New Zealand Journal of Marine and Freshwater Research abstracts

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Short communication

Observations of Hector’s dolphins (Cephalorhynchus hectori) associating with inshore fishing trawlers at Banks Peninsula, New Zealand

William Rayment^1,2

Trudi Webster^1,2

¹Department of Marine Science

²Department of Zoology

University of Otago

P.O. Box 56

Dunedin, New Zealand

email: will.rayment@xtra.co.nz

Abstract Fishing activities have the potential to alter the behaviour of cetaceans and pose a threat through bycatch. We present observations concerning the influence of inshore trawling on group size and behaviour of Hector’s dolphins (Cephalorhynchus hectori) at Banks Peninsula, New Zealand, made during photo-ID surveys from 2003 to 2007. Aggregations of dolphins, typically involved in what we assumed to be foraging behaviour, were observed following small inshore trawlers year-round. Group size was larger for aggregations of dolphins following trawlers (mean ± SE = 22.9 ± 1.3, n = 83) than for non-trawler groups (3.7 ± 0.2, n = 439), and dolphins were typically in a more “excited” state, frequently exhibiting aerial and sexual behaviours. We suggest that trawlers increase the availability of prey for Hector’s dolphins and hence foraging behind trawlers is an energetically favourable activity. However, following trawlers probably also increases the risk of being caught in trawl nets, compounding the threats faced by this endangered species.

Keywords trawling; behaviour; bycatch; marine mammal; endangered

 

New Zealand Journal of Marine and Freshwater Research, 2009, Vol. 43: 911–916

0028–8330/09/4304–0916 © The Royal Society of New Zealand 2009

M09018; Online publication date 17 July 2009

Received 1 May 2009; accepted 2 June 2009

PDF file of entire paper: Print-quality (517K) | screen-quality (246K)

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