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

raft-based (White River and Desolation-Gray Canyon Green River reaches) electrofishing as the
standard technique, sampling during each occasion began at the top of each reach and proceeded
downstream. Electrofishing units were either pulsed-DC Coffelt or Smith-Root types, with one
or two anode booms with spheres. Two boats were typically used on each sampling occasion,
one on each shore, and one or usually two netters captured stunned Colorado pikeminnow. All
nearshore habitat that was likely to hold Colorado pikeminnow was electrofished.
Approximately 7 to 10 d elapsed between short-term sampling occasions in each reach
and year to allow for sufficient mixing of marked and unmarked fish. In the Yampa River in
2000, only a single electrofishing boat was used, but that effort was supplemented with passive
sampling gears such as fyke nets and trammel nets in low velocity areas. A block-and-shock
technique was sometimes used, where a large, nearshore, quiet-water area was isolated from the
main channel with a trammel net and electrofishing commenced inside the block net. Colorado
pikeminnow were captured by netters or in trammel nets as they attempted to leave the backwater
for the main channel. Use of these techniques was limited in other years and reaches.
In most reaches, sampling focused only on Colorado pikeminnow, although other
endangered fishes, and non-native northern pike, were sometimes captured. Colorado
pikeminnow were measured (TL, nearest mm), weighed (nearest g), scanned for the presence of a
PIT tag, and unmarked fish (>150 mm) received a PIT tag inserted into the body cavity just
posterior to the pelvic girdle. The initial capture and release location (nearest 0.1 RK) was
determined from river maps and a Global Positioning System unit and all Colorado pikeminnow
were released within 0.15 km of their capture location.
Additional data utilized in this study was from an Interagency Standardized Monitoring
Program (ISMP, McAda 2002). The ISMP sampled adult and sub-adult Colorado pikeminnow
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