Because the fish in the upper river near Gibson Dam are relatively small (largest in fall 2004 was 15 inches), we need to use small transmitters. The two different sized transmitters we used weighed just 7.7- and 8.9 grams, or about 0.3 ounces each, yet they send out a radio signal that can be detected with a special receiver up to a mile away! It is amazing what can be packaged in these tiny transmitters. For example, the transmitters implanted in fall 2004 have a delayed start, so they will not turn on until spring 2005. Then, once started, they will only emit a radio signal for 12 hours of each day, then turn off at nighttime. And finally, they are programmed to shut off during the winter months. The purpose of these on/off features is to greatly extend the battery life of the transmitter, which dictates how long we can follow our fish. The smaller transmitters should last about 500 days, while the larger ones are rated to last about 700 days, or nearly two years! Another great feature of these transmitters is that each emits a unique code that allows us to track individual fish. Thus, when we locate a signal we will know exactly which fish it is. There is a lot of technology packed into a very tiny waterproof transmitter!