Illustration: Jón Baldur Hlíðberg
Icelandic summer spawning (top) and Atlanto-Scandian (bottom) herring fishing grounds in 20010/2011 fishing season (t/nm2), all gear combined, dark areas indicate highest catches
Source: The Marine Research Institute
Total catch (t) of herring in Icelandic waters and Icelandic catch of herring in other waters
Total catch (t) of Icelandic summer and Icelandic spring spawning herring (only fished in Icelandic waters)
Source: The Marine Research Institute
Total catch (t) of the Atlanto-Scandian herring in the Northern Atlantic Ocean
Herring catch (t) by month
Source: Statistics Iceland, weight treports
Icelandic summer spawning (top) and Atlanto-Scandian (bottom) herring catch (t) by fishing gear
Source: Statistics Iceland, weight reports
Icelandic summer spawning (top) and Atlanto-Scandian (bottom) herring spawning stock biomass and average fishing mortality
Source: The Marine Research Institute
Icelandic summer spawning herring catch (t) by type of processing
Source: Statistics Iceland, processing reports
Value of exported herring (all stocks) products by main countries in 2008 (FOB million ISK)
Source: Statistics Iceland
Scientific: Clupea harengus. English: herring. Icelandic: Síld. For more languages see the Marine Animal Dictionary.
Biology and distribution
The herring is the most abundant fish in the North Atlantic, a close relative, the Pacific herring (Clupea pallasi) is also found in the northern Pacific Ocean. It is a pelagic zooplankton feeder, mostly feeding on the copepods Calanus finmarchicus. It is commonly between 30 and 40 cm length; the largest herring measured in Icelandic waters was 46.5 cm. It is a multispawner as opposed to the capelin and generally spawns in shallow waters in spring or summer. It can reach up to 25 years of age.
The North Atlantic herring is split into many stocks, based on where and when they spawn. Historically, the largest of these stocks is the Atlanto-Scandian herring (also called the Norwegian spring spawning herring). This stock spawns along the coast of central Norway. Generally the larvae then drift to nursing areas along the coast of northern Norway, Russia and in the Barents Sea, where the juveniles stay until they are sexually mature at the age of 4 to 6. When mature, the herring undertook large scale feeding migrations to the waters north and east of Iceland. During winter the stock condensed into large schools in the waters east of Iceland and during the spring it went back to the Norwegian spawning grounds. This pattern does however change with oceanographic conditions, stock size and stock composition.
The Icelandic summer spawning herring is different from the Atlanto-Scandian stock as this stock is a coastal stock and does not leave Icelandic waters. It also differs in another respect, as it spawns in July. Currently these two stocks have quite separate distribution patterns and do not mix in Icelandic grounds, although previously they shared similar feeding grounds in early summer, north or east of Iceland.
The third stock in Icelandic waters was the Icelandic spring spawning herring. The life cycle of this stock was quite similar as for the Atlanto-Scandian stock except that it did not migrate to Norwegian waters to spawn but spawned in Icelandic waters. This stock collapsed at the same time as the other stocks, and has not recovered.
Catch and fishing gear
The herring stocks in the Northeast Atlantic have sustained small scale coastal fisheries for centuries (see "Herring bonanze and failure"). Herring catches by Icelanders were less than 30 thousand tonnes until after W.W.I when they increased to around 200 thousand tonnes. These catches were mostly confined to local Icelandic stocks. After the war, catches declined again but increased rapidly again after 1960 to more than 600 thousand tonnes just before the collapse. Most of these catches came out of the Atlanti-Scandian stock.
In the mid 20th century large offshore fisheries for herring were developing with better technology. Catches of the largest stock, the Atlanto-Scandian herring increased rapidly after 1950 and reached a peak of nearly 2 million tonnes in 1966, but then collapsed almost entirely in 1969. Most other herring stocks in the North Atlantic were decimated at a similar time. The increase in catches can be explained by rapidly advancing technology, such as the power block which enabled the boats to haul larger catches and the sonar which allowed them to spot the schools in deep waters. Oceanographic conditions also worsened at this time. Considerable catches of 200 to 500 thousand tonnes annually of juvenile herring in Norwegian waters were probably also one of the main reasons for the collapse. This collapse was a big setback for the economies depending on these fisheries. The Icelanders were especially hard hit because of the great importance of the herring fisheries for their economy.
