CPUE-based assessments of the Greenland halibut resource using SCAA

SCAA is used to assess the Greenland halibut resource as in Butterworth and Rademeyer (2009), but here using CPUE rather than surveys to provide indices of abundance. The approach is essentially that of an ASPM – a standard production model except that agestructure of the commercial catch is also taken into account. A base case (“Baseline CPUE”) is selected which allows variability over time in commercial selectivity-at-age sufficient in extent to eliminate most of the systematic patterns evident if this selectivity is kept temporally invariant. The resultant biomass trends estimated are quite similar to, though slightly steadier than those for the comparative survey-based assessment, with both showing recent increases. This contrasts with the XSA assessment for which the biomass estimates are much lower.