Report of the Working Group on Mixed Fish-eries Advice for the North Sea (WGMIXFISH-NS). 20-24 May 2013 ICES Headquarters, Copenhagen

Type Expertise
Date 2013-05
Language English
Ref. ICES CM 2013/ACOM:22
Other localization
Author(s) ICES
Contributor(s) Vermard YouenORCID
Sponsor CIEM / ICES
Abstract The ICES’ Working Group on Mixed Fisheries Advice for the North Sea [WGMIXFISH-NS] (Chair: Steven Holmes (UK)) met at ICES HQ, 20-24 May 2013 to apply mixed fisheries forecasts to the draft North Sea single species advice formed by WGNSSK 2013.
The meeting has produced a North Sea Mixed Fisheries Advice sheet and included lines showing mixed fisheries scenario outcomes in the single species advice sheets (for those stocks considered) for consideration by the ACOM advice drafting group. The North Sea Mixed Fisheries Annex is a separate document with minor updates from last year.
The mixed fisheries runs followed the approach used by ICES; management plan where it exists and MSY approach otherwise. The species considered here as part of the demersal mixed fisheries of the North Sea are cod, haddock, whiting, saithe, plaice, sole, and Nephrops norvegicus. The plaiceVIId and soleVIId stocks were added to the full scenario calculations. All of these are now subject to multi-annual man-agement plans apart from plaiceVIId, soleVIId and Nephrops. Five scenarios were considered.
1 ) max: The underlying assumption was that fishing stops when all quota species are fully utilised with respect to the upper limit corresponding to single stock exploitation boundary.
2 ) min: The underlying assumption was that fishing stops when the catch for the first quota species meets the upper limit corresponding to single stock exploitation boundary.
3 ) cod: The underlying assumption was that all fleets set their effort at the level corresponding to their cod quota share, regardless of other stocks.
4 ) sq_E: The effort was set as equal to the effort in the most recently recorded year for which there are landings and discard data.
5 ) Ef_Mgt: The effort in métiers that used gear controlled by the EU effort management regime had effort adjusted according to the regime.

The max and min scenarios were included to bracket the space of potential catch and SSB outcomes but for most fleets are considered unrealistic scenarios. Of the remain-ing scenarios none was picked as a preferred scenario. Effort limits under the EU ef-fort management regime were left unchanged in 2013 and the WG considered the relationship between F and effort changes under the long term management phase of the cod recovery plan open to interpretation but still included the scenario, having made its own interpretation of the control rule.
In a change to previous years, the intermediate year made use of the status quo effort scenario before application of the alternative scenarios in the advice year., (previously each scenario was applied in both intermediate and advice year). The change was considered to better reflect the assumptions on fleet behaviour used in the majority of single species short term forecasts.
The impact of mixed fisheries scenarios on two stocks, northern hake and plaice 3aN were considered without their incorporation into the mixed fisheries projections. The Plaice 3aN TAC is predicted as underutilised even under assumption of status quo effort. The North Sea quota of Northern Hake is predicted to be underutilised under the min, cod and Ef_Mgt scenarios but assuming status quo effort leads to prediction of over quota landings.
As a cross check, the landings by national fleets were summed over nation for each scenario, and the share by country was compared with the initial values input to the model. In general the results indicate that the approach used does not lead to viola-tion of the underlying hypothesis of relative stability in TAC sharing (quotas) across nations. Only minor deviations are observed across scenarios, except for the Ef_Mgt scenario. Here the fact the majority of Scottish vessels come under the scope of the EU effort management regime whereas Norwegian vessels are unaffected by the same regime leads to a shift of landings share from the former to the latter under the as-sumptions of the model.
As in 2012 data for this WG was requested as part of a joint WGNSSK-WGMIXFISH data call which allows a greater consistency between catch totals supplied to WGMIXFISH and WGNSSK. As an addition to its terms of reference the group also considered the consistency between the data supplied to this WG and that supplied to STECF for comparable fleet categories.
The WG wished to consider more stocks that straddle ICES areas IV and VI and in 2013 a new joint WGCSE-WGMIXFISH data call was issued (this covered e.g. An-glerfish and Megrim in IV and VI). Time pressures were such, however, that it was not possible to consider a second set of data files. The WG considers the best solution is a single joint WGCSE-WGNSSK-WGMIXFISH data call. This would also ensu
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How to cite 

ICES (2013). Report of the Working Group on Mixed Fish-eries Advice for the North Sea (WGMIXFISH-NS). 20-24 May 2013 ICES Headquarters, Copenhagen. CIEM / ICES, Ref. ICES CM 2013/ACOM:22, 115p.