Habitat and Biology
Depth zone: Shelf (50 m - 200 m). Vertical distribution: Demersal/Benthic.
Cod are widely distributed throughout the North Sea, but there are indications of sub-stocks. Genetic studies have indicated two subpopulations with long-term differences in recruitment trends, and largely inhabiting different regions of the North Sea, with cod from the deep-water subpopulation not expected to re-colonize depleted areas in the southern North Sea. Environmental influence on the stock
Recent recruitments have been low, possibly influenced by changes in the availability of food resources for cod larvae and increasing predation pressure. There is evidence of cannibalism and seal predation. Multispecies model runs estimate a decrease in cannibalism rates for age 1 and age 2 cod at current low stock levels, while seal predation on ages 3 to 6 has increased over the years due to an increase in seal abundance. Harbour porpoises also take a substantial amount of cod up to age 3.
Jurisdictional distribution: Shared between nations
Considered a single stock: Yes
Cod are taken by towed gears in mixed demersal fisheries. Cod are targeted by some fleets, but are also caught as part of a mixed fisheries catching haddock, whiting, Nephrops, plaice, and sole. Cod discards relative to catch have declined from the highest on record in 2008 to a just above the historical average in 2011 (from 50% to 25%, weight of cod discarded from the total estimated cod catch). Catch distribution
ICES estimates total removals (2011) at around 67 kt, with 35 kt estimated landings (59% demersal trawls and seines >100 mm, 16% gillnets, 10% Nephrops trawls 70–99 mm, and 6% beam trawls) and 11.7 kt estimated discards. Unallocated removals are estimated at around 43% (between 16% and 77%) of the catch in 2011. Effects of the fisheries on the ecosystem
The gillnet fishery for cod takes bycatches of harbour porpoise. Since 2001, effort reductions in this fishery have likely led to decreased bycatches. Hiddink et al. (2006) estimates that in areas of bottom trawl activity in the North Sea, benthic biomass and production is reduced by 56% and 21%, respectively, compared with an unfished situation.
ICES advises on the basis of the EU–Norway management plan that landings in 2013 should be no more than 25 441 t.
Overall Assessment Results
|Figure 18.104.22.168 Cod in Subarea IV (North Sea) and Divisions VIId (Eastern Channel) and IIIa West (Skagerrak). Summary of stock assessment with point-wise 95% confidence intervals, catch estimated, and adjusted for unallocated removals (from 1993). Weights in tonnes. |
Assessment ModelQuality consideration
The overall reporting (in particular through fully documented fisheries) of catch data provided to ICES has improved in 2012. The main sources of uncertainty are the estimation of unallocated removals and the assumption of fishing mortality in 2012 in the advice forecast.
| Cod in Subarea IV (North Sea) and Divisions VIId (Eastern Channel) and IIIa West (Skagerrak). Historical assessment results (final-year recruitment estimates included). |
A state–space age-structured assessment model with estimates of unaccounted removals (SAM).
One survey index (from IBTS Q1 survey).
Discards and bycatch
Included in the assessment (since 2004).
Latest full benchmark was performed in 2009 with an inter-benchmark meeting in 2011.
Working group report
Management unit: YesManagement plans
The EU–Norway agreement management plan was updated in December 2008 (Annex 6.4.2), and will be re-considered during 2012. The EU has adopted a long-term plan for this stock with the same aims (Council Regulation (EC) 1342/2008)
. ICES evaluated the plans in 2009 and concluded that they are both in accordance with the precautionary approach if implemented and enforced adequately.
Biological State and Trend
|Figure 22.214.171.124 - MSY |
There has been a gradual improvement in the status of the stock over the last few years. SSB has increased from the historical low in 2006, but remains just below Blim. Fishing mortality declined from 2000 and is now below Fpa, but is estimated to be well above FMSY. Recruitment since 2000 has been poor. The proportion of discards is still high relative to the historical period.
Source of information
The above excerpts are from the first two pages of the ICES advice, the supporting information to this advice can be read in full at the following reference:
ICES. Cod in Subarea IV (North Sea) and Divisions VIId (Eastern Channel) and IIIa West (Skagerrak). Report of the ICES Advisory Committee, 2012. ICES Advice, June 2012. http://www.ices.dk/committe/acom/comwork/report/2012/2012/cod-347.pdf