The Impact of Sea‐Ice Drift and Ocean Circulation on Dispersal of Toothfish Eggs and Juveniles in the Ross Gyre and Amundsen Sea. Issue 10 (4th October 2021)

• Record Type: Journal Article
• Authors: Behrens, Erik; Pinkerton, Matt; Parker, Steve; Rickard, Graham; Collins, Charine
• Is Part Of: Journal of geophysical research. Volume 126:Issue 10(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-10-04
• Subjects: Oceanography -- Periodicals; 551.4605
• DOI: 10.1029/2021JC017329
• Languages: English
• ISSNs: 2169-9275

Abstract

Abstract: 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 used 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 were released on seamounts of the Pacific‐Antarctic ridge in the Ross Gyre and advected using hydrodynamical model data. Particles were seeded annually over the years 2002–2016 and tracked for 3 years after their release. Recruitment success was evaluated based on the number of juveniles that reached known coastal recruitment areas, between the eastern Ross and Amundsen Seas, within 3 years. Sensitivities to certain juvenile behaviors were explored and showed that recruitment success was reduced by around 70% if juveniles drifted with sea‐ice during the second winter season as this carried them into the open ocean away from the shelf region. Recruitment success increased during the second winter season if juveniles were entrained in the Ross Gyre circulation or if they actively swam toward the shelf. These modeling results suggest that the ecological advantage of sea‐ice association in the early life cycle of toothfish diminishes as they grow, promoting a behavior change during their second winter. Plain Language Summary: The Antarctic toothfish, Dissostichus mawsoni, is a large, commercially harvested fish in the Southern Ocean. Hypotheses have been put forward around the importance of sea‐ice for their early life stage, which this study investigates. These fish lay buoyant eggs in the water column during winter season. Spawning locations have been identified around seamounts in the Ross Gyre. After spawning the buoyant eggs float to the surface where they drift with sea‐ice until they hatch. After hatching the juvenile fish are hypothesized to travel from the Northern Ross Gyre region to the continental shelf break between the eastern Ross and Amundsen Seas within 2–3 years. In this study, we investigate how ocean currents and sea‐ice drift influence their journey by using data from a high‐resolution ocean model. Simulations with different particle behaviors reveal that their recruitment success is around 70% lower if juveniles would continue to drift with sea‐ice instead of following ocean currents as juveniles. In particular, the modeled sea‐ice drift during the second winter season carries many juveniles away from the shelf break. Results suggest that the advantage of sea‐ice, providing food and shelter, diminishes as toothfish grow. Key Points: Particles drift from the northern Ross Sea and Southeast Pacific Basin to the continental shelf break as a part of the Ross Gyre circulation Recruitment success is 70% lower for particles which drift with sea‐ice, but particles reach the shelf break around 100 days earlier Sea‐ice advected particles are carried away from the shelf break, in the north‐eastern Ross Gyre during the second winter season