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<br />.. Dispersal of stocked bonytails was predominantly downstream. Both recaptures of <br />stocked juvenile bonytail and telemetry data for adult bonytail demonstrated that fish may <br />move downstream relatively large distances (up to 120 river miles), but remained within <br />the flat-water reaches in which they were released. <br /> <br />.. Longitudinal overlap between bonytail and other Gila species was relatively low in the <br />Colorado and Green rivers. In the Colorado River, the vast majority of other Gila species <br />were centered near the Dolores River. The results for the Colorado River may be biased <br />due to the propensity to sample the area close to the release site more intensively. In the <br />Green River, longitudinal overlap was higher. However, the largest concentrations of <br />other Gila species were found above the release site in Gray Canyon and in the area within <br />20 river miles below the release site (RM 120). <br /> <br />.. Electrofishing was the most efficient method for monitoring stocked bonytail in regard to <br />river miles covered, habitats sampled, and man hours required. <br /> <br />RECOMMENDATIONS <br /> <br />.. Stock hatchery-reared bonytail in the Colorado and Green rivers at a mean target size of <br />300 mm. with additional assessment of bonytail stocked in the 200 mm size range. A lack <br />offish stocked at sizes between 150-300 mm made assessment of size to survivorship <br />relationships difficult and restricted our recommendations to stocking bonytail at 300 mm. <br />Although monitoring efforts for razorback sucker stocking in the upper basin (Burdick <br />2002; Ryden 2001) and our limited results with bonytail suggest that stocked fish >300 <br />mm show greater probability of survival, stocking bonytail in the 200 mm size range <br />should also occur to allow for assessment of optimal release size. <br /> <br />.. Mark all hatchery-reared bonytail with PIT tags prior to release. <br /> <br />.. Stock 300 mm bonytail in March to early April to allow for an adequate acclimation <br />period. At fish densities reported for 1999-2001 in the Wahweap State Hatchery this <br />would entail maintaining the fish for three full growing seasons and releasing them the <br />following spring. <br /> <br />.. Monitor stocked bonytail in mid-April through May. Electrofishing should be used as the <br />primary monitoring method. Monitoring should be intensive, covering the entire flat-water <br />reaches in which bonytail are stocked. Electrofishing should be continuous along both <br />shorelines and within all accessible habitats. Ideally, three passes should be completed in <br />the spring each year allowing for annual point population estimates. The Colorado <br />pikeminnow population estimates occurring in 2003 and again 2006-2008 on the lower <br />Green River and in 2003-2005 on the Colorado River could be utilized as annual <br />monitoring efforts. By monitoring at this time, we will be able to examine both short-term <br />condition of the recently stocked cohorts as well as determine overwinter and long-tenn <br />survival and dispersal for previously stocked cohorts. <br /> <br />19 <br />