As part of the Belgian LifeWatch observatory, a permanent Cetacean passive acoustic network is established in the Belgian Part of the North Sea. The sensor network uses C-PODs (Chelonia Limited) to register the presence of harbour porpoise (Phocoena phocoena) in the neighbourhood, as part of the C-POD moorings, acoustic telemetry receivers are also deployed. This acoustic telemetry receivers are both Innovasea and ThelmaBiotel recivers (mainly) and are completelly Open Protocol (OP) enabled. They listen for tagged fish at 69kHz