9555

• UCREFRP Catalog Number: 9555
• Author: Bestgen, K. R., C. D. Walford, A. A. Hill and J. A. Hawkins.
• Title: Native Fish Response to Removal of Non-native Predator Fish in the Yampa River, Colorado.
• USFW Year: 2007.
• USFW - Doc Type: 140,
• Copyright Material: NO

(Graham and Orth 1987; Bestgen and Bundy 1998; Bundy and Bestgen 2001) Increment counts
were verified with a second reader. In general, otolith increments were obvio~s and easy to read.
smallmouth bass hatching dates were estimated by subtracting age in days frdm the date of
capture, assuming that the first daily increment was deposited at hatching. Pe~ the literature, a
1:1 relationship between age in days and otolith microincrement count was as~umed. Fish
growth rate was estimated by subtracting length at hatching (mean literature value of 5.5 mm TL,
Carlander 1977) from length at capture, and dividing by age in days.
Native fish evaluation data analysis.-Data analysis for this report
presentation of species richness and percent composition of fishes by control
and habitat type. We rely on this approach because that is the main data prey
for historical data, with which we make comparisons to our own data. We al
logistic regression analyses to estimate presence of native fishes as a function
sampling, control or treatment reach, habitat type (isolated pool or main char
smallmouth bass presence and abundance. We also conducted logistic regret
mostly via
treatment reach
technique
o conducted
of year of
iel), and
ion analyses to
estimate proportion of native fishes as a function of year of sampling, control or treatment reach,
habitat type (isolated pool or main channel), and smallmouth bass presence a
Overdispersion in these models was corrected by multiplying the standard er
parameter estimates by the square root of the deviance. This approach gives
larger estimates of the variance and generally results in fewer significant stal
estimates, so it is a conservative approach. Model selection was by AIC. A
conducted with Statistical Analysis Systems software, Proc Genmod and Prc
NC).
RESULTS AND DISCUSSION
Yampa River stream flow and water temperatures.-We present
historical and present-day streamflow and temperature patterns of the Y
believe they are a significant influence on recent changes in fish distribution
abundance.
of the
ire realistic and
cal tests for
ses were
GLM (SAS, Cary
ve information on
River because we
abundance
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