9588

• UCREFRP Catalog Number: 9588
• Author: Bestgen, K. R. and e. al.
• Title: Population Status of Colorado Pikeminnow in the Green River Basin, Utah and Colorado.
• USFW Year: 2005.
• USFW - Doc Type: Fort Collins, CO.
• Copyright Material: NO

reduction of about 63% over the duration of the sampling period. Confidence limits for
abundance estimates in years 2000 and 2003 did not overlap. Regression analysis of loge
abundance as a function of time (N = 4) showed a negative relationship (loge abundance =
633.26 - 0.3131*year, rZ = 0.97,p = 0.016). Consistent with abundance estimates, numbers of
unique animals captured declined steadily over the study period from 265 in 2000 to 106 in 2003.
White River abundance estimates had moderately good precision, with CV's ranging from 13 to
20%.
The only abundance estimate not within expectations for all river reaches and years was
for the White River in 2000. In that year, one 1,240-mm TL fish was captured, and because of
the extremely low predicted probability of capturing this fish (0.000062), this individual inflated
the Huggins model abundance estimate by over 16,000 individuals. That individual was
removed from the data and the analysis re-run to arrive at the more realistic abundance estimate
reported.
Colorado pikeminnow recruits in the White River were rare during the study period and
ranged from 45 (SE = 14) in 2001 to 0 in 2003, reflecting a decline in the number of recruits in
the White River during this study. Confidence limits for abundance estimates of the few recruits
present in the White River 2000 and 2001 did not overlap with and were higher than estimates in
2002 and 2003. Estimates of Colorado pikeminnow recruit abundance in the White River were
less precise than abundance estimates for adults, with CV's that ranged from 31 to 90%.
Abundance of adult Colorado pikeminnow in the middle Green River was the highest of
any of the reaches studied in the Green River Basin but exhibited a pattern of decline similar to
that observed in the White River. Adult Colorado pikeminnow abundance was high in 2000 at
an estimated 1,613 (SE = 149) fish, but declined steadily to 1,184 (SE = 115) in 2001, to 834 (SE
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