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INTRODUCTION Altered flow, sediment, and temperature regimes in regulated rivers have been implicated as factors responsible for reduced distribution and abundance of native aquatic biota (Pelts 1984, Ward 1989, Ward and Stanford 1995, Stanford et al. 1996, Poff et al. 1997). In snow-melt dominated streams in western USA, dams reduce spring discharge maxima, which disrupts channel-flood plain interactions and channel forming processes. Deep-releases from reservoirs reduce spring and summer water temperature downstream from dams and cause shifts in composition of fish and invertebrate communities from warm stenothermic native species to non-indigenous cold-tolerant eurytherms (Holden 1979, Ward and Stanford 1979, Stanford et al. 1996). Remnant populations of native fishes may persist as long-lived adults, but reproduction is often reduced or eliminated by cold spring and summer water temperatures and other effects of regulation. Non-indigenous species that spread from reservoirs or tailwaters are another mechanism for reduction of native species. Such reductions may manifest through negative effects of predation, competition, or introduction of diseases and parasites and may be especially problematic in western USA systems because indigenous communities have naturally low diversity and may be susceptible to invasion (Minckley and Deacon 1968, Stanford and Ward 1986, Moyle et al. 1986, Carlson and Muth 1989, Minckley and Deacon 1991, Olden et al. In press). Protocols for river restoration promote re-establishment of natural physical processes in streams with hypothesized benefits for native biota, including fishes (Stanford et al. 1996, Poff et al. 1997). Re-establishment of annual flow maxima to maintain channel geomorphology and flood plain connectedness, reduction of baseflow fluctuations to enhance stability and food web functioning of low velocity nearshore areas, and restoration of more natural seasonal temperature patterns are examples of key processes that may facilitate recovery of native biota (Stanford et al. 1996). However, tests of river restoration hypotheses are few (but see Propst and Gido 2004). 1