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2003 and 2004 was similar in most reaches but increased slightly in LD2 in 2004 and declined in <br />WH2 in the same year. <br />We also recaptured tagged smallmouth bass during 2004. One individual captured in <br />lower Lodore Canyon originated in the downstream Jensen-Ouray reach (pers. comm., R. <br />Brunson, Utah Division of Wildlife Resources). We also recaptured three tagged bass (240, 271, <br />340 mm TL) in the Whirlpool Canyon reach, fish that were marked in conjunction with an <br />abundance estimation and removal study in that area (M. Fuller, pers. comm, U. S. Fish and <br />Wildlife Service). <br />It appears from seine and drift net sampling data that smallmouth bass first reproduced in <br />Lodore Canyon in 2002 in limited numbers. The upstream range expansion of smallmouth bass <br />in Lodore Canyon continued through 2005 when small age-0 bass were noted nearly to the head <br />of Lodore Canyon in autumn (unpublished data). It is possible that Lodore Canyon was colonized <br />by fish that escaped over the spillway from Flaming Gorge Reservoir during releases in 1997 and <br />1999. However, if that were the case, we would expect higher abundance of, and more <br />reproduction by, smallmouth bass in upper Lodore Canyon and Browns Park. The opposite <br />pattern seems to prevail; more bass and most reproduction occur in downstream reaches of <br />Lodore Canyon. Low levels of smallmouth bass were present in Lodore Canyon since 1994 to <br />1996 sampling. It is possible that recent increases were the result of a slowly expanding <br />population between 1994 to 1996 and2002 to 2004. <br />Reasons for the recent large increase in abundance of channel catfish and smallmouth bass <br />in Lodore Canyon are not precisely known but are likely related to low flows and warm water <br />conditions present in the Green River beginning about 2001. Prior to then, higher base flows <br />prevailed and temperatures were cooler. Perhaps those warm water conditions promoted <br />successful smallmouth bass reproduction (but not channel catfish) beginning in 2002 in Lodore <br />Canyon. Prior to that, reproduction and recruitment may have been limited by cooler summer <br />temperatures which limited reproduction directly, and delayed hatching or limited growth of <br />smallmouth bass so that their overwinter survival was poor. It is also possible that sufficient <br />numbers of smallmouth bass had not yet invaded Lodore Canyon prior to 2002 to permit <br />59