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basis. Two electrofishing sampling trips were made each year from 2002 to 2006, one in mid to late July and one in mid to late September. Inflatable raft-based Smith-Root electrofishers were employed. Water conductivity was 300 to 700 microsiemens and electrofishing units usually produced 3-6 amperes with about 350 volts. Generally, 1.5 to 3 km reaches were electrofished before fish were identified, and lengths and weights taken on about every other sample. Electrofishing effort was continuous throughout the reach and concentrated along river banks, in deep pools, riffles, eddies, or near cover. We attempted to capture all fishes that were stunned. Electrofishing samples collected in 2002 in summer (both rafts) and autumn (one raft) were potentially biased downward compared to samples collected in 2003 to 2006 because the anode and cathode plugs were switched. This caused the relatively small surface area dropper sphere in the front of the raft to become the cathode and the relatively large surface area cables positioned mid-raft to become the anodes. The result was fewer fish were attracted to the anode and sometimes came up at the side of the raft rather than the front, which resulted in less efficient sampling. However, mean capture rate of all species combined over the study period was only slightly higher when the 2002 data was excluded (2.65 fish/h average per all species, 95% CI = 2.43 to 2.89, compared to 2.42 fish/h, 95% CI = 2.24 to 2.61 with 2002 data included). Also, of nine species most often captured by electrofishing, five increased in mean abundance when 2002 data were excluded and four decreased. Since inclusion of that data appeared to have little effect on overall abundance values, we retained 2002 data in all analyses. Trammel net sampling was mostly confined to Whirlpool Canyon, because that reach contained deep eddy habitat most likely to support humpback chub. A few trammel net samples were collected in Mitten Park and Lodore Canyon. Multi-filament trammel nets (23 m long x 1.8 m deep; 25-cm outer mesh, 2.5-cm inner mesh) were set in late summer or autumn when water temperatures were relatively low so that fish mortality would be minimized. In autumn 2003 we conducted three consecutive sampling trips (passes) in an attempt to obtain an abundance estimate for chubs in Whirlpool Canyon, but sampling of that intensity was not conducted in other years. The main sampling sites for trammel nets were in upper Whirlpool Canyon just upstream and downstream of Rain Camp (river kilometer (RK) 550.8), at a large 10