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ISMP backwater sampling evaluation habitat variables suggested a positive association with river kilometer, surface area, and maximum depth. The river kilometer attribute suggested that, on average, two more species would occur in the most upstream backwater compared to the most downstream one. The surface area (p = 0.003) and maximum depth (p = 0.0008) variables were more statistically significant than river kilometer (p = 0.02) in predicting species richness. Comparisons with historical ISMP data Abundance of largemouth bass, green sunfish, and the three non-native cyprinids in ISMP samples collected in the Grand Valley since 1986 were plotted to determine if there were trends in those populations (Figs. 22 and 23). Largemouth bass occurred in the Grand Valley reach of the Colorado River in most years since 1986 and appeared to be steadily increasing in abundance since 1993. Green sunfish abundance was generally much higher than for largemouth bass over the period of sampling and exhibited a more erratic abundance pattern since 1986. The highest recorded abundance of green sunfish ever was in 1998, but it was difficult to determine if abundance of that taxon was stable or increasing over time. Abundance of non-native cyprinids fathead minnow, red shiner, and sand shiner in ISMP samples collected in the Grand Valley since 1986, suggested that abundance varied dramatically over time, especially for the latter two taxa (Fig. 23). Sand shiner abundance was more stable since 1986, but all species were relatively more abundant in samples collected in the late 1980's and early 1990's compared to more recent years such as 1997 and 1998. -20-