Capelin stock in the Barents Sea (Mallotus villosus)

Capelin on white background.
Photo: Institute of Marine Research

Capelin are an important food source for fish, seabirds and marine mammals and are accordingly considered to be a key species in the Barents Sea.

What is being monitored?

The capelin stock in the Barents Sea

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The capelin stock is characterized by major fluctuations. Since systematic monitoring began in the early 1970s, the stock has collapsed 4 times, initially in the mid-1980s and then in 1993–1997, 2003–2006 and then now. In the three first periods, large year classes of young herring entered the Barents Sea, and the main reason for the collapses in the capelin stock seems to have been that the young herring fed on capelin larvae. The present collapse is probably due to a large stock of cod feeding on the capelin larvae.

Status and trend

The capelin stock was measured at 0.41 million tonnes in September 2019, of which the mature stock comprised 0.30  million tonnes. This mature stock is estimated to amount to around 0.08 million tonnes at spawning time in the spring of 2020. This stock level does not justify opening the capelin fishery in 2020.

Causal factors

The capelin stock undergoes large fluctuations, even in the absence of human impact such as fishing. This may be explained by capelin being short-lived (typically 3-4 years) and normally subject to strong predation by other fish, sea birds and sea mammals. This applies to both capelin fry and adult fish.

In 2015, the stock was considered collapsed for the fourth time since 1983. In 2017, measurements showed that the stock was once again large enough to allow for fishing. During the 2018 winter, 195 000 tonnes were caught. The results from 2018 showed a slight stock decline, while the results from 2019 indicated a stock below the 2015 level. The reqruitment has been low the last six years and the Joint Norwegian-Russian Fisheries Commission made a recommendation of a null quota in 2020.

Consequences

Fluctuations and collapses in the capelin stock have previously caused domino effects in the Barents Sea ecosystem.

Collapses of the capelin stock in the 1980s had major consequences for predators that feed on capelin, such as cod and harp seals. It was observed that cod had reduced growth, delayed maturation and individuals were leaner. Cod changed their diet and started to eat less nutritious foods such as crustaceans, and cannibalism became more widespread in that cod ate codlings. Food shortage caused Harp seals to embark on large feeding migrations both southwards and westwards, which among other things led to 77,000 harp seals drowning in nets along the Norwegian coast in 1987–1988. Collapses in the capelin stock in recent times have not had the same ecosystem consequences, possibly because predators have had access to better alternative food sources.

About the monitoring

The indicator is based on international advice from ICES.

The stock assessment and development are based on the annual Norwegian-Russian research cruise in the Barents Sea in September. The measurements are acoustic data which are used in a model in which maturation, growth and mortality (including grazing pressure from cod) are calculated, based on gut samples. An assessment of uncertainty in the cruise estimate and other input data is included. The quantitative assessment indicates an absolute stock level, calculated by the CapTool model, which obtains its parameters from the Bifrost model. In addition, FangstFisk is used to produce catch data for Bifrost and BEAM, which calculates volumes. The fishing industry pays particularly close attention to the prognosis, which is simulated in CapTool for 6 months.

Places and areas

Relations to other monitoring

Monitoring programme
International environmental agreements
Voluntary international cooperation
Related monitoring