Feeding and trophic ecology of Antarctic toothfish Dissostichus mawsoni in the Amundsen and Dumont D’Urville Seas (Antarctica)

Fisheries ecosystem-based management is an important tool for sustainable harvesting of fisheries worldwide. Knowledge of trophic interactions is crucial since changes in trophic balances can induce severe changes in the structure of marine communities. While advocated for deep-sea fisheries, a lack of studies in the benthopelagic area persist. The Antarctic toothfish, Dissostichus mawsoni, is a top predator inhabiting the Southern Ocean deep-sea and a high-value species in a fishery managed by CCAMLR (Commission for the Conservation of Antarctic Marine Living Resources). Previous studies suggested a geographical variability in its diet, but never studying it in the same year. We analysed stomach contents and stable isotopes of δ15N and δ13C in the muscle of D. mawsoni captured in three fishing areas from the Amundsen and Dumont D’Urville Seas, during the 2016/17 fishing season. Although significant spatial differences were found, five taxa were found in all sites, Antimora rostrata, Macrourus spp., Muraenolepis spp., Moroteuthopsis longimana and Psychroteuthis glacialis. High diversity of prey confirms D. mawsoni as a generalist feeder. Values of δ15N showed similar trophic position across areas, in contrast to the differences found in δ13C values. GLM showed that δ15N and δ13C values varied with otolith length, latitude and the opposite isotope, i.e. δ13C and δ15N respectively. Implications for D. mawsoni fisheries management are discussed considering different predation release scenarios.

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