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 long before they have the chance to spawn and less than one twentieth of one year olds will survive to the age of four. This means the stock is particularly vulnerable to an on-going reduction of the spawning component.

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

Based on the 2009 assessment, ICES classifies the west of Scotland cod stock as suffering reduced reproductive capacity. Total mortality is high but cannot be accurately divided into fishing mortality and natural mortality. The spawning stock biomass has increased from an all time low in 2006, but remains well below Blim. Recruitment has been estimated to be low over the last decade. The 2005 year class is estimated to be the largest for that decade, but still below the long-term average.

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 the management plan in 2009 and considered it to be in accordance with the precautionary approach if it is 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 the spawning stock biomass.

The plan stipulates that, based on the assumption that the 25% reduction in F in 2009 has been effective in reducing F2009 to 25% below F2008, the following criteria be met, in order of increasing priority:

(a) TAC2009 should not exceed a level that results in F2010 being above 65% of F2008

(b) There should be no more than a 20% change from TAC2009 to TAC2010

On the basis of the management plan, ICES advised on an F in 2010 that would be 65% of the F in 2008 (F2010 = 0.51), implying that total catches should be less than 66,400 tonnes. Assuming that the discard rates are as observed in 2008, this would imply landings of less than 40,300 tonnes in 2010. This presumes that the objectives of the management plan are realised which assumes reduction in F and control of catches in 2009 and 2010.

Given the low stock size and recent poor recruitment, the stock cannot be rebuilt to Bpa at the start of 2011 even with a zero catch. Simulations indicate that with the recent poor recruitment, a zero catch in 2010 and 2011 is likely to achieve the rebuilding of the stock to Bpa by 2012.

ICES observed that there have been considerable problems with the effectiveness of the former recovery plan. Despite the objective of the plan to reduce fishing mortality and to increase the spawning stock biomass by combined TAC control and effort management, estimated catches have been much higher than intended in the management plan. Although fishing mortality has been reduced after 2000, it has remained well above the targets implied by the plan and has increased again in 2008. Also discarding increased in 2007 and 2008 and contributed about half of the total fishing mortality in these years. Under the present implementation and enforcement approach, reduction in F and the recovery of the stock is unlikely under either management plan. It is therefore urgent to make significant improvements in implementation and enforcement to achieve reduction in F by effective control of cod catches.

The west of Scotland cod stock is also managed by the European Union long-term plan (Council Regulation (EC) 1342/2008), which replaces the recovery plans in Regulation (EC) No 423/2004, and has the objective of ensuring the sustainable exploitation of the cod stocks on the basis of maximum sustainable yield while maintaining a target fishing mortality of 0.4 on specified age groups.

Since it is not possible at present to assess unaccounted mortality accurately, ICES cannot yet evaluate if the management plan is in accordance with the precautionary approach. Due to the uncertainty in the level of fishing mortality, it is also not possible for ICES to provide any quantitative forecasts. An exploratory forecast was performed to consider projections of spawning stock biomass. Even under zero removals it was predicted that SSB would still be below Blim in 2011.

The stock is suffering impaired recruitment. SSB is very low. It is necessary to reduce all sources of fishing mortality to recover the stock above Blim as quickly as possible. Management measures taken thus far have not recovered the stock.

There are indications that because of new legislation, misreporting has reduced from the beginning of 2006. Coincident with this, data show increased discards at ages one and two and a change in discard practices such that fish are discarded at older ages. This suggests the legislation has controlled landings rather than catch.

For the management plan to succeed in recovering the cod stock in VIa, whilst maintaining mixed fisheries, it will be necessary to have well-targeted effort control for fleets with cod by-catches whilst reducing the by-catches of cod to as close to zero as possible. This could be most reliably achieved through the provisions of Chapter III of the plan, particularly through avoidance schemes and the use of highly selective gears. The success of these measures requires close collaboration with the fishing industry and sufficient industry uptake and compliance with new measures.

For further information a copy of the plan can be obtained from:

http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2008:348:0020:0033:EN:PDF

The advice for this year remains the same as last year and ICES advises that no fishing should take place for cod in Division VIa.

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.

New projects under the Scottish joint industry science partnership (SISP) are looking at survey gear performance with respect to cod and other gadoids, utility of existing closed areas for the protection of cod and collection of fishermen’s knowledge on the distribution of spawning areas and juvenile grounds. As part of the SISP, MSS in partnership with the Scottish White Fish Producers Association, initiated a project in 2007 assessing the effectiveness of the Windsock closed area (VIa) on cod stocks. A survey of the area using a chartered commercial fishing vessel took place in March 2008. Analysis of the data is in progress.

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.