Porpoise Detector
Porpoise Detectors (POD) or Porpoise Click Detectors (German porpoise detectors) are unmanned floating bodies for researching porpoises (Phocoenidae). The devices record the click sounds of the porpoises through acoustic sensors, process and store them. The PODs are usually used to research the habitat use and population size of marine mammals .
technology
PODs are floating bodies, mostly in the form of tubes, which are equipped with sensor technology and work as self-sufficient data loggers . The underwater microphones record the "click" sounds emitted by the marine mammals in the ultrasound range and store them, supplemented by precise time data. In the late 1990s, the PODs were developed to investigate the echolocation behavior of harbor porpoises and other dolphin species in the vicinity of fishing nets, cf. Bycatch .
The sound is first picked up by a hydrophone (oscillations in the frequency range between 20 and 160 kHz) and converted into an electromagnetic signal. This is passed through a downstream bandpass filter into a data processing and storage unit. As a rule, various parameters (frequency, number of cycles, amplitude and envelope ) are saved . In addition, each POD contains a power supply in a watertight, pressure-resistant housing. Noise can be recorded in a preset frequency range of the echolocation sounds of porpoises.
According to the status of 2012, the echolocation or click sounds of a porpoise could be recorded in a radius of up to 100 m away.
The saved data can be downloaded from the recovered device at the end of a measurement cycle (up to ten weeks under favorable conditions). Further processing is carried out using software, some of which has been specially developed for the PODs (e.g. "T-POD.exe" from the manufacturer Chelonia, UK). This includes a search algorithm for specific sound patterns in the data. These are recognized and classified for further evaluation.
Some of the devices are also called C-PODs, with the "C" standing for Cetacean… -POrpoise Detector.
Porpoise Click Logger
Porpoise Click Loggers (PCLs) are special PODs and simultaneously record the sound pressure and the duration of sound events in two frequency bands (60 and 130 kHz). A subsequent analysis that can be specified by the user enables the detection of porpoises. The devices can be used for up to three months and are equipped with a storage capacity of 8 GB (as of 2012) .
Use of PODs
PODs are now used for research in many marine areas around the world. The systems are relatively inexpensive and provide long-term data. Thanks to the autonomous operation, fewer employees are required than with alternative methods, such as the use of a towing microphone or aircraft counting.
PODs in Germany
In recent years, research projects have established T-PODs as measuring devices for passive acoustic investigations into harbor porpoises. The suitability of the devices for detecting the presence of porpoises in an "overheard" area led to their use in a large number of projects.
BfN research on the designation of marine FFH areas
In Germany, the West Coast FTZ and the Stralsund Marine Museum started a POD project in cooperation with the BfN . In the German Baltic Sea, Porpoise detectors (T-PODs) were used to carry out investigations in the exclusive economic zone and in areas close to the coast: in the Kadet Channel and in the Fehmarnbelt . These are particularly important habitats for harbor porpoises in the German Baltic Sea. As a result, it was shown that harbor porpoises are present all year round in the Fehmarnbelt and in the German territory around Fehmarn. Harbor porpoises have also been regularly detected in the Kadetrinne and the neighboring coastal area.
The BfN wrote about the use of the Porpoise detectors: The acoustic monitoring of harbor porpoises with T-PODs has proven to be a very suitable method in the area of the German Baltic Sea for studying habitat use and the distribution of the species.
FTZ west coast
The FTZ West Coast first put T-PODs into operation in the North Sea in 2002.
Maritime Museum Stralsund (MMS)
In 2011, the Maritime Museum Stralsund started the SAMBAH project - Static Acoustic Monitoring of the Baltic Sea Harbor porpoise . All EU countries around the Baltic Sea are participating in this project. The project is financed by the European Union as part of a LIFE + program that has been running since 2010. SAMBAH's most important goal is to support the preservation of the Baltic harbor porpoise population with scientific data. For this purpose, 300 click detectors will be deployed in the Central Baltic Sea for the period from May 2011 to May 2013. They should determine the density, frequency and distribution of the harbor porpoise population. In addition, preferred habitats and areas with a higher risk of conflict due to human activities are to be identified for harbor porpoises. Another research goal was to develop a method to cost-effectively monitor porpoises over a large area.
The MMS uses C-PODs with an operating time of four months. The devices have a storage capacity of 4 GB ( SD card , expandable).
In a second, smaller research project, the MMS has been investigating the comparability of different static passive acoustic monitoring methods since 2010. In the COSAMM project (investigations into the comparability of various static passive acoustic monitoring methods for the detection of porpoises and other toothed whales) all available click detectors for porpoises were compared in order to later make representative and comparable statements about the occurrence of the animals despite the use of different devices to be able to.
Web links
swell
- ↑ http://www.bfn.de/habitatmare/de/downloads/berichte/Schweinswale_PODs_Ostsee_2006.pdf ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. paper from 2006, p. 2
