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Eddies The occurrence and surface area of eddies varied directly with discharge (Figure 8), and appeared to be a function of river hydraulics. Eddies provide a food source and habitat for many chubs and suckers. Roundtail chubs are often abundant along "eddy fences", or interfaces between main current and backflow of eddies where they feed on insects drifting in the main channel that are swept into eddies (Valdez et al. 1982) . Shorelines and Rubble Flats --- Shorel ine habitat did not appear to vary with discharge (Figure 9). Although never a constant area, dramatic changes in this habitat did not occur with flow and stage changes. Shoreline habitats ~nd associated features often support the majority of riverine fish populations (Hynes 1970). Their consistent area and physical nature (lack of turbulence associated with midchannel habitats) may explain their importance as fish habitats. Rubbl e flats occurred only at flows between about 5,000 and 12.000 cfs (Figure 9). This habitat appears to be important to some species of fish that associate with shallow riffles, such as speckled dace and young suckers. Isolated Pools Isolated pools occurred at most flow stages (Figure 9), as a result of low-lying areas losing contact with the river as discharge decreased. In three field seasons of seining in the Colorado, Gunnison and Dolores Rivers, Valdez et al. (1982) found many non-native species but few native fishes stranded and dying in isolated pool s. Apparently, the native fishes are keenly aware of changing flow stages and leave backwaters and side channels before they become isolated pools. Pools The trace of the thalweg in March revealed a single pool area about 15 feet deep immediately downstream from the Battlement Mesa Bridge. As discharge increased, velocity through this area increased changing the pool to a deep run. Pool-like character was observed for this area only at the lowest flows (Table 1). It is currently bel ieved that Colorado squawfish spawn in riffles at the upper end of resting pOOls (Archer and Tyus 1984) in much the same manner as the northern squawfi sh of the Co 1 umbi a Ri ver (Beamsderfer and Congleton 1981). Seethaler (1978) first hypothesized this idea and it was later tested by Tyus et al. (1982) and Lamarra et al. (1983) in the Yampa River. Recent radiotelemetry studies strongly suggest the use of this habitat type for staging and resting of squawfish during spawning activities (Archer and Tyus 1984). Habitat Dynamics A synthesis of habitat areas over time (Figure 10) and by discharge (Figure 11), clearly shows the total habitat:discharge relationship. During the period 6 June through 2 September, total habitat area was at a maximum during peak flow in late June and declined to a minimum level in late July through early September. 260