Below is a press release about the Methods in Ecology and Evolution article ‘Estimating effective detection area of static passive acoustic data loggers from playback experiments with cetacean vocalisations‘ taken from Swansea University.
An examination into the detection of harbour porpoises is helping to give new understanding of effective monitoring of species under threat from anthropogenic activities such as fisheries bycatch and coastal pollution.
In a first study of its kind, Dr Hanna Nuuttila, currently at Swansea University’s College of Science – together with scientists from the German Oceanographic Museum, the University of St Andrews and Bangor University – revealed how playing back porpoise sounds to an acoustic logger can be used to assess the detection area of the device, a metric typically required for effective monitoring and conservation of protected species.
Harbour porpoises are best monitored using underwater acoustic dataloggers, which record the echolocation clicks used for navigation and foraging. This study looked at the most frequently used devices to record these animals and devised an experiment that allowed researchers to determine the range of loggers – something that previously hasn’t been known.
Researchers played back artificial and real recorded harbour porpoise echolocation clicks to a number of recorders at varying distances and sound source levels. This allowed them to estimate the proportion of all the sounds that were captured by the device, and assess how this was affected by distance from the sound source to the recorder.
The maximum distance the recorder could capture porpoise sounds from was 566m. The mean effective detection range (EDR) of a raw signal was calculated at just under 200m though. And the range for sounds that could be classified as porpoises by the inbuilt algorithm was 72m. Each underwater click logger would provide a circular sampling station of 144m diameter, which could be used in subsequent abundance estimations.
Harbour porpoises are one of six species of porpoise and are increasingly under threat from anthropogenic activities, such as fisheries bycatch, noise and coastal pollution. They are protected species and monitoring their presence and distribution is legally required.
Lead author Dr Hanna Nuuttila (SEACAMS2 Scientific Officer at Swansea University’s College of Science) said “Although animals can be recorded using acoustic devices, it can be very difficult to quantify the exact ranges and detection areas for acoustic dataloggers, something which is crucial if acoustic data is to be used to estimate animal abundance.
“This study describes a playback experiment and an analytical method to estimate the effective detection range and area for passive acoustic cetacean click-loggers.”
Read the full article (freely available for a limited time):
Nuuttila H, et al. Estimating effective detection area of static passive acoustic data loggers from playback experiments with cetacean vocalisations. Methods Ecol Evol. 2018;00:1–10. DOI: 10.1111/2041-210X.13097
Ben Donovan, Press Officer, Swansea University, Tel: +44 1792 602 382, Email: firstname.lastname@example.org