Moored passive acoustic detectors (e.g. C-PODs) are widely used to study harbour porpoise Phocoena phocoena distribution and relative abundance, but their use in tidal-stream habitats is complicated by the need for retrievable flow-resistant seabed fixings and the occurrence of flow-induced noise in the resultant data. In this study, we explored the use of a new method aimed at tidal-stream habitats, which are of increasing interest for marine renewable energy generation. Porpoise detectors (C-PODs) were attached to multiple drifters and repeatedly set adrift at a tidal-stream site in western Scotland during May 2010 and August 2011. Porpoise vocalisations were successfully detected under varying tidal conditions during approximately 63 h of drifting. Harbour porpoise distribution, as determined by the drifting detectors, was similar to that found using the traditional, yet more logistically intensive, visual and acoustic boat-based surveys and to an extent that found by moored C-PODs. Drifting detectors also mapped tidally driven spatiotemporal variability in ambient noise levels which could influence porpoise detection. In summary, drifters equipped with passive acoustic detectors offer a new, rapid and inexpensive tool for investigating porpoise occurrence and behaviour in tidal-stream habitats, and should be considered as part of a comprehensive marine mammal monitoring approach of these energetic environments in the context of marine renewable energy development and other industries.
Using Drifting Passive Echolocation Loggers to Study Harbour Porpoises in Tidal-Stream Habitats
Title: Using Drifting Passive Echolocation Loggers to Study Harbour Porpoises in Tidal-Stream Habitats
December 02, 2013
Journal: Endangered Species Research
Wilson, B.; Benjamins, S.; Elliot, J. (2013). Using Drifting Passive Echolocation Loggers to Study Harbour Porpoises in Tidal-Stream Habitats. Endangered Species Research, 22, 125-143.