Hypothetical stock structure of Antarctic toothfish in the Pacific sector (FAO Statistical Area 88)

We review the stock structure of Antarctic toothfish Dissostichus mawsoni in Statistical Area 88 with the aim of characterising the likely stock boundaries relative to fishery management. We include information from studies examining genetics, otolith microchemistry, stable isotopes, tagging, size and age structures, growth dynamics, and particle dispersal simulations. A clear progression in the size and age of Antarctic toothfish from juveniles on the continental shelf to adolescents on the continental slope to adults on the Pacific Antarctic Ridge demonstrates the ontogenetic progression within the Ross Sea following the local bottom water currents in each area. Similar characteristics are observed in the Amundsen Sea and the Bellingshausen Sea but with some clear differences that suggest a high level of mixing of juveniles in the eastern Amundsen Sea and Bellingshausen Sea. The smallest fish (~60 cm) are not observed in the Ross Sea but are observed mainly near 1200 m in both the Amundsen and Bellingshausen Seas. Interestingly, 75–110 cm fish are not frequently observed in the Amundsen or Bellingshausen Seas. With few seamounts in the Bellingshausen Sea, adult fish are well represented on both the continental shelf and slope. Dispersal simulations from locations of adults suggest that Ross Sea juveniles recruit to the Amundsen continental slope, while Amundsen and Bellingshausen Sea juveniles are typically distributed to the continental slope of the Bellingshausen Sea. These patterns of pelagic advection during the first two years in the plankton followed by a slow, down-current ontogenetic migrations returning adults to deep seamount habitats over a 10–15 year period suggesting a metapopulation structure with largely resident regional adult populations with highly variable amounts of juvenile mixing.