This report is one of two reports to the STECF of EWG 11-01 of the STECF Expert Working Group on management plans, (28 February to 4 March 2011) and provides an Impact Assessment report on the Bay of Biscay sole fisheries. It summaries biological modelling of a range of different stock dynamics incorporating uncertainty in stock recruitment function and measurement error. The results from an integrated bio-economic model showing economic impact on the sole fishery in the Bay of Biscay are presented. The simulations carried out show that a target F of 0.26 (Fmsy ) can be accepted as precautionary in the long term. Target Fs between 0.15 and 0.35 will give yields within 5% of yield at F=0.26. Economic considerations suggest that the management plan is expected to have slight long term gains and short term negative economic impacts for all the fleets involved in the sole fishery. The economic viability of fleets is not endangered and effort reallocation is expected to offset losses although it is difficult to predict such reallocation. The report provides details of approaches that could be used if the ICES assessment fails. The report has been endorsed by the STECF during its 36th plenum in April 2011.