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Harbour porpoise (Phocoena phocoena) static acoustic monitoring: laboratory detection thresholds of T-PODs are reflected in field sensitivity

Published online by Cambridge University Press:  17 March 2008

Line A. Kyhn ,
Jakob Tougaard ,
Jonas Teilmann ,
Magnus Wahlberg ,
Poul B. Jørgensen  and
Nikolaj I. Bech
Line A. Kyhn*
Affiliation:
National Environmental Research Institute, Frederiksborgvej 399, DK-4000 Roskilde, Denmark Aarhus University, Department of Zoophysiology, C.F. Møllers Allé Building 1131, DK-8000 Aarhus, Denmark
Jakob Tougaard
Affiliation:
National Environmental Research Institute, Frederiksborgvej 399, DK-4000 Roskilde, Denmark
Jonas Teilmann
Affiliation:
National Environmental Research Institute, Frederiksborgvej 399, DK-4000 Roskilde, Denmark
Magnus Wahlberg
Affiliation:
Aarhus University, Department of Zoophysiology, C.F. Møllers Allé Building 1131, DK-8000 Aarhus, Denmark
Poul B. Jørgensen
Affiliation:
National Environmental Research Institute, Frederiksborgvej 399, DK-4000 Roskilde, Denmark
Nikolaj I. Bech
Affiliation:
National Environmental Research Institute, Frederiksborgvej 399, DK-4000 Roskilde, Denmark
*
Correspondence should be addressed to: Line A. KyhnNational Environmental Research InstituteFrederiksborgvej 399 DK-4000 RoskildeDenmark email: lky@dmu.dk
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Abstract

The T-POD (Timing POrpoise Detector) is a self-contained acoustic data logger used for detecting and monitoring the presence of echolocation clicks of small cetaceans. It has become a standard tool in environmental impact assessments and monitoring programmes. Yet, little is known about the variability in sensitivity and detection range of T-PODs. In this study the field performance of ten v3 T-PODs was compared to detection thresholds measured in a tank. The T-POD thresholds ranged from 123 to 132 dB re 1μPa (pp). The detection thresholds of the ten individual T-PODs were different and the differences increased over time. The more sensitive a T-POD was in the laboratory (i.e. the lower the threshold) the more clicks were recorded by it in the field. Threshold correlated differently to the five analysed T-POD parameters (encounters, encounter duration, waiting time, porpoise positive minutes, clicks per porpoise positive minute). This study demonstrates that individual threshold calibrations of T-PODs are necessary to obtain comparable results when monitoring odontocetes with this tool. Regression equations for relationships between T-POD detection thresholds and study parameters obtained during field trials may allow comparisons of T-PODs with different detection thresholds.

Keywords

passive acoustic monitoringPAMporpoisecephalorhynchus130 kHz clickdata loggersurveyacousticscalibration methodscomparability
Type
Research Article
Information
Journal of the Marine Biological Association of the United Kingdom , Volume 88 , Special Issue 6: Marine Mammals , September 2008 , pp. 1085 - 1091
Copyright
Copyright © Marine Biological Association of the United Kingdom 2008

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