A Comparison between XSA and SCAA Assessments of Greenland Halibut based on the Same Input Data

A number of variants of the SCAA are compared with results from the XSA assessment of Healey and Mahe (2009), where the SCAA uses the same data as for that XSA assessment. Differences in estimates of recent exploitable (B5-9) biomass trends – up for SCAA and down for XSA – are found to be largely resolved by introducing F-shrinkage in the SCAA, similar to the approach used for the NAFO XSA. Greater agreement still, including for the 10+ biomass (B10+) is obtained by forcing the commercial 11+ selectivity to be flat and at its level for XSA in the SCAA assessment. However both these adjustments to the SCAA come at the expense of appreciable deterioration in the fit of the SCAA model to the data as measured by the likelihood.