Radios in Fish

Hundreds of spawning salmon are being tracked by radio receivers along the Columbia River. They were pulled out of the water and a three-inch-long plastic capsule containing a miniaturized, battery-powered transmitter was put down the throat of each. After being put back into the water they are tracked by radio receivers. Each transmitter gives out its own beep code. By means of the transmitters scientists determine the navigational routes of the spawning fish.