Capelin stock in the Barents Sea (Mallotus villosus)
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?
Cite these dataInstitute of Marine Research (2021). Capelin stock in the Barents Sea. Environmental monitoring of Svalbard and Jan Mayen (MOSJ). URL: http://www.mosj.no/en/fauna/marine/capelin.html
|Recruits||109||Institute of Marine Research||529||305||190||211||360||84||12||270||403||528||515||155||39||6||38||21||189||700||402||351||2||20||7||82||99||179||156||449||114||60||82||51||27||60||222||313||124||248||209||146||324||105||40||32||86||59||17|
|Mature stock||109 kg||Institute of Marine Research||1.35||0.91||2.92||3.2||2.68||1.4||1.23||3.91||1.55||1.59||1.33||1.21||0.29||0.07||0.02||0.2||0.18||2.62||2.25||2.23||0.33||0.09||0.12||0.25||0.31||0.93||1.72||2.1||2.02||1.29||0.28||0.29||0.17||0.44||0.84||2.47||2.32||2.05||2.12||2||1.47||0.87||0.38||0.18||1.72||1.06||0.31|
|Immature stock||109 kg||Institute of Marine Research||3.79||4.83||4.89||3.22||2.21||2.85||2.94||2.8||2.34||2.19||2.9||1.76||0.58||0.06||0.08||0.23||0.69||3.21||5.04||2.92||0.47||0.11||0.08||0.26||0.6||1.12||1.06||2.18||1.61||0.92||0.25||0.33||0.15||0.35||1.28||1.96||1.44||1.45||1.59||1.59||2.49||1.08||0.47||0.15||0.78||0.54||0.11|
The assessment of capelin stock size and development is based on data from the yearly Norwegian-Russian research cruise in the Barents Sea in September. The stock size is estimated on the basis of acoustic data, supported by pelagic trawl data using the StoX software. The quantitative assessments from the cruise are assumed to reflect absolute stock levels. The stock measurements are then input into a stock prognosis model, CapTool, which obtains its parameters for maturation, growth and mortality (including grazing pressure from cod) from the Bifrost model. An assessment of uncertainty in the cruise estimate and other input data is included in the prognosis.
Uncertainties related to the indicator depends on the accuracy and precision in the capelin stock assessment from the joint Norwegian- Russian cruise in September.
Reference level and action level
The reference level: None
The Norwegian-Russian Fisheries Commission has decided a management rule that states that there should be less than 5 percent probability that the spawning stock should be less than 200,000 tons at the time of spawning. ICES advices on capelin management based on this rule.
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.
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.
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