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Colorado squawfish (TL 508-707 millimeters) and razorback suckers were captured by electrofishing in the Green River. Fish were anesthe- tized with MS222 and surgically implanted with radio.transmitters immedi- ately after capture. Surgical procedure was similar to Bidgood (1980) except for several departures. Sutures were individual (usually five) rather than the continuous suture used by Bidgood and the incision was made laterally, immediately anterior and slightly dorsal to the insertion of the right pelvic fin. Suture knots were coated with "Krazy Glue" (Bill Loudemilk, letter to the U.S. Fish and Wildlife Service, March 27, 1980).. Surgical implantation was completed with AVM fish modules (AVM 1979) dipped in melted beeswax. These transmitters (Sm-1) weighed approximately 11 grams and are of "padlock" shape. The units are powered by a mercury (HG-630) battery and have a theoretical life of about 215 days. The units transmitted in the 40.660-40.700 MHz frequency range. Radio receiver sets used were Smith-Root RF-40 and SR-40 models. The RF type enables the investigator to identify any particular frequency transmitted in the 40 MHz range. The SR receiver is a "search" type and will pick up all emitted frequencies in the range. Omnidirectional and pinpointing type antennas were employed. A Larson-Kulrod whip antenna was used to search for implanted fish. This antenna was mounted on a 7.9-inch (20-centimeter) square steel plate elevated about 13 feet (4 meters) above the water when mounted on a boat, or mounted directly to an airplane wing strut. The loop antenna (direc- tional) was used only to triangulate fish location. This was done by boat or from shore. It was necessary to use aircraft to keep contact with several fish at one time. The most successful aircraft used were helicopters and a Piper Supercub (the Piper airplane was designed for low altitude and slow flight). The aircraft were operated as slow as practicable at low elevation. The radiotelemetry program utilized two different methods for recording information about habitat preferences and movement. Long distance movement was determined by attempting to locate all radio tagged fish on a 1 to 2 day interval. The location of a fish was recorded on a one time basis when encountered. In order to obtain more specific information on movement and habitat preferences, a diel sampling procedure was employed. This sampling procedure consisted of observations made continuously over a 24 hour basis as follows 1. The day was divided into three 8-hour periods and one selected at random. A fish was then observed during this period with depth, velocity, and substrate determinations made every 15 minutes. Habitat measurements were not recorded unless fish were stationary for 30 minutes. 2. After a fish had been monitored for three 8-hour periods, the fish with the next tag number was then selected for study. 0 16