Atlantic Herring

Herrings feed mainly on small oceanic shrimps or copepods and can filter-feed if there are sufficient densities of its prey to allow this. Individuals reach maturity between the ages of three and nine years. At any month of the year, one of the many populations scattered across its vast range will be spawning. The eggs are sticky and are laid on marine vegetation or the seabed. Fish in the North Sea spawn between January and April at a depth of no more than 70 metres and a sea temperature of 4 - 7 °C.

The Atlantic herring is listed in the UK Biodiversity Grouped Action Plan for commercial marine fish. Being a species that is found in international waters, it has proved very difficult to impose restrictions on the number of fish that can be harvested from the sea without reducing fish stocks below the important Safe Biological Figure (SBF) limits. During the 1960s, the herring population in parts of the north Atlantic collapsed catastrophically, virtually wiping out the Icelandic herring industry, and posting a warning sign about the fragility of the marine environment. The chief cause was overfishing and, following the creation of a management plan in 1975, the Icelandic herring industry became the first to be subject to a total allowable catch (TAC) restriction. Since then, in this part of the Atlantic, herring fish stocks have recovered to sustainable levels, and the experience should serve as a lesson as to what could happen to other commercially important species. Whilst Atlantic populations of herring are currently considered to be above the SBF, those in the North Sea are giving cause for concern. Figures suggest that reproduction of many commercial fish species fell to an all-time low in the 1990s. Although populations now seem to be recovering, the herring is still covered in the part of the UK Grouped Action Plan specifically relating to North Sea fish stocks. However, it remains to be seen whether implementing the rules and recommendations in the current Common Fisheries Policy (CFP) will allow population levels to stabilise and recover. One effect of the CFP has been to remove the inefficient fishing boats from the fleets, allowing heavy overfishing by the 'factory' trawlers. This, coupled with the pressure on individual governments to support their country's own fishing fleets, has led to the harvesting of 'black fish', illegal catches above and beyond a country's legal quota, and this is still taking its toll on herring populations.

Many people will be familiar with the herring as, for many years, it has been a staple of the fishmonger's slab. It is a shoaling fish and has the classical fish shape, and is silvery and streamlined. It has a single dorsal fin, and pelvic fins positioned slightly in front of the line of the dorsal fin. The pectoral fins, like the others on the fish, are soft and not stiff and 'bony' like on many other fishes. The lower jaw protrudes forward of the upper lip, and there is no visible lateral line. The body is deeper than it is wide, improving the streamlining, and the tail is deeply forked. The colouring of the body overall is silver, but closer inspection reveals that there is a darker blue iridescence over the upper half of the body, whilst the underside is paler. This colouration is called 'countershading', and provides a way of camouflaging the fish from attacks by its many predators from all angles.

This species is 'pelagic' in its distribution throughout the ocean, in the surface waters down to a depth of about 200 metres. These fish stay away from the immediate coastal areas outside the spawning season. Herring avoid the deeper parts of the ocean, and are often found in vast surface shoals, covering several square kilometres of water.

The Atlantic herring is found over much of the northern part of the Atlantic Ocean, from the Bay of Biscay northward to Iceland and southern Greenland. It extends north-eastward to Spitzbergen and Novaya Zemlya in the Arctic Ocean, as well as into the Baltic. To the west, it ranges along the east coast of North America, from south-western Greenland and Labrador, down to South Carolina. Around UK waters, the herring occurs in the English Channel, the Irish Sea and the North Sea. There are a number of different races of the fish, found across its eastern range, in the Baltic and North Sea, and in Norwegian and Icelandic waters. The various races spawn at different times of the year.

Not subject to specific protection, but listed by the International Council for the Exploration of the Seas (ICES) as below Safe Biological Limits (SBL).

The biggest threat to this species is over-harvesting by the fishing fleets of many nations. Although the herring is still a relatively numerous species, it is now feared that there more are being caught by trawlers than can reproduce annually, particularly in European waters. Domestic pressure on governments to support their fishing industries has led to overfishing, and agreed quotas being exceeded, depleting populations of herring across much of its range.