Passive Acoustic Monitoring (PAM) (www.passiveacousticmonitoring.co.uk) of marine mammals and their activity has become a critical element during oil, gas, seismic, wind farm and other offshore operations. Ocean Science Consulting Ltd (OSC), established in 2004, were the first in the world to use acoustic techniques to monitor harbour porpoises (Phocoena phocoena) feeding in proximity to oil and gas platforms in the North Sea (www.osc.co.uk). These studies were carried out with the use of T-POD porpoise click detectors. To this day, OSC has employed the use of T-POD Passive Acoustic Monitoring systems to gather data on harbour porpoises and other odontocetes (toothed whales, dolphins and porpoises) using bio-sonar (echolocation) click train detection, providing valuable temporal (time) information on presence and habitat usage.
T-POD features & design
The T-POD click detector offers an economical solution to gathering high volumes of data whilst negating the need for substantial levels of field-work. These Passive Acoustic Monitoring systems log frequency, duration and bandwidth of each porpoise click, as well as current environmental temperature and attitude, while filtering-out unrelated external noise simultaneously. The T-POD porpoise click detector is designed to record clicks between 9 kHz and 170 kHz, ensuring only porpoise click trains, which fall inside this range, are logged, further reducing audio contamination.
Being relatively inexpensive, T-PODs simply comprise an omni-directional hydrophone, an analogue processor and a timing/logging system. Logged data are then run through dedicated analysis software on a PC which identifies and classifies click trains.
In a T-POD click detector study on Hector’s dolphins (Cephalorhynchus hectori) with over 56 hours of observations comprising over 2000 individual clicks, acoustic detections were made only when dolphins were confirmed to be present and there were no false detections when there were no animals in the area. Furthermore, in another study 93% of the days with T-POD data had detections, all over varying distances, and could therefore conclude that porpoise click detection rates reflect differences in porpoise density.
Designed and optimised for performing Environmental Impact Assessments (EIAs), the T-POD is a key factor in investigating connections between industrial activities and porpoise behaviour. Studies are carried out most effectively over extended time periods, from a few days up to several years at a time. These porpoise click detector systems were formerly the only devices available commercially that detected porpoise click trains, although they have been superseded recently by the more modern C-POD (www.c-podclickdetector.com), which is also capable of logging click intensity. Despite this, the T-POD porpoise click detector is still used widely as the tried and trusted method of static Passive Acoustic Monitoring (www.t-pod.co.uk).
T-PODs & OSC in the field
Ocean Science Consulting has a commendable track record using T-POD porpoise click detector devices; our unique deployment method and moorings have earned us a 100% recovery rate to date, meaning none of our T-POD or C-POD units have been lost, whereas most marine scientists estimate high percentage loss with each deployment. Combine this admirable record with the T-POD’s famous detection ability and it’s easy to see why OSC are considered pioneers of T-POD odontocete studies in the North Sea.
The T-POD can log harbour porpoise activity accurately up to a range of around 300 m, with a proven reliability of almost 100% within the ranges of 70-100 m. A scientific study concluded that the T-POD click detector displayed almost flawless accuracy from a distance of 198-239 m, as confirmed by visual sightings. Furthermore, lower frequencies, which the majority of odontocetes vocalise at, can be detected accurately at even greater distances up to and even beyond 1500 m for some species. Some scientists have speculated that T-POD click detectors may be capable of identifying marine mammals at far greater distances than believed previously. For detection of deep-diving species, such as pilot whales (Globicephala spp.) and various beaked whale species, C-POD units are also available in deep-water versions.
Dedicated service through OSC
Ocean Science Consulting are dedicated to providing the best possible service in porpoise detection and study, and our team of marine scientists are proven experts in T-POD and C-POD application. Visit our main site; www.osc.co.uk for more information and support.