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increase. Channel catfish abundance in LD4 in 2002 to 2004 was similar to that in Whirlpool Canyon in the same period. Size structure of channel catfish in electrofishing samples in Lodore Canyon changed between the two periods, mainly because of increased abundance in 2002 to 2004 (Fig. 33). In general, during both periods larger fish (> 300 mm TL) were more common in the upper reaches of Lodore Canyon and smaller fish were more common in lower Lodore Canyon; the pattern is more obvious in the recent period. Similar to lower Lodore Canyon, channel catfish in Whirlpool Canyon in the 251 to 300 mm TL size class dominated populations, although a few very large fish were also present. No small channel catfish were sampled in Lodore Canyon, perhaps indicating absence of reproduction by that species there. Small channel catfish were present in downstream Whirlpool Canyon. Smallmouth bass distribution and abundance in Lodore Canyon increased dramatically in the 2002 to 2004 period compared to 1994 to 1996 (Fig. 34); CPUE data showed a significant increase (Table 8). Only a single smallmouth bass was collected from 1994 to 1996 by electrofishing and was found in reach LD3. Now smallmouth bass occupy all Lodore Canyon reaches and increased in abundance in a downstream fashion, where they now constitute > 6% of the fish community in LD 4 and > 10% of the fish community in Whirlpool Canyon. Seine samples showed a similar pattern, as smallmouth bass reproduction was first noted in lower Lodore Canyon in 2002 (N = 4, 13 to 85 mm TL) and was more progressively widespread in 2003 and 2004. Smallmouth bass were not found in Browns Park. Size structure of smallmouth bass captured in 2002 to 2004 suggested a population invading from downstream, as the few fish present upstream were relatively large. Based on the low numbers of small fish upstream, reproduction there was presumed low or absent (Fig. 35). In reaches LD3 and LD4, modal size was smaller at 201 to 250 mm TL and a wide variety of sizes of smallmouth bass were present, including small and very large fish. In Whirlpool Canyon, modal size continued to decline as fish in the 151 to 200-mm TL size class were most abundant. 35