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isolated pools are not desirable habitat for smallmouth bass. Regardless, fish composition data from isolated pools supports the notion that native fish can survive in the areas with limited bass abundance, but in areas where smallmouth bass are abundant such as in main channels, native fishes do not persist. Yampa River age-0 smallmouth bass age and growth.-smallmouth bass sagittal otolith daily increments were obvious and generally easy to read, a trait that was enhanced by the large size of the otolith relative to cypriniform fishes. Limited smallmouth bass hatching in the Yampa River in 2005 began in mid-June and extended into late July, but the bulk of fish hatched from early to mid-July in about a 2-3 week period (Fig. 9). Regular spawning (about 5-8 d incubation time prior to hatching, depending on water temperature) began when water temperatures were consistently above about 16°C. Smallmouth bass growth was water temperature dependent and typically very fast, even when water temperatures were cooler (Fig. 10). For example, fish collected in mid-August grew on average about 1.2 mm/d at those warm water temperatures. Even fish collected in late September, which experienced a warm summer and a cooler September period, grew at a rate of about 0.7 mm/day. These are very high growth rates, compared to native cypriniform fishes. For example, mean growth rates of Colorado pikeminnow larvae in laboratory studies and in backwaters of the Green River grew from 0.3-0.5 mm/day, under high growth conditions (Bestgen 1996, Bestgen et al. 2006a). Growth rates of razorback suckers are even lower (Bundy and Bestgen 2001). Yampa River smallmouth bass hatching and growth rate information is specific to only 2005. This is especially true since we only examined a relatively small sample and because the thermal and flow regime of the Yampa River in 2005 was quite different than in other years in the recent period (see earlier figures). However, results of preliminary studies presented here showed that otolith information may be useful to identify the timing and duration of smallmouth bass spawning seasons in Upper Colorado River Basin streams. Collection of such data under a variety of flow and temperature regimes, including using data from historical bass samples, may be useful to be able to predict timing and intensity of spawning. This information will be useful 18