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At the laz est scale video h taken at low flow was used to determine lar e- g ~p y g scale changes in emergent bars. Year to year changes in habitat availability were determined from videography from three different years for the 10-km reach. On the video maps, habitats were identified, delineated and classified by the bed- or barform that caused flow stagnation (backwaters). Habitat depth, as determined from field measurements, was also noted. The videography was used to link the changes in topography and habitat availability measured at the study baz to the changes in channel form within the 10 km reach. Surrogates for habitat availability, in the form of shoreline complexity indices were also evaluated. Statistics from the GIS of detailed bar topography were used to calculate Gosse's (1963) complexity index, the ratio of line length to total reach length for each contour of each year. Biology The 16 km nursery habitat study reaches were selected based on high catch rates of age 0 Colorado pikeminnow during fall ISMP sampling on the middle and lower Green River. The upper study area was located within the Ouray National Wildlife Refuge (NWR), between River Kilometer (RK) 421.6 and 405.5 as measured upstream from the confluence with the Colorado River. The lower study area was at RK 91.7 to 75.7, centered on Mineral Bottom. Three sampling trips were executed each year beginning in spring 1992, continuing in mid summer, early fall and the following spring, and ending in spring 1997. The sampling schedule followed each cohort of pikeminnow through their first year of life, beginning post- spawn, and ending the following spring before the spring runoff. On each trip all backwaters and other low-velocity areas with young-of--year habitat potential were sampled for fish by seining, and measured. Overall length and three width transects were taken to estimate total area and total volume of the habitat. Sub-surface temperatures (°C) were recorded at each transect, and turbidity was gauged on a subjective scale from clear to turbid. The turbidity and temperature of the adjacent main channel were taken at the same time. Cumulative degree days were calculated from the main channel USGS gage near Green River, Utah (#09315000), and compared with thermograph data from the main channel and a series of backwaters. Each sampling trip was coordinated with avideo-imaging overflight conducted by the Bweau of Reclamation (BOR). Individual habitats were mapped onto aerial video prints and overlays to evaluate their persistence through time. Fish were collected from each habitat using a 1.2 m by 4.6 m seine, with 1.6 mm mesh size. The number of seine hauls varied from one to three depending on the size of the habitat. For each habitat, catch-per-effort (CPE) in #fish/100m2 and #fish/100m3 was estimated by dividing the number of YOY pikeminnow collected by the area and volume sampled in all seine hauls. Total CPE was estimated for each trip by dividing all pikeminnow collected by the total area and volume sampled. Sampling Efficiency Evaluation of sampling efficiency was conducted in 1994 on the lower Green River, centered on the Mineral Bottom nursery habitat section, and on one occasion in the Colorado River from RK 153 -132 in April. On the Green River, sampling occurred following each nursery habitat sampling trip (spring, summer, fall). Sub-sections of nursery habitat backwaters vii