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from the system and larger-bodied predators examined for stomach contents. Trammel nets, seining, and angling were also attempted, but were abandoned because of high loads of drifting algae (trammel nets), rocky and algal covered bottoms (seining), and the low numbers of large-bodied fish (angling). We recorded visual observations of large-bodied nonnative fishes. Because high levels of dissolved CO2 have been considered a potential deterrent to humpback chub residing in this region (Mattes 1993; Strength 1997), we collected samples at eight separate locations from below Upper Atomizer Falls (13.87 RKM; where humpback chub have been historically captured) to Blue Springs (20.72 RKM). These measurements were taken by titrating LCR water mixed with phenolphthalein indicator with 3.636 N Sodium Hydroxide using a HACH digital titrator (Model 16900-01; Hach Co., Loveland, CO). We used a graduated cylinder to collect water and decant it into disposable clear plastic cups for each individual titration. This was to alleviate problems associated with contamination resulting from residue Sodium Hydroxide and CaCO3 precipitation. We collected at least five samples at each site, whereby the highest and lowest titration was discarded (i.e., greatest outliers) before taking means of the samples. We also measured water temperatures at each site because of its influence on CO2. Water turbidity measurements (mean nephelometric turbidity units "NTU", Hach Model 2100P Turbidimeter, Loveland, CO) were taken daily at 14.7 RKM. Only one potential helicopter landing site located at 16.2 RKM was considered suitable during flood conditions (Figure 1). Although numerous sandy beaches were available, they: could easily become inundated under higher flows. A comparison between our map with that of Robinson et al. (1996) revealed that they had previously used this site (i.e., their second lowest site) to examine the survivorship and behaviors of humpback chub in June 1994. This site was ideally located to translocate, acclimate, and release humpback chub within a large vegetated pool. In addition, this area was where Robinson et al. (1996) believed that humpback chub could tolerate the CO2 concentration, and was >2 RKM above Chute Falls. The site also offered personnel high-ground protection from floods. Translocation Trip We conducted the humpback chub translocation trip from July 28 -August 1, 2003. On the first day two biologists flew to Boulder Camp (1.9 RKM) and deployed 14 baited hoopnets between 1.8 to 2.6 RKMs, while the other two biologists flew to the 16.2 RKM release site to construct a helicopter landing pad. We pulled all nets the following day and transported 50 -100 mm humpback chub back to camp, where they were placed in holding nets secured in the LCR, and left undisturbed to digest consumed bait until the following evening (>24 hours post-capture). On July 30, 2003, 300 humpback chub were measured (TL; mm), anaesthetized with tricaine methanesulfonate (MS-222), implanted with yellow elastomer tags near their dorsal fins on the left side (for later verification purposes), and allowed to recover overnight in an aerated transport tank. On July 31, 2003 the transport tank was set to deliver 3 liters/minute oxygen and slung by helicopter to the 16.2 RKM release site. At the release site, we slowly tempered the humpback chub by exchanging 1 /3 of the oxygenated holding-tank water with fresh LCR water every 15 minutes until CO2 7