The C-POD (www.cpodclickdetector.com) is a passive acoustic monitoring (PAM) tool used worldwide to monitor the presence or absence of marine mammals collectively known as cetaceans (toothed whales, dolphins and porpoises). The C-POD uses digital waveform characterisation to select cetacean sonar (echolocation) clicks and logs the time, centre frequency, sound pressure level, duration and bandwidth of each click, along with a whole host of other features. C-PODs are the digital successor to the T-POD (www.t-pod.co.uk).
Cetacean click classification
Cetaceans use a wide variety of sounds for communication in the form of whistles, pulsed calls and clicks. Odontocetes produce dedicated signals with different source properties suited for communication and echolocation. A number of dolphin species produce broadband, high frequency echolocation clicks for navigation and foraging. Sperm whales (Physeter macrocephalus), which only produce clicks, also have dedicated click types with different source properties for echolocation and communication.
Harbour porpoises (Phocoena phocoena) produce stereotypic acoustic click signals to navigate, orientate, feed and communicate under water. The acoustic patterns of these click signals vary with behaviour. High-frequency click train data can be acquired via C-PODs, and this static acoustic monitoring (SAM) instrument is commonly used to record the presence or absence of harbour porpoises.
C-POD click detection
Echolocation clicks, if identifiable to species, can provide useful data for Passive Acoustic Monitoring (PAM) surveys, as odontocetes produce clicks reliably and frequently. The C-POD can detect cetacean clicks successfully between 20 – 160 kHz at a maximum range of 300 m (in ideal conditions, on-axis) for porpoises and at a much greater distance for dolphins. Alternatively, with expert knowledge, C-PODs can be programmed and set to specifically detect and record the echolocation signals from harbour porpoises only.
Projects using C-PODs
Ocean Science Consulting has used C-PODs to record successfully the echolocation clicks of harbour porpoises around oil and gas installations (ICES PDF), prompting widespread press coverage. Other applications include wind farm before-during and after surveys, interaction of cetaceans with fisheries, and general long-term monitoring. C-PODs have proved to be a powerful method to collect data on presence and seasonal distribution of cetaceans, especially harbour porpoises. C-PODs can be used along with visual (www.marinemammalobserver.com) and acoustic (www.passiveacousticmonitoring.com) surveys during Environmental Impact Assessments (EIAs), when monitoring cetacean population trends, providing information on cetacean behaviour, and for numerous types of industry and research projects.
Ocean Science Consulting Ltd. has been operating since 2004 with clients such as the military, media, academia, government and a range of other industries; oil and gas production (rigs, platforms, offshore support, guard and chase vessels), geophysical (2D/3D/VSP seismic and drilling explorations), hydrographical survey, and pipeline (laying, trenching, rock dumping, side-casting and fall pipe vessels). For more information and a list of clients see our main site www.osc.co.uk.