A multi-disciplinary approach incorporating otolith chemistry, age data and numerical Lagrangian particle simulations indicated a single, self-recruiting population of Antarctic toothfish (Dissostichus mawsoni) in the Southeast Pacific Basin (SPB) and Ross Sea, with a life history structured by the large-scale circulation. Chemistry deposited prior to capture along otolith edges demonstrated strong environmental heterogeneity, yet the chemistry in otolith nuclei, deposited during early life, showed no differences. Age data showed only adult fish in catches on the Pacific-Antarctic Ridge in the SPB; and structuring of life stages consistent with transport pathways from the northern Ross Sea. Lagrangian particle simulations predicted that early life stages following the flow in the SPB would be transported to areas in the Ross Sea where juveniles are caught; whereas, the circulation would facilitate adult movement along the shelf slope and back into the SPB where spawning adults are caught. These results suggest that: successfully spawning fish spend only a part of their adult life history in the Ross Sea; areas in the eastern Ross Sea contribute disproportionately to the spawning population; and areas in the southwestern Ross Sea may supply fisheries in the southern Indian Ocean.
Abstract:
In 2010, POKER Biomass survey was undertaken at Kerguelen Islands (Division 58.5.1) to collect information of all the fish species including the mackerel icefish, Champsocephalus gunnari. Data from this random stratified trawl survey, added to the previous results of 2006, was used for a short term assessment of C. gunnari on Kerguelen EEZ. The standard CCAMLR methods were used to provide potential yields for the 2010/2011 and 2011/2012 seasons even if fishery doesn’t occur presently. A catch limit tonnes was simulated till the 2011/2012 season.
