Report of the Working Group on Mixed Fisheries Advice for the North Sea (WGMIXFISH). 2012

Type Expertise
Date 2012-05
Language English
Ref. ICES CM 2012/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 [WGMIX-FISH] (Chair: Steven Holmes (UK)) met at ICES HQ, 21-25 May 2012 to apply mixed fisheries forecasts to the draft North Sea single species advice formed by WGNSSK 2012.
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 unchanged from last year and is a separate document.
The mixed fisheries runs followed the approach used by ICES; management plan where it exists and MSY framework 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. All of these are now subject to multi-annual management plans apart from 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.
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 the 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 assumptions of the model.
Data for this WG was requested as part of a joint WGNSSK-WGMIXFISH data call issued formally under the EU DCF regulations. This has allowed a greater consis-tency between catch totals supplied to WGMIXFISH and WGNSSK. Problems in data supply were still encountered, however, caused primarily by the level of fleet disag-gregation best suited to the mixed fisheries projections being incompatible with na-tional sampling schemes (and the need to keep the number of fleet-metier combinations used in the ICES database - InterCatch - to a manageable number).
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