9294 - Laserfiche WebLink

Home Browse Search

backwaters, but at the 94% level. Turbidity did not appeaz to be a factor in backwater use by olorado s u sh. Main channel turbidity was greater at used backwaters in August and September, but was lower in July. Turbidity at the backwater mouth was higher in August, but in ~~ the rest of the backwater only in July. Discriminant modeling was slightly better for Colorado squawfish backwaters than chub backwaters. However, models developed from pooled data still could not explain more than 7% of the variance between used and unused backwaters. Models based on monthly sampling were able to explain up to 28% of the variance between Colorado squawfish backwaters and unused backwaters. Classification error rates for pooled and monthly samples varied form 15% to 41%, and were, mostly, above 30%. Error rates were driven by inability to properly classify used backwaters. Cover, temperature, width and depth, again, were important discrinunating variables. Fish Community and Catch-ner-unit-effort Fourteen species offish were captured during backwater seining: six native and eight nonnative: A list of species and their occurrence are given in Table 9. Both chubs and Colorado squawfish were. commonly_ encountered, although chubs were generally found only in Desolation Canyon and Colorado squawfish became most numerous in Gray Canyon. Red shiners and fathead minnows were, by far, the most numerous species inhabiting backwaters in both canyons. One interesting point to note is the presence of four razorback sucker larvae in samples collected in Desolation Canyon during June (n=3) and July (n=1) of 1994. Backwater descriptions for these fish are presented in Appendix A. CPUE for all species varied by month and year. Table 10 includes CPUE statistics for chubs and Colorado squawfish. Table 9. Fish species caught in backwaters in Desolation and Gray canyons of the Green 24