The impact of sea-ice drift and ocean circulation on dispersal of toothfish eggs and juveniles in the Ross Gyre and Amundsen Sea – Erik Behrens, National Institute of Water and Atmospheric Research

October 20, 2021 @ 9:00 am – 10:00 am
British Antarctic Survey
Dr. Shenjie Zhou

Knowledge about the early life history of Antarctic toothfish (Dissostichus mawsoni) is still incomplete, particularly on the spatial and temporal extent of spawning and the subsequent transport of eggs, larvae, and juveniles from the offshore spawning areas to the continental shelf. This study uses a high-resolution hydrodynamic model to investigate the impact of ocean circulation and sea-ice drift on the dispersal of eggs, larvae, and juvenile Antarctic toothfish. The virtual eggs are released on seamounts of the Pacific-Antarctic ridge in the Ross Gyre and advected using hydrodynamical model data. Particles are seeded annually over the years 2002 to 2016 and tracked for three years after their release. Recruitment success has been evaluated based on the number of juveniles that reached known coastal recruitment areas, between the eastern Ross and Amundsen Seas, within three years. Sensitivities to certain juvenile behaviours has been explored and showed that recruitment success was reduced by around 70% if juveniles drifted with sea-ice during the second winter season as this carries them into the open ocean away from the shelf region. Recruitment success increases during the second winter season if juveniles are entrained in the Ross Gyre circulation or if they actively swam towards the shelf. These modelling results suggest that the ecological advantage of sea-ice association in the early life cycle of toothfish diminishes as they grow, promoting a behaviour change during their second winter.

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