9565

• UCREFRP Catalog Number: 9565
• Author: Bestgen, K. R. and e. al.
• Title: Population Status of Colorado Pikeminnow in the Green River Basin, Utah and Colorado
• USFW Year: 2007
• USFW - Doc Type: Transactions of the American Fisheries Society
• Copyright Material: NO

1364

BESTGEN ET AL.

Yampa River

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1999 2000 2001 2002 2003

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ce
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White River

1600~ ~
1200
800
400
o ....
1999 2000 2001 2002 2003

Middle Green River

2000~ ~
1500
1000
50g .,..

1999 2000 2001 2002 2003

1200 rCSOlatiOn-Graranyon

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2000 20Gl 2002 2003

Lower Green River

600
450
300
150
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2000 20Gl 2002 2003

Green River Basin

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3750
2500
125~ . -+. ,

1999 2000 2001 2002 2003

FIGURE 3,-Abundance of Colorado pikeminnow adults C?450 mm TL; filled diamonds) and recruits (400-449 mm; squares)
in the Yampa, White, middle Green, Desolation-Gray Canyon, and lower Green River reaches as well as the entire Green River
basin, Utah and Colorado, 2000-2003. Error bars represent the 95% confidence intervals (which may be obscured by the
symbols in the case of recruits). The open diamond in the Green River basin panel includes the estimated abundance for the
unsampled Desolation-Gray Canyon and lower Green River reaches (2001 estimates); the open circle is the estimate for the
Yampa, White, and middle Green River reaches only.

slightly to 143 in 2003. The abundance estimates for
the middle Green River reach had the best precision of
all reaches studied, CVs ranging from 9% to 18%. The
relatively low CVs were due to the relatively large
number of captured and recaptured fish.
Colorado pikeminnow recruits in the middle Green
River reach were moderately abundant compared with
the other reaches sampled in 2000 and 2001 (107 and
133 individuals, respectively) but declined in 2002 and
2003. The confidence interval for the abundance
estimates of recruits in the middle Green River in
2001 did not overlap with those for 2002 and 2003.
Estimates of Colorado pikeminnow recruit abundance
in the middle Green River had CV s that ranged from
19% to 70%.
The abundance estimates for adult Colorado pike-
minnow in the Desolation-Gray Canyon reach of the
Green River and the lower Green River reach were
lower than that observed in the middle Green River
reach. The abundance of adult Colorado pikeminnow

in the Desolation-Gray Canyon reach was 699 in 2001
and 621 in 2003, an 11 % decline over the study period.
However, pairs of point estimates had overlapping
confidence intervals and thus did not indicate signif-
icant differences. Regression of abundance as a
function of time (n = 3) showed a slightly negative
but nonsignificant relationship (loge [abundance] =
124.97 - 0.0592. year; r2 = 0.35, P = 0.595). The
number of unique animals captured declined from 208
in 2001 to 99 and 100 in 2002 and 2003, respectively.
Abundance estimates in the Desolation-Gray Canyon
reach had moderately good precision (CV = 16-22%).
The Desolation-Gray Canyon reach consistently sup-
ported the highest average annual abundance of Colorado
pikeminnow recruits during the study period. Recruit
abundance was highest in 2001 (163 fish) and lowest in
2002 (72) in 2002; the confidence intervals overlapped in
all years. The CVs ranged from 20% to 39%.
The abundance of adult Colorado pikeminnow in the
lower Green River reach was the lowest of all Green