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TABLE 3. -Relationship between river-wide mean CPE (CPM/hr; all sampling reaches combined) and population estimates for years when population estimates were available (Osmundson and Burnham 1998; Nesler 2000; Osmundson 2002). River Years rz P SE Nesler (2000) Colorado 1991-1997 -0.19 0.82 127.70 Green 1992- 1997 0.49 0.07 1400.67 Yampa i 992- 1997 -0.21 0.75 65.21 White 1992- 1997 0.77 0.01 58.97 Osmundson and Burnham (1998) Colorado 1992-1994 0.76 0.22 34.7b Osmundson (2002) Colorado 1998-2000 0.41 0.36 15.39 -------------------------------------------------------------------------------------------- Osmundson and Burnham (1998), Osmundson (2002) Colorado 1992-1994; 1998-2000 0.24 0.18 88.72 annual histograms for the White and Yampa rivers shifted among size groups but reflected mostly adult-sized fish in all yeazs. In contrast, the Green and Colorado rivers varied considerably among years and reflected more young fish than adults in some years. These differences may reflect strong yeaz classes entering the adult population. This was most evident in the Green River during 1989-1993 and 1995-2000 (Figure A-1). Fewer fish were captured in the Colorado River, so shifts in length-frequency distribution were not as evident (Figure A-2). However, large numbers of small fish were captured in some years. Average length-frequency distributions provide the best evidence for differences among rivers (Figure 9). The Yampa River contained only large fish; no fish smaller than 400 mm was collected during this study. In contrast, a large percentage of fish collected from the Green River were less than 400 mm. Small fish were also collected from the Colorado and White rivers, but not to the same extent as the Green River. Figures 10 and 11 compare length-frequency distributions for the upper and cower portions of the Green and Colorado rivers. In both rivers, more small fish were found in lower reaches than in upper reaches. 14