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2 I I I I I I , I I I I J ~..:-.-I. -- ~. 1 J.-~.. . ~ I I ....'..1 -. ~, I METHODS Sources of Fish Lake Powell Approximately 300 razorback suckers were transported from Ouray National Fish Hatchery, Utah, to golf course ponds in Page, Arizona, on May 16, 1996. Fish originated from "Green River" stock in 1993 and were designated "surplus" production from the upper basin stocking augmentation program. Fish were held in golf course ponds to determine the ponds suitability as grow-out facilities (Mueller and Wick 1997). Fish were scheduled to be released into critical habitat areas of Lake Powell (USDOI 1996a & 1996b). Thirty fish averaging 358 mm in length (335-402 mm) were captured from the golf course ponds on May 3, 1997 (Appendix A). Fish were treated with stress reducing chemicals (salt, MS-222, stress coat, and furacin) and transported by boat to Castle Creek Canyon, River Kilometer (RK) 72 on the San Juan Arm of Lake Powell. Lake Mohave Lake Mohave were supplied by the Willow Beach National Fish Hatchery. Fish were smaller, averaging 241 mm (201-290 mm, Appendix A). Fish were hauled in a tank treated with stress reducing chemicals. In addition to sonic transmitters, the fish were also PIT (passive integrated transponder) tagged. Telemetry Equipment and Survey Techniques Ultrasonic transmitters were chosen over radio transmitters for their ability to be detectable regardless of depth, which in Lake Powell could exceed 100 m. Transmitters have been successfully used on both small razorbacks suckers and bonytail (Gila eZegans) in Lake Mohave (Marsh et al. 1996, Mueller et ale 1998). Transmitters (Sonotronics, model MT-95-2) used for this study measured 9x36 mm, weighed 3 g in water, and had an estimated battery life of90 days. Normal detection range was 500 m. Previous attempts to surgically implant sonic transmitters in juvenile razorback suckers led to high transmitter shedding and possibly mortality (Ryden 1997b, Mueller et al. 1998). We wanted to test external attachment techniques that might reduce stress, increase survival, and would eventually be shed. A literature review revealed various methods of attaching transmitters. Saddle-mounted transmitters were tested on several surrogate species (white suckers [Catostomus commersoni] and largemouth bass [Micropterus saZmoides]) without much success (Winter et al. 1978) due to severe fungal and bacterial infections at the point of contact. Various combinations of metal wire harn~sses were tested to determine if galvanistic corrosion could be used as a release mechanism. Combinations of steel, aluminum, and copper proved unreliable.