Journal Article

Antarctic ecosystem monitoring: quantifying the response of ecosystem indicators to variability in Antarctic krill

Keith Reid, John P. Croxall, Dirk R. Briggs and Eugene J. Murphy

in ICES Journal of Marine Science

Published on behalf of ICES/CIEM

Volume 62, issue 3, pages 366-373
Published in print January 2005 | ISSN: 1054-3139
Published online January 2005 | e-ISSN: 1095-9289 | DOI: http://dx.doi.org/10.1016/j.icesjms.2004.11.003
Antarctic ecosystem monitoring: quantifying the response of ecosystem indicators to variability in Antarctic krill

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The utility of upper-trophic-level species as ecosystem indicators is determined by our ability to relate changes in indices of their performance to changes at lower trophic levels. Such relationships were assessed using indices of predator performance (response vectors) for four predator species, together with independent ship-based acoustic estimates of abundance of their main prey, Antarctic krill (Euphausia superba), from South Georgia in the South Atlantic Ocean. Out of 32 response vectors investigated, 13 showed a significant non-linear relationship, based on a Holling Type II response, to krill abundance, and just five showed a significant linear relationship. Predator responses reflecting the processes during summer, when prey surveys were undertaken, showed the closest relationship with prey abundance. Distinct relationships existed between the variability of indices and the biological processes they measured. Body mass variables had the lowest variability (CVs <10%), whereas those measuring breeding success showed the greatest variability (CVs >50%). Multivariate indices, produced by combining response vectors from all four predator species into a single combined index, provided a better fit with krill data than any of the individual vectors. Whereas population size parameters for individual species showed no relationship with annual estimates of krill abundance, a combined, multispecies population size index did show a significant response. Understanding the form of the relationship between concurrent indicators of prey abundance and key ecosystem metrics/reference points, such as population size, is crucial to the application of monitoring data to management action.

Keywords: Antarctic; ecosystem monitoring; predator; scale

Journal Article.  5127 words.  Illustrated.

Subjects: Environmental Science ; Marine and Estuarine Biology

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