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I I I I I I I I I I I I I I I I I I I Size ofYOY small mouth bass is similar to that reported last year for 1998 but growth rates appeared faster in 2000 than in 1999. Density Estimation Y AMPA RIVER Fish density estimates were similar in 1998 and 1999 at the Duffy Reach on the Yampa River, but estimates were significantly (alpha = .05) lower in 2000 than the two previous years (Table A3). The Duffy Reach is 7.2 km long and is electro-fished every year to indicate population abundance over a longer section. The length of this station has varied in each year. In 1998 the take-out was 0.8 km further downstream, in 1999 the starting point was 0.8 km upstream to match the area mapped by sonar. In 2000 neither the extra upper or lower 0.8 km was sampled. The data in Table A3 are from the same starting and ending points. Since the Duffy Reach is long, it is well suited to make inferences about local fish movements and the higher number of recaptures provide a more precise measurement for trends in abundance. It is felt the data for the Reach strongly indicates abundance of fish > 15cm was less in 2000. It appears this could be related to the much lower flows in 2000 compared to flows in 1998 and 1999. The Duffy Reach electrofishing station includes the Duffy Site. Fish density estimates from the mapped Duffy Site are higher than from the Duffy Reach in all three years (Table A4). This is probably due to different habitat compositions. A very large deep run dominates habitat composition in the DullY Site and is located immediately upstream of the hydraulic control used to divert water to the Duffy Tunnel intake. The disproportional high availability of deep habitat in the Survey Site probably explains the higher fish density there. At flows over 150 cfs this habitat is a run, but at under 150-cfs velocities drop and it is considered a pool (Figure 3). The longer Reach has been sampled each year to determine how 33