Further evidence that Antarctic toothfish are important to Weddell seals

Abstract 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...

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Bibliographic Details
Published in:Antarctic Science
Main Authors: Ainley, David G., Cziko, Paul A., Nur, Nadav, Rotella, Jay J., Eastman, Joseph T., Larue, Michelle, Stirling, Ian, Abrams, Peter A.
Format: Article in Journal/Newspaper
Language:English
Published: Cambridge University Press (CUP) 2020
Subjects:
Geology
Ecology, Evolution, Behavior and Systematics
Oceanography
Antarc*
Antarctic
Antarctic Science
Antarctic Toothfish
McMurdo Sound
Ross Sea
Weddell Seals
Online Access:http://dx.doi.org/10.1017/s0954102020000437
https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0954102020000437
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Summary:Abstract 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.

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