Cod belongs to a family of fish known as gadoids which includes species such as haddock, pollack, pouting and ling. It has a distinctive barbel below the lower jaw which it uses to search for food on the seabed. Cod is found all around the coasts of Britain and Ireland and is one of the UK’s most popular seafood’s. As a result it has been fished extensively in UK waters. Cod are often found in large dense shoals making them an easy target for fishermen.

In brief

• Widely distributed around the coast of Northern Ireland
• Found in a variety of habitats from the shoreline to >200m
• Listed as vulnerable on the global/European IUCN Red List, its population is declining in the Irish Sea
• Commercially valued seafood; sport fish for anglers, the waste and offal are used in fish meal, and the liver oil is used as a by-product
• Main threat from overfishing, while climatic imapcts affecting recruitment

Species description: Cod is a stout bodied fish with a muscular head and a fairly long chin barbel. It has relatively small eyes, three dorsal fins which are all close together at the base and two anal fins. The upper jaw overhangs the lower and the lateral line is continuous with a smooth curve above the pectoral fin. The tail can be square or rounded. The background colour of cod can vary from greenish to sandy brown with dark or light mottling on its back and sides, the underneath is white. Average cod measure about 120cm and weigh 11.3kg, the maximum reported age is 25 years. Cod usually forms shoals during the day, while at dawn and dusk searches for food on the seabed and mid-water. Adults eat crustaceans, worms, brittle stars and fish. Juvenile cod feed on small crustaceans.

Life cycle: Cod in the Irish Sea spawn from late February to early April, with spawning areas situated in coastal areas. Adults can make considerable migrations to spawning grounds, although little is known on their exact movements. The eggs are transported by currents before hatching after approximately 12 to 24 days, dependent on seawater temperatures. Older and larger cod have been found to produce larger eggs with neutral buoyancy, which is important for egg and larval survival. The age of maturity varies regionally being 3 years in the Irish Sea. Juvenile cod remain in the water column feeding on plankton before settling onto the seabed at about 50mm in length. Irish Sea cod are some of the fastest growing cod in the world, being close to the species southern range.

Similar species: Juvenile cod can look similar in shape and colouring to juvenile whiting (Merlangius merlangus). However cod has a chin barbel where whiting does not.

How to see this species: Cod is a deepwater species so is rarely seen in its natural habitat. It can however be viewed in the Exploris Aquarium, Portaferry. It can also be seen at fish markets or in the supermarket. Cod are targeted by sea anglers and codling (young cod) are often caught along our northern shore line.

Current status: The Irish Sea stock of cod has declined ten-fold since the late 1980’s and is well below safe biological limits as defined by fishery scientists.

Why is this species a priority in Northern Ireland?

• IUCN Red List status vulnerable
• Listed as a UK priority species
• Declining

Threats: The main threat to cod is overfishing. In previous years cod was significantly widespread and abundant. Since the 1980’s stocks of cod have been harvested unsustainably, as it is a long-lived species and currently has low recovery this makes it particularly vulnerable. Scientists advised in 2011 that if no action was taken cod was likely to become extinct in the next 10 years.
Due to the aggregating behaviour of cod it is still possible to find areas where there is a high density even at low abundance. This in turn can lead to high catches in specific areas and the possibility of low levels of fishing effort causing high numbers of cod being removed from the stock.
There is evidence that the reduction in the number of young cod produced by a specific stock per year could be due to a combination of reduced numbers of females old enough to reproduce and poor environmental conditions corresponding with above-average sea temperatures. The minimum landing size for cod in EU waters is 35cm however the approximate size at which 50% of females first spawn is 60-70cm. The removal of females before spawning reduces the ability of the stock to be replenished.

Action:

• ICES advises that zero catches be taken in 2012
• Council Regulation (EC) 1342/2008, The long term cod management plan, states Member States should introduce new mechanisms (alongside the fishing industry) to encourage fishermen to engage in cod-avoidance programmes, and to exercise their power to allocate access to fishing for cod stocks so as to encourage their fishermen to fish in ways that result in more selective fishing and are less harmful to the environment
• Undertake further research to understand climatic/recruitment processes

Objectives: Avoid eating cod from stocks which are depleted and where fishing is at unsustainable levels. The Marine Conservation Society’s ‘Good Fish Guide’ and the Marine Stewardship Council (MSC) have websites that can help consumer’s source sustainable seafood, see links below.

In addition anglers should adopt the catch and release programme in particular with large female cod.

Conservation:

• The cod fishery is currently managed through a combination of closed spawning areas, TACs and measures associated with days at sea and gear restrictions
• OSPAR List of Threatened and/or Declining Species and Habitats, 2008 for Cod in the Irish Sea
• NERC Act 2006 Species of Principal Importance in England (section 41) and Wales (Section 42)
• Northern Ireland Priority Species List, March 2010
• Scottish Biodiversity List of species of principal importance for biodiversity conservation
• UK list of Priority Habitats and Species
• IUCN Red List of Threatened Species 2007
• Included in the Grouped Species Action Plan for commercial marine fish

Distribution Map from NBN: Gadus morhua at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Gadus morhua at iNaturalist World Species Observations database.

WoRMS: Gadus morhua at World Register of Marine Species. Accepted name: Gadus morhua Linnaeus, 1758. AphiaID: 126436.

Literature:

Maitland, P.S. and Herdson, D. (2010). Key to the Marine and Freshwater Fishes of Britain and Ireland. Bristol; Environment Agency 204.

Classification: Biota; Animalia; Chordata; Vertebrata; Gnathostomata; Osteichthyes; Actinopterygii; Actinopteri; Teleostei; Gadiformes; Gadidae; Gadus