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MEPS
Marine Ecology Progress Series

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MEPS 478:301-302 (2013)  -  DOI: https://doi.org/10.3354/meps10337

COMMENT
Pseudo-replication confounds the assessment of long-distance detection of gillnets by porpoises: Comment on Nielsen et al. (2012)

Stephen M. Dawson1,*, David M. Lusseau2

1Marine Science Department, University of Otago, PO Box 56, Dunedin, New Zealand
2Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, AB24 2TZ, UK

ABSTRACT: The harbour porpoise Phocoena phocoena is one of the small cetacean species most frequently caught in gillnets. Understanding how this occurs is important to devising effective mitigation strategies. To assess the distance at which harbour porpoises can detect and avoid gillnets, Nielsen et al. (2012; Mar Ecol Prog Ser 453:241-248) quantified the movement of porpoises through a study area when a gillnet was present, and when it was not. They claimed to provide evidence that porpoises detected gillnets at distances >80 m, much farther than was thought possible. We show, however, that their results are undermined by pseudo-replication, and hence that their conclusion is unreliable. Mixed-effects modelling (van de Pol & Wright 2009; Anim Behav 77:753-758) can be used to avoid this problem.


KEY WORDS: Harbour porpoise · Echolocation · Gillnet · Pseudo-replication


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Cite this article as: Dawson SM, Lusseau DM (2013) Pseudo-replication confounds the assessment of long-distance detection of gillnets by porpoises: Comment on Nielsen et al. (2012). Mar Ecol Prog Ser 478:301-302. https://doi.org/10.3354/meps10337

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