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backwater temperatures present. Colorado squawfish used backwaters with temperatures of 14.6 °C in the upper Green River, 19.4 °C in the lower (Table 4). Backwaters in which no Colorado squawfish were captured averaged only 12.2 °C and 17.7 oC, in upper and lower areas, respectively. Backwaters that contained Colorado squawfish were deeper than those in which they were absent (t-test, P = 0.05, Table 4). Colorado squawfish were captured in predominately larger backwaters in the upper Green River (t-test, P = 0.05) where average sizes were 269 m2 and 1,158 m2 for backwaters in which the fish were absent and present respectively. Backwater sizes were similar between those that did and did not contain the fish in the lower Green River, where average sizes were 310 m2 and 494 m2, respectively (Table 4). Most of the backwaters occupied by Colorado squawfish were turbid (67% lower; 67% upper Green River), but backwaters in which Colorado squawfish were absent were clear to partly clear (81% lower; 67% upper). Presence or absence of Colorado squawfish was not related to backwater substrate in either nursery area (G-tests; P = 0.3 lower, P = 0.7 upper). Colorado squawfish were sympatric with adults and young of 17 other fish species in backwater habitats. Non-native fishes were the most abundant group in combined autumn seine catches; red shiner Notropis lutrensis (65%) and fathead minnow Pimeahales promelas (16%) dominated the catch. Native species included Colorado squawfish (6%), suckers Catostomus spp. (5%), speckled dace Rhinichthvs osculus (2%) and Colorado River chubs Gila spp. (1%). Other, less common species (<1%), included sand shiner N. stramineus, speckled dace Rhinichthvs rop melas, creek chub Semotilus atromaculatus, redside shiner Richardsonius balteatus, common 10