MethodologyScientific basisData and methods
An age-based analytical assessment (XSA) was conducted based on landings and indices from two surveys (ending in 2002) and two commercial fleets. Discard information is not included in the assessment. No recruitment indices are available for this stock. Information from the fishing industry
A meeting with representatives of the fishing industry in France was held prior to the Working Group meeting to present the data used to assess the Bay of Biscay sole stock. The participants did not express reservations on these data. Uncertainties in assessment and forecast
There is a need for fisheries independent data to improve the stock assessment and the estimation of recruitment. This assessment relies on times series of commercial fleets. In addition, the proportion of landings taken by these fleets is decreasing. Commercial data do not provide reliable estimates of incoming year classes. The catch and SSB in the forecast is dominated by year classes for which geometric mean recruitment is assumed.
Presently, different age reading methodology and age interpretation exists between nations involved in the fisheries.
Available discard data are patchy and noisy. The effect of excluding discard data from the assessment is currently unknown.Environment conditions
Environmental conditions have a large influence on catches of the fixed-net fishery in the first quarter. Environmental conditions were especially favourable in 2002.
Studies in Vilaine Bay showed a significant positive relationship between the fluvial discharges in winter–spring and the size of the local nursery. The extent of the river plume influences both the larval supply and the size and biotic capacity of habitats in estuarine nursery grounds and determines the number of juveniles produced. This localized effect is not apparent on the scale of the whole Division VIIIa,b,d stock and the impact of this relationship was therefore not taken into account in stock projections. Comparison with previous assessment and advice In this year’s assessment SSB in 2008 has been revised upward by 8% and F in 2007 has been revised downwards by 17% compared to last year assessment. Last year’s advice was based on Fpa. This year´s advice is based on precautionary considerations that SSB in 2011 should not be allowed to decrease.