Cod (Gadus morhua) catches and landings in the 1970s and 1980s were very large in comparison to today's fishery. However cod remains an important commercial species for Scottish fishermen, today cod is a small volume, but valuable by-catch to the Scottish demersal fleet, it accounts for only 8.2% of the tonnage of all fish and shellfish landed into Scotland by the Scottish fleet. Two main stocks of cod (the North Sea and West of Scotland) contributed to Scottish landings in 2010 of 11,750 tonnes worth just over £23.22 million. Very small catches are also made at Rockall. A variety of types of trawl nets are used to catch cod mainly in offshore areas at present. In the past inshore fisheries and local 'set net' fishing have been important; today however, they are no longer used to pursue cod.
Adult cod occur mainly in the northern and central areas of the North Sea with smaller populations in the south. Newly hatched cod are distributed over a large part of this area with high concentrations off the Jutland coast. One and two year old cod tend to over-winter in shallow coastal areas, but eventually disperse into deeper water. Whilst some cod tend to reside all year around in coastal areas, the larger offshore aggregations of cod tend to be migratory. Cod are also distributed throughout the west coast but occur mainly in the northern area. Tagging experiments have shown that cod from this region inter-mix with those in IVa, west of Shetland. In contrast, further south in areas such as the Clyde, cod appear to be largely resident all year round.
Many cod now reach maturity at two years old with 50% mature by 3 years old. By the time they reach five years, all cod are mature. An adult female of around 80 cm can produce around four million eggs in a season. Spawning mainly takes place between February and March with the largest spawning areas in the northern North Sea and around Dogger Bank. Spawning on the west coast takes place between January and April with a peak in March and occurs in most offshore areas. The major spawning area extends offshore from the Outer Hebrides although there are other important areas such as the Clyde.
Young cod live in the upper water layers for a period before moving to the seabed in July and August. They grow quickly and can reach 20cm after one year, 50cm after two years and 80cm by the time they are four years old. By the time they reach two years old, young cod are fully exploited by the commercial fishery as the minimum landing size for cod is 35cm. Many fish are caught before they have the chance to spawn and less than one twentieth of one year olds will survive to the age of four.
Cod do not usually browse for food on the bottom but are active feeders. By weight, around three quarters of the food of all sizes of cod consists of fish and crustaceans. The rest is made up of small quantities of molluscs and worms. As they grow, cod eat an increasing amount of fish. Sandeel, Norway pout, whiting, herring, dab and cod themselves are the main fish species eaten.
|North Sea||West Coast|
The ICES assessment in 2011 classifies the North Sea stock as suffering reduced reproductive capacity and being harvested unsustainably. The spawning stock biomass has been increasing steadily since its historical low in 2006, but is still estimated to be below Blim at 54,700 tonnes. Fishing mortality is estimated to be marginally above the precautionary reference point (Fpa) but is still well above the level which is consistent with achieving Maximum Sustainable Yield (MSY). The 2005 year class is estimated to be one of the most abundant amongst the recent below-average year classes.
West of Scotland
Based on the 2010 assessment, ICES classifies the west of Scotland cod stock as suffering impaired recruitment. Total mortality is high but cannot be accurately divided into fishing mortality and natural mortality. The spawning stock biomass has been increasing from an all time low in 2006, and is estimated to be just over 8700 tonnes. This biomass level is below both the precautionary reference point (Blim) and the level set for achieving MSY. Recruitment has been estimated to be low over the last decade. The 2005 and 2008 year classes are estimated to be the largest since 1997 and comparable with the long-term geometric mean.
The EU–Norway agreement management plan was updated in December 2008 to be consistent with the precautionary approach and is intended to provide for sustainable fisheries and high yield leading to a target fishing mortality to 0.4. The EU has adopted a long-term plan for this stock with the same aims.
ICES evaluated both plans in 2009 and considered them to be in accordance with the precautionary approach if implemented and enforced adequately. The effectiveness of the plan will be affected by TAC and effort overshoot and the consequent increase in discards. The evaluation assumed discarding rates as observed in 2008, an increase on this rate will reduce the effectiveness of the plan towards increasing
For further information a copy of the plan can be obtained from:
At the December 2011 meeting in Brussels, the Council of Ministers of the EU set the Total Allowable Catches for cod as follows:
North Sea 21,974 10,311
West of Scotland 0 0
A 1.5% by catch allowance has however been introduced for EU fleets fishing the West of Scotland stock. This quota decision was reached in response to the recommendation that only catches reduced to the lowest possible levels are compatible with the MSY and precautionary approaches and in light of difficulties in separating fishing mortality from natural mortality.
These quota decisions are consistent with the existing cod long term management plans (LTMP) and includes an effort management scheme which limits the effort available to the main cod catching gears. The Council Regulation covering the plan also includes provision for applying management measures to reduce cod mortality without reducing effort. The UK interpretation of permissible effort 'buy back' under the Conservation Credits Scheme (effort levels can be reinstated up to the level of the baseline established at the start of the scheme) was upheld. In accordance with the cod LTMP a further 10% cut in effort (before buy back) from the baseline applies in 2012. To justify existing and future effort buy back the UK is committed to the introduction of highly selective gears in both finfish and Nephrops targeted fleets. For the West of Scotland the UK also committed to introducing spatial measures to separate catches of cod and other gadoids from 1st January 2012.
A number of initiatives are in place for improving our understanding of cod and the management of mixed fisheries which take it in their catches. Ongoing regular survey and assessment work by Marine Scotland - Science (MSS) is supplemented by a number of research projects into the reproduction and stock structure of cod. Additionally, the Scottish Government is funding four full time observers over a two year period to assist in concentrated data collection in the Scottish demersal sector.
MSS, in collaboration with NRC Europe, is currently carrying out research on the effects of predation by seals on the cod population to the west of Scotland.
In February 2008 Scotland implemented a national scheme known as the 'Conservation Credits Scheme'. The principle of this two-part scheme involves additional time at sea in return for the adoption of measures which aim to reduce mortality on cod and lead to a reduction in discard numbers. ICES notes that from the initial year of operation (2008) cod discarding rates in Scotland have decreased from 62% to 36% in 2010. In 2010 there were 165 closures, and from July 2010 the area of each closure increased (from 50 square nautical miles to 225 square nautical miles).
Recent work tracking Scottish vessels in 2009 has concluded that vessels did indeed move from areas of higher to lower cod concentration following real-time closures during the first and third quarters (there was no significant effect during the second and fourth quarters).