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of any kind were quite rare in lowermost Lodore Canyon in 1994-1996, whereas introduced warm water species such as red shiner, sand shiner, fathead minnow, and channel catfish remained common or increased in abundance between 1980 and 1994. Sampling in 2002 to 2004, a period defined mostly by low spring peak flows and low, wane summer base flows, showed that nearly every native fish declined in abundance in Lodore Canyon since 1994 to 1996. More non-native fishes were detected, and many pre-existing ones increased their distribution and abundance. Range and abundance expansions were particularly notable for smallmouth bass, channel catfish, and most small-bodied non-native cyprinids, and reproduction was noted for smallmouth bass, bluegill, black bullhead, creek chub, and brook stickleback for the first time. Abundance of salmonids apparently did not decline appreciably or permanently during the period when relatively warm base flows were present. Changes in the Lodore Canyon fish communityfrom sampling conducted in three periods, 1978 to 1980, 1994 to 1996, and 2002 to 2004.-Fish community comparisons from collections made in the 1978 to 1980, 1994 to 1996, and 2002 to 2004 periods showed establishment of abundant non-native fish species over time and subsequent reductions in the once dominant native fish community (Table 11). At the upper Lodore Canyon site, collections in 1978-1980 revealed the presence of six native fishes, 10 introduced taxa, and one hybrid. Collections made in 1994 to 1996 documented the presence of six native fishes, nine introduced taxa, and three hybrids. Only four native taxa, mountain whitefish, speckled dace, flannelmouth sucker, and bluehead sucker, were found in both periods. Small numbers of roundtail chub and mountain sucker were present in early collections, but were absent in later ones. Colorado pikeminnow, mottled sculpin, and bluehead X flannelmouth sucker were collected in the later period but not in the earlier one. Seven introduced taxa and one hybrid sucker were common to each period. The 1978 to 1980 collections documented the presence of Utah chub and red shiner, which were not collected in 1994-1996. The 2002 to 2004 sampling documented presence of introduced green sunfish and one additional hybrid, taxa not collected in the 1978-1980 period. Sampling in 2002 to 2004 at the upper Lodore Canyon site, revealed the presence of seven native fishes (added roundtail chub compared to 1994 to 1996), 12 introduced fishes (added red 63