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~. RADIOTAG~I~1G RA20RBACK SUCKERS:- GILA RIVER, ARIZONA 1988-1989 Paul C. Marsh and =~. L. Minckley Center ~^r Environmental Studies and Department'of Zooiogy Ar~-ona State University Temae Arizona X5287 13 June 1989 Four wild, adu:t razorback suckers trammel netted 20-23 May 1988-from Lake Mohave. Arizona-Nevada, plus 10, 4-, 6-, or 7-year old, hatchery- prooagated (Wexler NFH, New Mexico) F1 fish (Appendix 1) received surgically-implanted, internal. radio tags on 24 May 1988. Fish were released after surgery-into the Gila. River at the Old Safford Bridge, Gr=enlee Co., Arizona, and .tracking began immediately thereafter. All fish were located within 0.8 km of the release site during the 12 hr following stocking. As of mid-July 1989 C32 d after release), two fish with functional transmitters remained alive. eight others died and their transmitters were recovered, contact was lost with two fish Cno contact after i2 hr), and two fish died and/or released their transmitters, but these last two were not retreived. No contacts with these fish were established during later exercises (below). Three of the original 14 fish moved upstream an average of 7.2 km trange 0.1 to 23.7 km): these remained at large an average of 10 d (range 1 to 32 d). Eleven fish moved downstream an average of 11.9 km (range 1.6 to 32.0 km) and contact was maintained for 19 d (range 4 to 32). Stream channels occupied by fish (Table 1) averaged 10 + 5 (SD) m wide, 0.4 ± 0.3 m deep, and 0.21 ± 0.17 m/sec current velocity (n = 30). There was significant differences habitats of fish moving up- versus downstream. Individual tracking histories are In Appendix 1. Radio-trackl`ng was further conducted by truck along.128 km of mayor water-delivery canals and drains in the Safford Valley, and throughout the Glla River reach from San Jose diversion dam .downstream to the delta at San Carlos Reservoir. .Confidence was high that radio-implanted fish would be detected because depths are relatively shallow (rarely exceeding 0.5-0.28 m), and equipment was deployed either directly on or In close proximity to the water. However, no contacts were established. Because of high, short-term mortality of fish in May 1988. surgery was performed on a second group of nine, 4-year old hatchery-produced fish under controlled conditions at Dexter NFH. .After radio-implantation on 30 August 1988, fish were placed into an outdoor pond to recover-from traumas associated with handling and surgery. One fish died the following day, and a second a month later: recovered transmitters were successfully implanted by Dexter personnel into healthy fish.