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11 <br />razorback suckers were frozen and returned to Utah State University <br />for enzyme analysis. Flannelmouth and biuehead suckers were dissected <br />to determine sex and maturity. Razorback suckers were sexed before <br />release using external characteristics described by Gustafson [1975] <br />and other characteristics determined from examination of specimens <br />collected and preserved by previous investigators [Vanicek, 1967; <br />HoZden, 19731. For example, the last ray of the anal fin is curved <br />for mature male razorback suckers while it is straight for mature <br />females. The fish were weighed, measured and scales were removed from <br />a key area located midway between the origin of the dorsal fin and the <br />lateral line. Live razorback suckers and Colorado squawfish were <br />tagged with numbered Floy anchor tags and released near the point of <br />capture. <br />Movement <br />Selected male razorback suckers were tracked using ultrasonic <br />transmitters inserted into the body cavity. These transmitters were <br />cylinders (64 mm long, 16 mm in diameter, weighing 19.3 g) and were <br />operated at 157.5 to 180.5 kz. Each transmitter operated on a separate <br />frequency to aid in identification of individual fish. Tracking <br />equipment consisted of a battery powered multifrequency receiver <br />with headphones and a directional hydrophone. Fish movements were <br />monitored from shore or from a small boat. Effective range was <br />shorter than reported by other investigators [Hasler, et at., 1969; <br />Stasko, HorraZ, and Hasler, 1976; Ziebe ZZ, 1973] and varied from <br />150 m in quiet water to 10 m in turbulent or rapid water. Fish <br />locations were determined by triangulation or by estimating the