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already been discussed. Roundtail chub were rare in this reach and reproduction, while detected, was limited. Additional non-native fishes collected in the Green River upstream of the Yampa River in 2002 to 2004 included brook stickleback Culea inconstans, bluegill Lepomis macrochirus, and black bullhead Ameiurus melas. None of these taxa was collected during 1994 to 1996 (black bullhead was captured in 1978-1980). We also noted reproduction by northern pike and smallmouth bass during this time period. Thus, the historical fish community of the Green River upstream of the Yampa River has undergone dramatic shifts in composition, abundance, and reproductive capability at least three times since 1962 in response to dam construction and river regulation. A pre-impoundment fish removal program also likely reduced distribution and abundance of native fishes in the regulated reach; subsequent re-invasion likely did not occur because of cold releases (Holden 1991). Post- penstock re-invasion of the regulated reach and subsequent reproduction by native and non-native fishes demonstrated the powerful role that water temperature played in regulating distribution and community composition. Discharge modifications implemented in 1992, and the thermal enhancement that occurred as a result of it, also appeared to further shift the fish community and habitat in the Lodore Canyon reach of the Green River toward pre-dam conditions, based on 1994 to 1996 sampling (Bestgen and Crist 2000). It should be noted that fish community shifts detected during sampling from 1994 to 1996 may be due to a combination of delayed response of the fish community to thermal modification in 1978 and changes in flow and temperature regimes since 1992 (Bestgen and Crist 2000). Several native taxa including bluehead sucker, flannelmouth sucker, speckled dace, and mountain whitefish remained abundant. Colorado pikeminnow also increased in distribution and abundance in the 1994 to 1996 period compared to earlier ones, which may have been attributable to improved habitat conditions or to increased dispersal of individuals from expanding populations in other portions of the basin in the mid-1990's (Bestgen et al. 2005). Distribution and abundance of cold water rainbow and cutthroat trout have declined since 1980; brown trout, which are more tolerant of warm water, were relatively more abundant. Salmonids 62