Stock of young herring in the Barents Sea (Clupea harengus)
In recent years, the herring stocks has declined, but now seems to have stabilized. To prevent further decline, we depend on good fish management and use of the precautionary principle.
What is being monitored?
Cite these dataInstitute of Marine Research (2019). Biomass index for young herring 1–3 years in the Barents Sea. Environmental monitoring of Svalbard and Jan Mayen (MOSJ). URL: http://www.mosj.no/en/fauna/marine/young-herring-population.html
|1 year||index||Institute of Marine Research||406||984||34||148||1||48.4||34.5||3||36.2||202.2||40.2||5.7||130.5||820|
|2 years||index||Institute of Marine Research||2725||1055||398||218||77||51.8||33.7||105.5||65.5||321.6||28.5||529.8||126.2||141|
|3 years||index||Institute of Marine Research||107||795||211||810||287||287||37||0.8||194.8||12.5||449.5||285.4||389.5||412|
The estimation of the stock of young herring (1–3 years old) is carried out in autumn each year during the joint Norwegian-Russian ecosystem cruise in the Barents Sea. The estimate is based on acoustic data where the integrated echo sound quantity is combined with biological data from trawl hauls to estimate the number and biomass in specific age groups.
The greatest uncertainty in the estimate will be attached to obtaining representative samples in the trawl haul. This may lead to over- or underestimating the number and biomass in specific age groups.
Fish stock assessment data are available at the International Council for the Exploration of the Sea (ICES).
Reference level and action level
Young herring are not harvested, but the reference level for adult Norwegian spring-spawning herring is the precautionary limit for the spawning stock. The action limit is when the estimated spawning stock is below the precautionary limit for the spawning stock.
Status and trend
The last large year class of young herring in the Barents Sea was in 2004, and the last years, there has been little young herring left in the Barents Sea. In 2018, a lot of 1-year olds were observed, and the biomass index was the highest since the year class of 2004 was measured as 1-year olds in 2005.
The quantity of young herring is mainly connected with factors like the population size of the spawning stock, and physiological as ecological conditions in the Norwegian Sea. Conditions in the Barents Sea will significantly influence the growth and mortality of the individual year class.
A large quantity of young herring in the Barents Sea is an important ecological factor. The herring in the Barents Sea prey on capelin larvae, and the growth of the capelin stock is poorer when there is a strong stock of young herring in the Barents Sea.
Capelin is considered a keystone species affecting ecosystems significantly. Herring is therefore also a key player in the ecosystem, even if it only stays in the Barents Sea when young and emigrant before maturation.
The amount young herring can also affect cod. Cod eat herring, but stomach samples shows that the herring only partially replaces capelin as food for cod. When large quantities of juvenile herring is present in the Barents Sea, increase in cod stock in the Barents Sea will therefore be reduced.
In recent years there has been little juvenile herring in the Barents Sea. In 2013 there were observed relatively much zero-old herring in the Barents Sea. This year class is for the most part out of the Barents Sea. In 2017, a lot of 1-year olds were observed in the Barents Sea, and the year class of 2016 seems to be the most numerous since the year class of 2004.
Young herring in the Barents Sea are affected by many factors such as the sea temperature, the availability of food and the occurrence of capelin and cod.
The herring fishery mainly takes place outside of the Barents Sea. The young herring in the Barents Sea are protected by international agreements and are harvested to a very limited extent.
The Norwegian spring-spawning herring stock suffered a collapse around 1970 due to heavy overfishing. In 1972, the spawning stock was so low that only two herring larvae were found during the annual larvae estimation cruise along the entire Norwegian coast.
Recruitment to the herring stock will vary greatly from year to year. In recent years there has been little young herring in the Barents Sea. It seems like the 2013 year class, of which it was measured relatively many of as zero-olds, is mostly out of the Barents Sea. However, it looks like the 2016-year class is numerous, and may affect the ecosystem in the Barents Sea the following years.
About the monitoring
The indicator describes the amount of herring that are 1-3 years old, and how this changes over time. The amount of herring from this age group is considered as a good starting point for assessing the amount of immature herring in the Barents Sea.
The time series going back to 1973. The Institure of Marine Reseach (www.imr.no) is responsible for monitoring the herring stock.
Places and areas
Relations to other monitoring
- Monitoring programme
- International environmental agreements
- Voluntary international cooperation
- Related monitoring