Spatial overlap of krill-dependent predators and krill fishery catches and a proposal for subdivision of catch limits in Subarea 48.1

Progressing from Stage 1 to Stage 2 of a feedback management strategy requires a better understanding of spatial overlap between predators and fishing activity. We provide estimates of the spatial overlap in Area 48, with particular emphasis on Subarea 48.1. We used habitat utilization data for penguins (Adélie, chinstrap, and gentoo) and pinnipeds (Antarctic fur seals, Weddell seals, and leopard seals) based on data from satellite and light-based geolocation tracking studies.  Catch data were restricted to the last 5 years, since this time period emphasizes the shift toward autumn and winter fishing in Subarea 48.1. In general, overlap of summer and winter foraging habitats with krill catches in Subarea 48.1 was observed for all predators. Overlap was highest for predators that used coastal SSMUs during the winter period, especially in the Bransfield Strait. Across years, predator distributions appeared to be more stationary and did not respond as rapidly (or on as large a scale) to conditions that might affect the distribution of fishing effort.  A comparison of CEMP parameters from two years with large differences in total catch in Subarea 48.1 suggests plausible local impacts on gentoo penguin recruitment and reproductive investment. We note that such impacts arose when CM-51-07 was invoked to close the fishery and that 55% (85,000 tonnes) of the allocation to Subarea 48.1 (155,000 tonnes) was taken from a single SSMU. We propose that 85,000 tonnes, based on observed overlap and likely impacts of such concentrated catch on predators, represents a useful upper limit for subdivision of catch among SSMUs and that a Subarea limit of 155,000 tonnes provides a catch consistent with the objectives of Article II of the Convention.