9432 ‎(2)‎

• UCREFRP Catalog Number: 9432
• Author: Modde, T. and M. Fuller.
• Title: Feasibility of Channel Catfish Reduction in the Lower Yampa River.
• USFW Year: 2002.
• USFW - Doc Type: Vernal.
• Copyright Material: NO

because of diversion dams constructed during the first part of the 20th century.
These low-head diversion dams have altered Colorado pi keminnow movement patterns,
disrupted reproductive behavior, and reduced the number of available spawning
sites.
An ancillary part of the passageway evaluation was to follow the movements
of radio-tagged fish during the spawning period in hopes that they might help
identify spawning locations in the Upper Colorado River upstream of Westwater
Canyon. During July of 1996, 1997, 1998, and 1999, the presumed spawning period,
the movements of radio-tagged pikeminnow revealed that they mostly remained
scattered and separated, or in pairs, similar to that noted by McAda and Kaeding
(1991). During July 1997 and 1998, however, one radio-tagged pikeminnow (Code
126) was located in the "vicinity" (1-mile downstream) from an aggregation of
non- radio- tagged pikeminnow (RM 168.8) in the 18-mile reach of the Upper Colorado
River (see Appendix; Table K.9. for an explanation of the numbers of pikeminnow
captured in 1994, 1998, and 1999). While the opportunity existed for this fish
to congregate with other non-radio-tagged fish believed to be spawning, ground
tracking never detected them in close, spatial proximity with each other. No
radio-tagged fish were found near this site during 1999. Tracking protocol
employed during this evaluation may have limited our ability to locate
radiotagged pikeminnow with other congregating pikeminnow during this period.
Only about 10-15 minutes were spent with each individual radio-tagged fish once
they were contacted on any given search date.
Summary
Although 43 Colorado pikeminnow ascended the fish passageway during the
this study, none of the 29 Colorado pikeminnow implanted with radio transmitters
in 1996, 1997, or 1998 ascended the passageway at Redlands. Four pikeminnow that
ascended the fishway in 1999, were radiotagged, and subsequently moved downstream
over the Redlands Diversion Dam did not reascend the fishway.
Radiotelemetry provided data on, 1) the fate of some of the pikeminnow
released upstream of the diversion dam, 2) the duration that they spent upstream
of the diversion dam, 3) documented when they passed over the dam, and 4)
monitored subsequent movements presumed to be related to spawning. A similar
movement pattern was observed following spawning in 1996, 1997, and 1998: nine
radio-tagged pikeminnow returned to the Lower Gunnison River from the Colorado
River during this time. Three returned in 1996, four in 1997, and two in 1998.
The time that they remained in the Lower Gunnison River ranged from late-July to
mid-September. Six of these fish were detected in the Redlands Dam plunge pool
and three fish remained scattered throughout the remaining 2.2-mile reach during
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