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the most common species collected, representing 98% of the assemblage; numerically, native fishes were 3% of those captured. In the Island-Rainbow Park (IRP) reach of the Green River in the period 1994 to 1996, seven native and 11 introduced species and two hybrids were captured by seining. Non-native taxa represented 98.2% of all fishes captured; most were tolerant of warm water. Red shiner was the numerically dominant species and, when combined with fathead minnow, sand shiner, redside shiner, and flannelmouth sucker, comprised 97 % of the fish community. Relatively unusual captures included a single juvenile Colorado pikeminnow, about 150 mm TL, a juvenile northern pike (112-mm TL), largemouth bass Micropterus salmoides, and green sunfish. In the IRP reach of the Green River in the 2002 to 2004 period, seven native and 12 introduced species and two hybrids were captured by seining. Red shiner, sand shiner, fathead minnow, flannelmouth sucker, and white sucker were the most common species collected, representing 96% of the assemblage; numerically, native fishes were 4% of those captured. Both age-0 and age 1+ Colorado pikeminnow were captured in backwaters. Similar to electrofishing samples, the longitudinal pattern of increasing downstream species richness in seine samples was due mostly to addition of more warm-water tolerant species in a downstream direction as a few cold-water or cool-water species dropped out. Dramatic declines in native fish abundance were noted in nearly every reach between the periods 1994 to 1996 and 2002 to 2004. In Browns Park, native fish composition declined from 33% to 21% and over all Lodore Canyon reaches, percent native fish in seine samples declined from 69% in the 1994 to 1996 period to 14% in the 2002 to 2004 period. Increased abundance of red shiner, sand shiner, and fathead minnow and reduced abundance of speckled dace and native suckers were mainly responsible for changes in fish community composition. Proportion of native fish in samples downstream of Lodore Canyon was low. Spatial and temporal patterns of distribution, abundance, and size-structure of selected species, comparison of 1994 to 1996 and 2002 to 2004 periods.-This section presents overall patterns of distribution, abundance, and size structure for selected species and examines changes 26