Acoustic Tags are attached to animals and they transmit a sound signal that sends information about the tagged animal to a receiving instrument. This provides data on characteristics such as depth, temperature, and amount of light in the surrounding water. A hydrophone receiver picks up the sound signal and converts it to data that researchers can use. It is somewhat limited in range, since the receiver needs to be within range of the transmitted signal. For more extensive study of large-scale fish movement, scientists use a series of receivers permanently placed underwater to pick up the acoustic signal sent by tagged animals of many species as they travel within range of the receivers.
Click on the link below to see what Census projects use this technology: