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Further evidence that Antarctic toothfish are important to Weddell seals

Published online by Cambridge University Press:  01 September 2020

David G. Ainley*
HT Harvey & Associates Ecological Consultants, Los Gatos, CA95032, USA
Paul A. Cziko
Institute of Ecology and Evolution, University of Oregon, Eugene, OR97403, USA
Nadav Nur
Point Blue Conservation Science, Petaluma, CA94954, USA
Jay J. Rotella
Department of Ecology, Montana State University, Bozeman, MT59717, USA
Joseph T. Eastman
Department of Biomedical Sciences, Ohio University, Athens, OH45701, USA
Michelle Larue
Department of Earth Sciences, University of Minnesota, Minneapolis, MN55455, USA School of Earth & Environment, University of Canterbury, Christchurch8041, New Zealand
Ian Stirling
Wildlife Research Division, Department of Environment, ℅ Department of Biological Sciences, University of Alberta, Edmonton, AlbertaT6G 2E9, Canada
Peter A. Abrams
Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, OntarioM5S 3G5, Canada


Antarctic toothfish Dissostichus mawsoni and Weddell seals Leptonychotes weddellii are important mesopredators in the waters of the Antarctic continental shelf. They compete with each other for prey, yet the seals also prey upon toothfish. Such intraguild predation means that prevalence and respective demographic rates may be negatively correlated, but quantification is lacking. Following a review of their natural histories, we initiate an approach to address this deficiency by analysing scientific fishing catch per unit effort (CPUE; 1975–2011 plus sporadic effort to 2018) in conjunction with an annual index of seal abundance in McMurdo Sound, Ross Sea. We correlated annual variation in scientific CPUE to seal numbers over a 43 year period (1975–2018), complementing an earlier study in the same locality showing CPUE to be negatively correlated with spatial proximity to abundant seals. The observed relationship (more seals with lower CPUE, while controlling for annual trends in each) indicates the importance of toothfish as a dietary item to Weddell seals and highlights the probable importance of intra- and inter-specific competition as well as intraguild predation in seal-toothfish dynamics. Ultimately, it may be necessary to supplement fishery management with targeted ecosystem monitoring to prevent the fishery from having adverse effects on dependent species.

Biological Sciences
Copyright © Antarctic Science Ltd 2020

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