Second winter survey of Antarctic toothfish (Dissostichus mawsoni) in the Ross Sea region

The second winter survey for Antarctic toothfish (Dissostichus mawsoni) in the Ross Sea region was conducted by the FV Janas during September and October 2019. The survey followed the northern extent of sea ice from SSRU 882B through 881B. Antarctic toothfish sampled during this survey were in spent condition by the beginning of September, gonadosomatic indices were less than 5%, suggesting spawning had ended by mid-August. Eggs collected from the plankton were at the eyed-embryo stage, comparable with day 15 of D. eleginoides development. Buoyancy was similar to newly fertilised eggs indicating a near-surface distribution. Four D. mawsoni were tagged and released with Pop-off Satellite Archival Tags provided by NOAA to examine movement patterns of adults in the region. Four adult D. mawsoni released with conventional tags during commercial fishing on the Ross Sea slope were recaptured more than 2300 km away on a seamount in SSRU 882B. Species composition and density were correlated with oceanographic variables and structured by location with respect to the Pacific Antarctic ridge.