University Of Tasmania
136429 - Finding mesopelagic prey in a changing Southern Ocean.pdf (1.66 MB)
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Finding mesopelagic prey in a changing Southern Ocean

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journal contribution
posted on 2023-05-20, 09:06 authored by Clive McMahonClive McMahon, Mark HindellMark Hindell, Charrassin, J-B, Stuart CorneyStuart Corney, Guinet, C, Harcourt, R, Jonsen, I, Rowan TrebilcoRowan Trebilco, Guy Williams, Sophie BestleySophie Bestley
Mesopelagic fish and squid occupy ocean depths extending below the photic zone and their vertical migrations represent a massive pathway moving energy and carbon through the water column. Their spatio-temporal distribution is however, difficult to map across remote regions particularly the vast Southern Ocean. This represents a key gap in understanding biogeochemical processes, marine ecosystem structure, and how changing ocean conditions will affect marine predators, which depend upon mesopelagic prey. We infer mesopelagic prey vertical distribution and relative abundance in the Indian sector of the Southern Ocean (20° to 130°E) with a novel approach using predator-derived indices. Fourteen years of southern elephant seal tracking and dive data, from the open ocean between the Antarctic Polar Front and the southern Antarctic Circumpolar Current front, clearly show that the vertical distribution of mesopelagic prey is influenced by the physical hydrographic processes that structure their habitat. Mesopelagic prey have a more restricted vertical migration and higher relative abundance closer to the surface where Circumpolar Deep Water rises to shallower depths. Combining these observations with a future projection of Southern Ocean conditions we show that changes in the coupling of surface and deep waters will potentially redistribute mesopelagic prey. These changes are small overall, but show important spatial variability: prey will increase in relative abundance to the east of the Kerguelen Plateau but decrease to the west. The consequences for deep-diving specialists such as elephant seals and whales over this time scale will likely be minor, but the changes in mesoscale vertical energy flow have implications for predators that forage within the mesopelagic zone as well as the broader pelagic ecosystem.


Australian Research Council


Publication title

Scientific Reports



Article number









Institute for Marine and Antarctic Studies


Nature Publishing Group

Place of publication

United Kingdom

Rights statement

© The Author(s) 2019. Licensed under Creative Commons Attribution 4.0 International (CC BY 4.0)

Repository Status

  • Open

Socio-economic Objectives

Assessment and management of coastal and estuarine ecosystems; Biodiversity in Antarctic and Southern Ocean environments