Stock of young herring in the Barents Sea

Last updated 25 October 2022

The herring (Clupea harengus) stock in the Barents Sea is now at a low level, after a temporary rise due to a strong year class in 2016.

Status and trend

The data for young herring are presented as a biomass index. It is an index that is calculated based on research cruices that measure the amount of fish using sonar recordings combined with trawl samples of the fish.

In 2017, a lot of 1-year olds were observed, and the biomass index for the 2016-year class was the highest since the year class of 2004 was measured as 1-year olds in 2005. High biomass index for the 2016 year class was further confirmed in 2019,- now as a relatively high estimate of 3-year olds. Due to lack of coverage, no herring index was calculated for 2018.

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 significantly affecting the ecosystems. Herring is therefore also a key ecosystem player, even if it only stays in the Barents Sea when young and migrate before maturation.

The amount of young herring can also affect cod. Cod eat herring, but stomach samples shows that herring only partially replaces capelin as food for cod. When large quantities of juvenile herring are present in the Barents Sea, growth of the cod stock in the Barents Sea will therefore be reduced.

Causal factors

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.

Consequences

Recruitment to the herring stock will vary greatly from year to year. It is now little young herring in the Barents Sea after the numerous 2016-year class has largely left the Barents Sea.

About the monitoring

The indicator describes the amount of herring that are 1-3 years old, and how this change 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.

Further reading