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EXECUTIVE SUMMARY The U.S. Bureau of Reclamation, U.S. Geological Survey (Grand Canyon Monitoring and Research Center) and the National Park Service identified a conservation action to relocate approximately 300, 50-100 mm humpback chub to upstream areas of the Little Colorado River (LCR) to offset the potential impacts on humpback chub from proposed mainstem activities. This action was a result of the December 6, 2002 Biological Opinion on the proposed experimental releases from Glen Canyon Dam and removal of nonnative fish. It was hoped that this translocation would increase humpback chub recruitment to adulthood by allowing them an opportunity to exploit the abundant food resources, warm water temperatures, and reduced competition/predation by fewer large-bodied fishes associated with this area. If this experiment is successful, it will supply a viable action to expand humpback chub distribution within the LCR and provide additional security while other successful recovery actions are being implemented in the Colorado River or one of its tributaries. We completed reconnaissance surveys to collect baseline ichthyofauna and water quality data above Chute Falls in June 2003. Speckled dace was the dominant species captured and small numbers of common carp, fathead minnow, black bullhead, red shiner and green sunfish were also found. In addition, several rainbow trout were also seen but avoided capture. Water quality parameters, particularly C02 levels, were consistent with previous studies and increased upstream toward Blue Springs. In August 2003, the U.S. Fish and Wildlife Services Arizona Fishery Resources Office (AZFRO), along with personnel from the Arizona Game and Fish Department (AGFD), released 283 humpback chub into the Little Colorado River, above Chute Falls, near river kilometer (RKM) 16.2. Humpback chub were captured via baited hoop nets and seining in the LCR near the confluence of the Colorado River. All translocated fish were implanted with a yellow elastomer tag near the dorsal fin insertion on the left side to identify them from downstream populations. Fish were transported upstream via helicopter and were on 3 liters/minute of oxygen during transport. Due to high C02 levels above Chute Falls (220 mg/L) as compared to downstream areas (83 mg/L), it took nearly 5 hours to temper the humpback chub to the water conditions above Chute Falls. After tempering, fish were transferred to live cars in the river and monitored for an additional 17 hours before release. Fish were observed feeding and dispersing into downstream habitats in search of cover post-release. In October 2003, AZFRO, along with personnel from AGFD initiated monitoring to detect translocated humpback chub above Chute Falls. A total of 42 humpback chub were captured over three days in baited hoopnets deployed from RKM 14.5 to 16.8. Significant fading of the elastomer tag occurred in nearly all humpback chub captured and 9 of 42 had no visible tag. One of the larger individuals, 143 mm, was found 0.5 RKM upstream of the release site and had no visible tag. This suggests either upstream movement from below Chute Falls or significant growth and subsequent loss of the elastomer tag. The largest marked individual was 134 mm, which indicates that this fish experienced at least 34 mm of 2