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The diet of toothfish species Dissostichus eleginoides and Dissostichus mawsoni with overlapping distributions

Authors

  • J. Roberts,

    Corresponding author
    1. Division of Biology, Imperial College London, Silwood Park Campus, Buckhurst Road, Ascot, Berkshire SL5 7PY, U.K.
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  • J. C. Xavier,

    1. Institute of Marine Research, Department of Life Sciences, Apart 3046, University of Coimbra, 3001-401 Coimbra, Portugal
    2. British Antarctic Survey, Natural Environment Research Council, High Cross, Madingley Road, CB3 0ET Cambridge, U.K.
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  • D. J. Agnew

    1. Division of Biology, Imperial College London, Silwood Park Campus, Buckhurst Road, Ascot, Berkshire SL5 7PY, U.K.
    2. MRAG Ltd, 18 Queen Street, London WIJ 5PN, U.K.
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Tel.: +44 (0) 174 6252079; email: james.o.roberts@imperial.ac.uk

Abstract

The diets of Antarctic toothfish Dissostichus mawsoni and Patagonian toothfish Dissostichus eleginoides were examined around the South Sandwich Islands in the Southern Ocean, one of few regions with overlapping populations of the two species. Despite large differences in the proportion of stomachs containing prey (76·2% of D. mawsoni compared to 7·2% of D. eleginoides), diet composition was broadly similar (Schoener overlap index of 74·4% based on prey mass) with finfishes (particularly macrourids and muraenolepidids) and cephalopods (mainly Kondakovia longimana) comprising >90% of the prey mass of both species. Predation rates of the main fish prey, as mean counts per stomach sampled, were spatially correlated with their relative abundance around the islands derived from fishery by-catch data, suggesting a general lack of prey selectivity. This study supports the view that bathyal Dissostichus are opportunistic carnivores and finds that D. mawsoni and D. eleginoides occupy a similar trophic niche and are likely to compete for prey in regions where both are distributed. The large increase in rate of prey occurrence and size of prey in D. mawsoni stomachs relative to D. eleginoides suggests, however, species differences in feeding behaviour, which may reflect the increased metabolic demands of a cold-water adapted physiology. [Correction added after online publication 13 June 2011: spelling of species name corrected]

Ancillary