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have observed some effects. Cowdell and Valdez (1994) found localized hemorrhaging along the spine in 5% of 40 roundtail chub; Muth and Rupert (1996) did not observe any extemal injury when adult razorback sucker were exposed to 60-Hz current in the laboratory, but X-rays showed hemorrhaging along the spine and vertebral damage. Repeated electrofishing should be used only with great care. We failed to capture any humpback chub and only a few roundtail chub in hoop nets. Trammel nets were discontinued in 1986 because of lack of success and trauma to the fish (Karp and Tyus 1990). However, other humpback chub populations have been effectively sampled with trammel nets and hoop nets. In the Grand Canyon humpback chub were captured successfully with hoop nets and trammel nets (Douglas and Marsh 1996), and in Black Rocks (McAda et al. 1994), Westwater (Chart and Lentsch 1999), and Desolation/Gray canyons they were caught successfully with trammel nets. The lack of success in Yampa Canyon is the result of lower fish densities and lack of suitable areas to use trammel nets. The other canyon areas have higher fish densities in fewer locations. For example, at the confluence of the Colorado and Little Colorado rivers in the Grand Canyon, fish occupy about 20 km but 72% are within an 8-km reach (Valdez and RyeI1995), and in Westwater Canyon most humpback chub occur at three locations within 6 km. Although in Yampa Canyon humpback chub are concentrated in certain well known locations, like Irvings Hole, Big Joe, Little Joe, and Five Springs, they are more dispersed through 52 km of river than other populations. In addition, Yampa Canyon does not have the large, deep, stable eddy habitats that make for good trammel netting. Juvenile captures. Seining shallow shorelines, pools, backwaters, and eddies was 13