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47 IS RADIO-TAGGING A VIABLE TECHNIQUE FOR COLORADO SQUAWFISH? Douglas Selby, BIO/WEST, Inc. A study to determine the spawning requirements of the endangered Colorado Squawfish (Ptychocheilus lucius) was begun in April 1978 under a contract from the Western Energy and Land Use Team of the U.S. Fish and Wildlife Service. The project made use of radio tags surgically implanted in the fish, a technique frequently used on salmon, but never on Colorado squawfish and only once previously in the Colorado drainage. Transmitters, receivers, and antennas used were all manufactured by Smith-Root Corporation. The transmitters operated on the 40.600 Mhz band. Transmitters were implanted in seven squaw- fish, all of which seemed to be little affected by the surgical procedure. All but one of the seven fish were lost within a week and Never relocated despite intensive searches. The one fish which was tracked moved a total of 89 miles downriver from its point of release in a period of six weeks. He was frequently monitored during this time and all indications were that he was healthy and behaving normally. The problem in locating the other fish apparently was the result of weak transmitters. After thorough searches for the lost fish with negative results, 5 unimplanted transmitters were tested under field conditions and found to be much weaker than advertised. In 2 feet of water, all of the transmitters had ranges of under 100 yards and 2 had ranges of under 100 feet. The transmitters also lost strength with extended operation. Because the transmitters were the obvious cause of the failure of the project, we have recommended a second attempt to determine spawning requirements of squawfish using new pretested transmitters. The successful tracking of one fish for 6 weeks indicates the research potential of radio tagging other native species in the Green River.