Atlantic cod (Gadus morhua)
|Size||Length: up to 150cm|
|Weight||up to 40kg|
The Atlantic cod is classified as Vulnerable (VU) on the IUCN Red List (1). 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 Atlantic cod (Gadus morhua) is probably the best-known fish caught commercially in UK waters. In appearance, the head is rather disproportionately large for the body, with the upper jaw protruding over the lower. The colour of the body can vary depending on the habitat in which the fish is found, but ranges from reddish or greenish where the water is populated by algae, and pale grey where the fish is found in deep water or near a sandy bottom. The cod has a barbel on the end of its chin and, in common with several other members of the family, three dorsal and two anal fins. The tail fluke is square-ended, and the lateral line is noticeable and extends from the point of the gill covers to the centre of the tail root.
Atlantic cod range from the north and eastern coast of North America, around the southern tip of Greenland across the north Atlantic to the waters around Iceland, the Faroes, the North Sea and the Barents Sea. It is found all around the British coast, reaching south to the Bay of Biscay.
Atlantic cod can be found in coastal waters with depths of 500 to 600 metres, and in the open ocean.
Like the herring, there are various races of cod, which differ in their growth rates, distribution and times of spawning. Most cod spawn between the months of January and April and a female, if she is large enough, can release up to five million eggs. Depending on the temperature, the eggs hatch in two to four weeks and the young cod drift in the open ocean, feeding on small crustaceans. Atlantic cod will eat a wide variety of prey, ranging from other fish (up to the size of herring) to worms; they also take swimming crabs, shrimps and prawns.
The different races of this fish vary in the ages and weights attained before they become sexually mature. The migratory cod found off the coasts of Newfoundland, Iceland and Norway mature at around 8 to 12 years old when they may weigh up to eight kilogrammes. Coastal cod mature more rapidly and may be able to reproduce at the age of three years.
The Atlantic cod is a fish in crisis. The fish stocks in the Irish Sea have fallen drastically within the last few years. Recent figures compiled and published by the European Environment Agency (EEA) warn that the risk of a collapse of the fish stock in the North Sea is high, and that populations are now outside safe biological limits. The spawning stock biomass (the breeding population of the fish) hit an historic low figure during 2001, and during February and April that year, much of the North Sea was closed to fishing fleets as part of an emergency plan to protect young cod.
It is also thought that the spawning stock biomass for the North Sea has been below the ‘biomass precautionary approach reference point’ - the critical level for sustaining the population - for almost two decades, and this warning also applies to waters adjacent to the North Sea. Throughout its range, the harvesting of young fish before they have been able to reproduce successfully is a serious threat to Atlantic cod.
The Atlantic cod 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. The International Council for the Exploration of the Sea (ICES) released figures for the North East Atlantic and Baltic in 2001, which show cod are still being overfished within six of the nine sea areas of the study. Currently, cod caught in Icelandic waters are the only stock regarded as being sustainably fished.
In January of 2003, the European Union (EU) revised its Common Fisheries Policy (CFP), but whether this will lead to improvements in the way the fishing industry is regulated remains to be seen. Although the fish that are landed in port are controlled through the rules governing total allowable catch (TAC), the regulations do not limit the numbers of fish actually caught. A boat’s crew, having checked the catch and finding either bycatch (non-target fish or other animals) or fish below the legal size, will simply jettison those fish overboard. Most of them will be dead.
Many marine biologists argue that regulation alone will not be enough to maintain fish stocks at a sustainable level. The present status of the Atlantic cod stock seems to support this statement. Perhaps the only hope for the future of this fish, and the other commercial species, is the imposition of no-catch zones, including some of the principal migration routes, and areas where fish can spawn undisturbed.
Find out more on the Atlantic cod and other fish species:
Information supplied by English Nature.
- Algae: simple plants that lack roots, stems and leaves but contain the green pigment chlorophyll. Most occur in marine and freshwater habitats.
- Anal fin: in fish, an unpaired fin on the under surface of a fish, behind the anus.
- Barbel: fleshy projection near the mouth of some fish.
- Crustaceans: diverse group of arthropods (a phylum of animals with jointed limbs and a hard chitinous exoskeleton) characterised by the possession of two pairs of antennae, one pair of mandibles (parts of the mouthparts used for handling and processing food) and two pairs of maxillae (appendages used in eating, which are located behind the mandibles). Includes crabs, lobsters, shrimps, slaters, woodlice and barnacles.
- Dorsal fin: the unpaired fin found on the back of the body of fish, or the raised structure on the back of most cetaceans.
- Lateral line: a row of receptors that can detect movement via vibrations in water. The receptors are typically embedded in the skin, and in fish they form a line along the sides of the body.
- Spawning: the production or depositing of large quantities of eggs in water.
IUCN Red List (April, 2011)