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

• Published in: Journal of the Marine Biological Association of the United Kingdom
• Main Authors: Kyhn, Line A., Tougaard, Jakob, Teilmann, Jonas, Wahlberg, Magnus, Jørgensen, Poul B., Bech, Nikolaj I.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 2008
• Subjects: Harbour porpoise; Phocoena phocoena
• Online Access: http://dx.doi.org/10.1017/s0025315408000416; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0025315408000416

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.