Report of the Second Inter-Benchmark Protocol on West of Channel Flatfish (IBPWCFlat2), June–September 2015, by correspondence
The first inter-benchmark for plaice and sole in VIIe (IBPWCFlat) took place at the start of 2015. A second inter-benchmark in the same year (IBPWCFlat2) was necessary for the following reasons:
•WKPLE (ICES, 2015a) revised the assumed rate of migration of place be-tween Divisions VIId and VIIe. This resulted in a change in the catch numbers-at-age and weights-at-age (some of the catches of mature fish taken in VIId during quarter 1 are assumed to belong to the VIIe stock). WGCSE (ICES 2015c) was unable to make these changes to the numbers and weights-at-age due to time constraints.
•WGCSE (ICES, 2015c) raised doubts about the raising procedures for the UK FSP and Q1SWBeam survey indices, which needed to be investigated.
•The way fishing effort is recorded in the UK e-logbooks has changed recently, therefore the calculation of effort for the commercial tuning fleets needed to be revised.
IBPWCFlat2 addressed the issues above and agreed on new XSA input data and model settings for both stocks. However, the assessment for the plaice stock had large retrospective patterns and the FMSY reference point calculated from this model was considerably higher than that of neighbouring stocks. These issues led the group to advise that the plaice assessment should not be used in an absolute sense but as an indication of trends only until the source of the retrospective pattern is better under-stood. The sole assessment and reference points were accepted by the group. The protocol for the forecast was agreed. Both stock annexes have been updated.
Published under the auspices of the following ICES Steering Group or Committee