Boreogadus saida)

A polar cod in natural surroundings.
Photo: Bjørn Gulliksen / University of Tromsø

The polar cod is the only strictly pelagic fish species in the Barents Sea. It is adapted to Arctic water masses, with temperatures down to freezing point. The cold water defines its available habitat. The amount of polar cod may give an indication of the conditions for an Arctic population in the Barents Sea.

What is being monitored?

Biomass of polar cod

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The figure shows the development of polar cod biomass in the Barents Sea, measured with acoustics during autumn from 1986 to 2017. There are large fluctuations in the biomass throughout the monitoring period. The most obvious explanation for the fluctuations is 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 where the measurements are performed in the Barents Sea.

Status and trend

In 2016, the biomass of polar cod increased sharply after a long period of declining. Monitoring data suggested that 1-year-olds totally dominated the biomass. However, the amount of 2-year-olds registrered in 2017 was much lower than what was expected based on the survey in 2016, and the total biomass was greatly reduced from 2016 to 2017. There were low registrations of polar cod also during the voyage in the autumn of 2018, but the area coverage in the east was considered too poor to assess the state of the stock.

Causal factors

The sharp increase in the biomass of polar cod from 2015 to 2016 came as a surprise, with no preceding indication of such a development and a long period of decline leading up to it. When the population level declines from 2016 to 2017, it may be caused by changes in the distribution pattern that has led part of the cod popoulation out of the survey coverage.

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, this may be important.

About the monitoring

Polar cod is monitored yearly as a part of the ecosystem cruise in the Barents Sea in the autumn.

Places and areas

The Barents Sea

Relations to other monitoring

Monitoring programme
International environmental agreements
Voluntary international cooperation
Related monitoring