science
Fish, Whales Carry Sensors for Oceanographic Research
By Edward Lundquist Senior Science Advisor Alion Science and Technology
Capt. Edward Lundquist, USN (Ret.), is a senior science advisor for Alion Science and Technology in Washington, D.C. He supports the Navy's Surface Warfare Directorate.
Pacific IOOS Region
As we try to better understand the sea, we find that some of the best sensors can be carried by those creatures that live there. Researchers are attaching transponders and sensors to large "free ranging" fish and marine mammals such as whales, dolphins and sea lions that not only give behavioral clues to where these animals are, and where they migrate and breed, but also provide environmental data about the water they are in. According to Dr. Whitlow Au, a researcher with the University of Hawaii, probes can provide acoustic data, time depth profiles, and trajectory information about the course and speed of the animal. The probes are attached to cetaceans by using suction cups and a pole deployment device. The probes are glued to pinnipeds. Position and data telemetry are transmitted to Argos satellites, and relayed to ground stations for analysis. The main sensors placed on marine mammals are the Digital Acoustic Recording Tag (Dtag) from Woods Hole Oceanographic Institution. (WHOI) and the Bioacoustic
Probe (B-Probe) from Greeneridge Sciences, Au says. Both are 'non-invasive,' in that the sensors do not penetrate the skin of the animal. Both are small enough to fit in your hand. "Both tags or probes measure sound emissions from the tagged animals. Both tags have a depth sensor," Au says. "The Dtag has a three axis accelerometer so that dead reckoning information can be obtained and used to estimate the trajectory of the tagged animal. The B-Probe has a two axis accelerometer. The Dtag has two hydrophones and can sample up to 96 kHz for each hydrophone. B-Probe has a sampling rate of 20 kHz. The B-Probe consumes about a fifth of the power as that of the Dtag and so can be used for longer studies and has been used with pinnipeds and cetaceans. Dtag has been used mainly with echo-locating odontocetes (toothed whales)." The self-contained B-Probe includes a hydrophone, behavioral sensors, digital recorder, data storage, and power supply. Its cylindrical 'torpedo' shape is 3.2 cm in diameter and 19.3 cm long, and is pressure tested to 2000 meters (3000 psi). "The typical package detects temperature and depth and sometimes light levels," says Dr. Kim Holland, another University of Hawaii researcher. Satellites can receive the signal coming from the sensors and relay it to a ground station where the data is collected and analyzed. The Argos program is jointly administered by the National Oceanic and Atmospheric Administration (NOAA) and the French space agency, Centre National d'Etudes Spatiales (CNES). The data collection relay system provides global coverage and platform location to monitor drifting ocean buoys and undersea wildlife. "Most tags are involved with figuring out where the animals are. Of course, this often also gives data concerning physical oceanogJune 2008
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