Building a Cetacean Passive Acoustic Network in Belgian marine waters
Added on 2016-09-13
Harbour porpoises and dolphins are often seen in the Belgian part of the North Sea. Because these animals do not easy show, it is quite difficult for scientists to estimate their numbers and distribution. Currently the VLIZ is developing – within the framework of the LifeWatch project – a network of acoustic receivers, able to detect the echolocation sounds produced by harbour porpoises and dolphins. After some number crunching one is able to infer the species present in our marine waters and in the longer term describe some trends.
Left: a C-POD anchored to a shipwreck. Photo: VLIZ. Right: Harbour porpoises (Phocoena phocoena) are often spotted in Belgian marine waters. Photo: Kustfotografie.be/Misjel Decleer.
Harbour porpoises and dolphins (belonging to the toothed whales or Odontoceti) use echolocation to extract information from their surroundings. Dolphins produce clicks in a wide frequency range and are typically short and loud, while harbor porpoises are producing rather longer, but weaker clicks in a narrow frequency range (120 - 145 kHz, mode 132 kHz).
These clicks can be recorded by the passive acoustic device, C-POD (Chelonia Limited), when a marine mammal is swimming in the vicinity of the recorder. The C-POD can record clicks between 20 and 160 kHz including ambient background noise, sonar and other biotic underwater sound. The key to the performance of the C-POD is detection and classification of series of clicks, so-called click trains. Click trains have distinctive features which are used by the classification algorithms to identify the occurring cetacean species.
Currently (August 2016) eight C-PODs are attached to buoys, anchored to ship wrecks or to artificial hard structures positioned along an east-west gradient covering coastal, midshore and offshore zones of the Belgian part of the North sea.
More information: Elisabeth Debusschere, VLIZ (firstname.lastname@example.org or +32-(0)59-34 01 81)