After the collapse, a near moratorium was soon established on the herring fisheries. Until 1984 catches of the Atlanto-Scandian stock were always less than 20 thousand tonnes annually. From 1986 to 1992 catches were around 100 thousand tonnes annually. After this time, strong year classes have been recruited to the fishery and the stock has been rebuilding fast. Catches did increase to a maximum of 1.5million tonnes in 1997. Total catches have been in the range of 750 thousand to 1,3 million tonnes since then. Because of the increased stock size, the Atlanto-Scandian herring stock now again undertakes large migration movements to the Norwegian Sea and into Icelandic waters, considerable catches are now taking place in Icelandic waters.
Icelanders began catching this herring again in 1994 and the annual catches since then have been between 100 and 200 thousand tonnes, still mostly outside the EEZ.
The current fishery for the Atlanto-Scandian stock is controlled by the setting of a TAC, which is then divided between nations involved according to annual agreements. The countries can take a certain percentage of their catch in each other’s EEZ according to bilateral agreements. Each country decides how its quota is split between vessels and when the fishery is conducted. The division of the TAC between countries has been based on distribution of the stock, historical catches, contribution to scientific research and the nation’s dependency on fisheries. The aim of the management is to keep the fishing mortality rate at or below 0.125
Most of the herring catches in Icelandic waters since the collapse in 1967 have been taken out of the Icelandic summer spawning herring. Historically, this stock has always been much smaller than the Atlanto-Scandian stock and does not undertake migrations outside the Icelandic EEZ. This stock also collapsed in 1967, but was faster to recover than the Atlanto-Scandian stock. The size of the Icelandic stock is now close to record high levels, and it sustained catches of around 100 thousand tonnes or more annually. However, the stock has recently been hard hit by Ichthyophonus infections.
See the Marine Research institute
Processing and markets
The herring is both reduced into meal and oil, and frozen or salted for human consumption. When herring fisheries started around Iceland in the late 19th century, most of the catch was salted to preserve it for human consumption. The herring was a valuable fish and salted herring fetched high, although variable prices on international markets, especially in northern, north-western and north-eastern Europe. As catches increased, more of the catch was processed into fishmeal and oil.
The fish meal is sold all over the world and is used as feed for domestic animals, such as chicken, pigs and many other types of livestock. Fish meal is also used as feed for other fish species in aquaculture, hence a large part is expored as salmon feed to Norway. Fish oil is used for a variety of food and industrial products, such as margarine and paint. The catch that is not reduced is mostly frozen at sea or after landing, exported to eastern Europe and then processed further.
References and further information
Jakobsson, J. and Stefánsson, G. (1999). Management of summer-spawning herring off Iceland. ICES Journal of Marine Science, 56: 827-833.
Jakobsson, J., Vilhjálmsson, H. and Schopka, S.A. (1969). On the biology of the Icelandic herring stocks. Rit Fiskideildar, 4(6): 1-16.
Jakobsson, J. and Östvedt, O.J. (1999). A review of joint investigations on the distribution of herring in the Norwegian and Iceland Seas 1950-1970. Rit Fiskideildar, 16:209-238.
Jónsson, G., & Pálsson, J. (2006). Íslenskir fiskar (Icelandic fishes). Reykjavík, Iceland. 336 p (in Icelandic)
Gíslason, Á. and Ástþórsson, Ó.S. (2002). The food of the Norwegian spring-spawning herring in the western Norwegian Sea in relation to the annual cycle of zooplankton. Sarsia, 87: 236-247.
Óskarsson, G.J., Guðmundsdóttir, Á and Sigurðsson, Þ. (2009). Variation in spatial distribution and migration of Icelandic summer-spawning herring. ICES Journal of Marine Science 66: 1762-1767.
Óskarsson, G.J. and Pálsson, J. (2011) The Ichthyophonus hoferi outbreak in the Icelandic summer-spawning herring stock during the autumns 2008 to 2010. ICES Benchmark Workshop on Roundfish and Pelagic Stocks, WKBENCH, 24-31 January 2011, Lisbon, Portugal. Working document Her-Vasu No. 2. 1-17 pp
Óskarsson, G.J. and Taggart, C.T. (2009). Spawning time variation in Icelandic summer-spawning herring (Clupea harengus L.). Canadian Journal of of Fisheries and Aquatic Science 66: 1666-1681
Óskarsson, G.J. and Taggart, C.T.(2010). Variation in reproductive potential and influence on Icelandic herring recruitment. Fisheries Oceanography. 19: 412-426.
Toresen, R. and Jakobsson, J.(2002). Exploitation and management of Norwegian spring-spawning herring in the 20th century. ICES Marine Science Symposia, 215:558-571.
Hreiðar Þór Valtýsson, University of Akureyri