Fisheries and Resources Monitoring System

Plaice - Western Channel
Marine Resource  Fact Sheet
ICES Advice 2012
Plaice - Western Channel
Fact Sheet Citation  
Plaice in Division VIIe (Western Channel)
Owned byInternational Council for the Exploration of the Sea (ICES) – More
Related observationsLocate in inventorydisplay tree map
FAO Names: en - European plaice, fr - Plie d'Europe, es - Solla europea, ru - Камбала морская
Geographic extent of Plaice - Western Channel
Main Descriptors
Considered a single stock: Yes        Spatial Scale: Sub-Regional
Management unit: No        Reference year: 2012
Biological State and Trend
State & Trend Descriptors
Exploitation rateAbove targetHigh fishing mortality
Abundance levelAbove triggerIntermediate abundance

The large reduction of F in 2009 is confirmed in subsequent years’ estimates, but remains well above FMSY. SSB has increased in the last three years and is currently well above MSY Btrigger due to the large recruitment in 2010. The recent dynamics of the stock has caused a revision of MSY Btrigger.
Habitat and Biology
Depth zone: Shelf (50 m - 200 m).   Vertical distribution: Demersal/Benthic.  

Plaice aggregate at spawning grounds in the 1st quarter of the year. The condition factor for plaice is highest in summer/autumn on the more dispersed feeding grounds. Tagging studies show spawning migrations from Division VIIe to VIId during the 1st quarter of the year. It is assumed that 15% of the 1st quarter plaice catch in Division VIId consists of fish from Division VIIe. Suitable sites for nurseries are located in shallow waters, close to fresh and cool seasonal water inflow.
Geographical Distribution
Jurisdictional distribution: Shared between nations

Water Area Overview
Spatial Scale: Sub-Regional

Ecoregion: Celtic Sea and West of Scotland.
Geo References
Resource Structure
Considered a single stock: Yes

The fisheries

Plaice are taken as a bycatch in the beam trawl fishery mainly targeting sole and anglerfish, and as part of a mixed demersal fishery by otter trawlers. The main fishery is south and west of Start Point. Although plaice are taken throughout the year, the larger landings are usually during February, March, October, and November. Discarding appears to be higher in quarters 1 and 2 in this fishery, but is low compared to other plaice stocks.
Catch distribution

Landings in 2011 were 1332 t (55% beam, 40% otter (dem), 2% gillnets, and 3% other gear (mostly caught by the above gears, but not available separately by all countries). In addition, 173 t landed from Division VIId are included in the assessment, reflecting the 15% Q1 migration correction (unknown gear).

Total catch (2011) = 1505 kt, where 100% were landings (no discards, industrial bycatch, or unaccounted removals)

Effects of the fisheries on the ecosystem

Beam trawling, especially using chain-mat gear, is known to have a significant impact on the benthic communities, although less so on soft substrates and in areas which have been historically exploited by this fishing method. Some beam trawlers are experimenting with benthic drop-out panels that release about 75% of benthic invertebrates from the catches. Full square mesh codends are being tested in order to reduce the capture of benthos further and improve the selection profile of gadoids.
Scientific Advice

ICES advises on the basis of the transition to the MSY approach that landings of plaice in Division VIIe in 2013 should be no more than 2100 t.
Overall Assessment Results
Figure Plaice in Division VIIe (Western Channel). Summary of stock assessment (weights in thousand tonnes). Predicted recruitment values are shaded. Top right: SSB and F for the time-series used in the assessment.
Assessment Model

Quality consideration

There is uncertainty about the stock structure due to migration between this area and the Eastern Channel during the spawning period, which is now partially corrected for in the assessment by an added element of Division VIId catches and age information to account for migration (ICES, 2010). There is a heavy reliance on the age composition data derived from UK(E+W) sample data. Discards are not included in the assessment. Discard rates of plaice in Division VIIe are much lower compared to other plaice stocks and their omission is unlikely to significantly alter SSB and mortality trends.

This assessment would benefit from the addition of age composition information from both the French and Belgian fleet who collectively account for 30% of the total landings for this stock. Including discard estimates would also improve the assessment.
Figure Plaice in Division VIIe (Western Channel). Historical assessment results (final-year recruitment estimates included). The stock was benchmarked in 2010, resulting in the step change in the SSB in this plot.

Scientific basis

Assessment type Age-based analytical assessment (XSA).
Input data One fishery independent survey index (UK-WEC-BTS); one industry–science survey (FSP-7e UK-(E+W)); three commercial lpue indices (UK WECOT, UK WECBT, UK WECOT historical).
Discards and bycatch Not included in the assessment.
Indicators None.
Other information Benchmarked in 2010 (WKFLAT 2010).
Working group report WGCSE
Management unit: No

Management plans

No specific management objectives are known to ICES.
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. Plaice in Division VIIe (Western Channel). Report of the ICES Advisory Committee, 2012. ICES Advice, June 2012. Click to open
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