Cetaceans, particularly diminutive species like the harbour porpoise (Phocoena phocoena), are notoriously difficult to observe and study in the wild, and ascertaining patterns in terms of habitat usage and behaviour, is problematic using visual methods only, mainly due to weather and daylight constraints. The T-POD and C-POD are static (surface or sub-surface moored), autonomous (unmanned), Passive Acoustic Monitoring (PAM) systems (www.pamsystems.co.uk), also known as echolocation click detectors, which can log cetacean activity 24 hours per day for months at a time, with fewer environmental limitations cf. visual observation methods; therefore, this technology can offer a more cost-effective solution for surveys.

C-POD Functionality

The C-POD is the digital successor to the T-POD (www.t-pod.co.uk), but in summary, this technology comprises a hydrophone, processor, memory, and analysis software. Once deployed, the hydrophone detects echolocation clicks from cetaceans and other sources, characteristics of which are logged and stored, ready for downloading onto a PC equipped with the associated programme. The software identifies potential cetacean echolocation click trains, and then, through the use of a complex algorithm, classifies trains into “quality” categories, depending on the likelihood that the click train was produced by a cetacean. Click trains classified as “high” almost certainly originate from cetaceans, and with decreasing order of certainty, subsequent click trains are categorised as “moderate”, “low”, and “doubtful”. In the latest versions of C-POD software, “species” filters include “Narrow-Band High Frequency” (aka “NBHF”), “other cetaceans”, and “fixed rate/boat sonar”. From these data, habitat usage and behaviour can be assessed and inferred by investigating different click parameters and activity indicators. More complex analyses methods can be performed by Ocean Science Consulting Ltd (OSC), as per the company’s peer-reviewed research available at http://www.osc.co.uk