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abundance were obtained using an electrofishing boat that was operated parallel to the shoreline in measured distances. At least 20 fish per species per sample were weighed, measured and stomach contents removed for identification and enumeration, This was done to establish a size-dependent vulnerability estimate for native fish species for each nonnative fish species, In addition to field surveys, we have been conducting large enclosure{exclosure experiments (3 x 3 m cages) to determine vulnerabilities of YOY squawfish to different species and sizes of nonnative fish predators. Squawfish ranged from 25 to 40 mm TL in these experiments, In addition, we designed some cages with refuges to determine if young squawfish will successfully avoid nonnative fish predators if they are given an opportunity, During 1994, we also initiated a number of cage experiments dealing with temperature fluctuations and food availability in backwaters and how these factors may affect YOY squawfish growth and survival, RESULTS To date, our estimates of species densities suggest that red shiners, channel catfish, green sunfish, and smallmouth bass are the dominant exotic species in the Ouray nursery habitat section. Crappie, northern pike and fathead minnows also have been observed but appear to be in relatively low densities, Cage experiments testing vulnerability of young squawfish to different predators suggest that smallmouth bass (all sizes) pose the greatest threat with individual fish consuming up to 25 squawfish per week. Channel catfish and green sunfish also exhibit considerable predation potential with individuals consuming up to 16 squawfish per week, Red shiners exhibited surprisingly low predation rates (<5 squawfish per week), but may still be important predators on larval squawfish, We began development of the foodweb for this area including all sizes of fish and their interactions, The strengths of those interactions have been estimated directly through stomach analysis. It is clear from the foodweb that most of the energy in this section of river flows through the red shiner compartment. The results of the cage experiments investigating the role of temperature and food availability on YOY squawfish growth suggest that areas with high temperature fluctuations are indeed less than optimal for maximum growth. Deep backwaters and the mouths of all backwaters appear to provide lowest temperature fluctuations as well as the greatest food availability. Unfortunately, these are the exact areas where non-native predators concentrate. Thus, a trade- off exists between backwater type (and quality) and nonnative fish predators. VII, Recommendations: MANAGEMENT IMPLICATIONS- These studies taken together are beginning to suggest that while deep backwaters provide the most optimal habitats for YOY squawfish, the density of nonnative fish predators makes these habitats basically unusable, This is especially due to ~