56 



Population estimates in 1975 and 1976 were considered significantly 

 different if 80% confidence intervals did not overlap. Of these estimates, 

 numbers of age II and older brown trout in the Hildreth Extended (2), 

 Barretts Upstream Extended (15), and Barretts Downstream (18) Sections 

 increased significantly between years. Numbers of age II and older brown 

 trout within each of the lower four sections were not significantly 

 different between years. Numbers of age II and older rainbow trout in 

 the Hildreth Extended (2) Section were significantly greater in 1976, 

 although this increase partially reflects a greater movement of spawning 

 fish rather than an absolute increase in residents. Numbers of rainbow 

 trout within the Wheat (27) and Westside Canal (29) Sections were not 

 significantly different between years. 



The increase in the estimated numbers of age II and older brown trout 

 between years in the Hildreth Extended (2), Barretts Upstream Extended 

 (15), and Barretts Downstream (18) Sections may partially reflect low 

 annual rates of population decrease resulting from greater flows between 

 the 1975 and 1976 estimates (Table 22). Although flows in the lower 

 river also increased dramatically, annual rates of population decrease 

 in the Wheat (27), Westside Canal (29) and Anderson Lane (38) Sections 

 were more than two times that in the other sections, suggesting factors 

 other than flow were limiting the survival of brown trout in these sections. 



Between 1975 and 1976, the biomass of age II and older brown trout 

 increased significantly in the Hildreth Extended (2) and Barretts 

 Downstream (18) Sections, was not significantly different in the 

 Barretts Upstream Extended (15) and Blaine (52) Sections, and decreased 

 significantly in the Wheat (27), Westside Canal (29), and Anderson Lane 



