Evaluating a CPUE by seabed area analogy approach to estimate by-catch limits for macrourids in toothfish fisheries

We review the applicability of the CPUE by seabed area analogy method for the estimation of bycatch limits for macrourids for toothfish fisheries in the Convention Area with limited macrourid data. We examine the assumed relationship between longline CPUE and macrourid survey biomass in the Ross Sea, macrourid selectivity by gear type, and the effect of species composition on productivity parameters that influence the calculation of bycatch limits. We show that the ratio of macrourid CPUE to survey density is not constant, that vessels using different gear types report different CPUE values that do not vary with survey density in the same way, and that the productivity parameters used to estimate precautionary exploitation rates vary among species and species composition varies among fisheries.