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1 ma im rove the licabili of the model to chan es in individ 1 n y p app ty g ua ursery habitats m response to flow regime in future studies. The azeas of individual habitats mapped in the field were compared to the azea of those habitats mapped on the GIS video maps from the 1.5-km reach. The relationship between area of habitat interpreted from the videos and from the field maps was linear (r-Z = 0.89, df = 5, p = 0.001). The area interpreted from the video prints tended to slightly underestimate the field measurements. Videography may be an appropriate tool for assessing trends in total nursery habitat availability, although it cannot assess the quality of the habitats, in terms of depth. The Gosse and Wetzel complexity indexes were not appropriate tools for assessing habitat availability from remotely sensed data. The total habitat azea was estimated from digitized photos from the 10 km reach in 1963 and compared with habitat azea estimated from digitized videography in 1992 to1994. The 1963 mapping flows (10 to 28 m3/s [353-988 cfs]) were lower than mapping flows in 1992, 1993 or 1994, which were 45-55 m3/s [1590-1942 cfs]. Similazly to 1993-1994, the available habitat in 1963 was the result of a high water yeaz (1962) followed by a low water yeaz. The total available habitat area estimated in 1963 was lower than that estimated in either 1992, 1993 or 1994. From this limited comparison, total habitat azea does not seem to have decreased overall since dam completion. j, Biology:Ouray The results indicated that YOY Colorado pikeminnow showed a preference for large, deep backwaters. Backwaters used by Colorado pikeminnow had mean length 1.8 times that of unused backwaters. Likewise, mean width was 1.7 times greater and mean volume 2.2 times greater. Backwater size and depth were obvious criteria for establishing minimum backwater selection characteristics for YOY Colorado pikeminnow monitoring. Researchers established a protocol calling for sampling backwaters with minimum surface area of 30 m2 and minimum depth of 0.3 m for the Interagency Standardized Monitoring Program (ISMP) (LTSFWS 1987). This depth figure is nearly identical to the mean depth value (0.33 m) for backwaters in which Colorado pikeminnow were collected at Ouray NWR. The minimum surface azea in ISMP protocol is much lower than the mean for Colorado pikeminnow backwaters at Ouray NWR (992 m2). However, Colorado pikeminnow were caught in backwaters as small as 19 m2. Turbidity has also been noted as a distinguishing characteristic for Colorado pikeminnow use. Backwaters with Colorado pikeminnow were more likely to have higher turbidity ratings than unused backwaters. Temperature appeazed to play a role in habitat selection by Colorado pikeminnow in this study during spring and summer. In summer samples, backwaters containing Colorado pikeminnow were significantly warmer than others, but the difference was only 1.0°C. Similar result were seen in spring backwater samples, but significance was atp<0.10. Backwaters used in the spring were actually closer (+2°C) to main channel temperature than unused backwaters (+3.1 °C). The backwater classification with mean surface azea (999 m2), mean depth (0.42 m), cover, and aspect values closest to those of the "average" backwater used by Colorado pikeminnow were secondary (scour) channel backwaters. These backwaters aze large, deep and turbid, and tend to be perennial habitats that change primarily as a result of river levels, but are available every yeaz. Because of their wide mouths and positioning in the river system, they x