There are several stocks of herring in our waters, of which the Norwegian spring-spawning herring is the largest. Herring swim in huge schools, going as deep as 200 metres. The Norwegian Spring Spawning herring winter off the coast of Northern Norway, then spread out along a large part of the Norwegian coast to spawn in early spring. After spawning, the herring make feeding migrations into large parts of the Norwegian Sea, before returning to the wintering area. The larvae follow the current north to the Barents Sea, where the young herring grow to maturity. Herring can reach a length of 40 centimetres and weigh more than 500 grams. Its life span is up to 25 years.
The fishing season for Norwegian spring-spawning herring is mainly from October to March. Herring are sold as fresh and frozen fillets and as whole fish. Many types of processed herring are available, e.g. salted, hot or cold smoked and various types of marinated herring.
Herring are a very good source of vitamin D. They are also rich in marine omega-3, but fat contents vary seasonally.
Contents of undesirable substances
Norwegian spring-spawning herring are safe to eat. The concentrations of heavy metals and persistent organic pollutants (POPs) in this type of herring are low. The levels of POPs are somewhat higher in January-February, just before spawning, than during the rest of the year.
During 2006-2008, NIFES sampled and analysed 800 Norwegian spring-spawning herring from 29 positions for a thorough survey of undesirable substances, known as a baseline study.
Norwegian spring-spawning herring is currently monitored every third year in January-February. Twenty-five fish are then sampled from each of two positions in the spawning grounds.