[MARMAM] New publication - passive acoustic detection of dolphins at low densities

Will Rayment will.rayment at otago.ac.nz
Tue Sep 20 14:47:42 PDT 2011

The following article concerning passive acoustic detection of Maui's 
dolphins has recently been published. PDFs are available from 
will.rayment at otago.ac.nz

Rayment W, Dawson S, Scali S and Slooten E. 2011. *Listening for a 
needle in a haystack: passive acoustic detection of dolphins at very low 
densities*. Endangered Species Research 14: 149-156.

ABSTRACT: Passive acoustic surveys have potential for detecting trends 
in abundance and habitat use by rare cetaceans. We deployed commercially 
available acoustic data loggers (T-PODs) in 4 harbours on the west coast 
of New Zealand's North Island between 2005 and 2008 to investigate the 
distribution of Maui's dolphin /Cephalorhynchus hectori maui/ and assess 
whether current protection measures are sufficient. A set of decision 
rules was developed to minimise the potential for false positive 
detections. Over 3211 'T-POD days' of acoustic monitoring, 39 click 
trains which satisfied all of our decision rules were detected, 
indicating the presence of Maui's dolphins in Manukau and Kaipara 
Harbours. Data from the site with the most detections were fitted to 3 
models, showing that the number of detections varied temporally (p < 
0.001). The models were also used to show to what degree dolphins could 
have been present at monitored locations yet remain undetected. The 
study highlighted the challenges of passive acoustic monitoring of rare 
species, particularly of small delphinids in an environment which is 
both physically and acoustically challenging. Nonetheless, we 
demonstrated that T-PODs are effective in studies of Maui's dolphin 
distribution, that Maui's dolphins are found in North Island harbours 
and remain at risk from gillnet bycatch. We make a number of 
recommendations concerning acoustic monitoring studies of rare 
cetaceans, principally that a thorough understanding of the target 
signals and the acoustic environment being monitored is essential for 
maximising acoustic detection rates.

The following articles using T-PODs with Hector's dolphins are also 
available as PDFs:

Rayment W, Dawson S and Slooten E. 2009. *Trialling an automated passive 
acoustic detector (T-POD) with Hector's dolphins (/Cephalorhynchus 
hectori/)*. Journal of the Marine Biological Association of the UK 89: 

Rayment W, Dawson S and Slooten E. 2010. *Use of T-PODs for acoustic 
monitoring of /Cephalorhynchus/ dolphins: a case study with Hector's 
dolphins in a marine protected area*. Endangered Species Research 10: 

Will Rayment
FRST Post-doctoral Research Fellow
Marine Mammal Research Group
Marine Science Department
University of Otago
PO Box 56
New Zealand

phone: +64 3 4798304 (w)  +64 21 488961 (mob.)

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