An initial examination of using CPUE as a fishery performance index for the krill fishery

Early analyses of CPUE in the krill fishery concluded that it was not a useful index of krill abundance. However, understanding the factors effecting the operation of the krill fishery and the extent to which these reflect changes in krill abundance are key elements of developing feedback management of the krill fishery. This analysis reviewed catch and effort data from the krill fishery for the period 2001 – 2016 (up to 26/5/2016) in Subareas 48.1, 48.2 and 48.3 to determine whether CPUE might be used to produce a fishery-scale performance index. The vessels-specific mean CPUE (log catch (kg) per minute fishing) was estimated using all data for each vessel; an annual index was calculated as the difference between this overall mean and the mean for each year in which the vessel fished. An overall fishery performance index (FPI) was derived from the sum of the vessel-specific indices for each year. The annual FPI for each of the three subareas showed no synchronous relationship with each other and showed differing relationship with the total catch in the same subarea. Comparison of the annual FPI with the krill biomass (from research surveys) and the CSIs from CEMP data suggests (at least qualitatively) some concordance between the performance of the fishery and krill abundance.