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Discussion Based on our analyses, no significant habitat partitioning could be identified between Colorado squawfish and the six sympatric species examined. Age-0 Colorado squawfish showed high habitat overlap with three introduced fishes--red shiner, sand shiner and fathead minnow (Table 2). The C/E of Colorado squawfish and each of these three species was positively correlated in the Colorado River, but not in the Green River (Tables 3 and 4). In contrast, the habitat overlap of Colorado squawfish with the two native species examined--Gila spp. and speckled dace--was moderately high and less than that of Colorado squawfish with the introduced species. Matthews and Hill (1980) found relatively little habitat partitioning among fishes in a shallow, sand-bottom stream compared to that of fishes in more diverse environments (see for example Werner et al. 1977). The dynamic nature of the discharge-influenced, predominately sand-bottom habitats of the Green and Colorado rivers may partially explain the lack of clear distinction in habitat use among the fishes that we examined. Moreover, the habitat parameters used in our analyses were quantified by relatively gross measurements when compared with those of other studies (e.g. Baker and Ross 1981). Only two depth, velocity and substrate measurements were made at the location of each seine haul, and some seine hauls covered large areas (ca. 250 mZ). The independent habitat variables used in our analyses might not adequately describe variation among the habitats sampled. Position of the fish in the water column, an important component in the habitat partitioning of fishes in other studies (Baker and Ross 1981), might also be important. High turbidity precludes the collection of such data in the Colorado River system. The pooling of the data