9566

• UCREFRP Catalog Number: 9566
• Author: Miller, W. J., D. E. Rees and J. A. Ptacek.
• Title: Final Report - Elkhead Reservoir Escapement Recovery Program Project No.
• USFW Year: 2005.
• USFW - Doc Type: 118, Investigation of nonnative fish escapement from Elkhead Reservoir.
• Copyright Material: NO

Executive Summary
An escapement study was conducted during 2003 and 2004 during periods of high spill rates
associated with snowmelt runoff at Elkhead Reservoir near Craig, Colorado. Nets were
placed and monitored at strategic locations on the spillway and outlet structure. Fish
escapement was confirmed at all locations, but was greatest during periods of high discharge
at the spillway. Relative abundance data indicated that bluegill and black crappie are the
species that escape with the greatest frequency; however, they have been captured
infrequently in slackwater habitats in the Yampa River downstream from Elkhead Reservoir.
A diel pattern of escapement was also observed.
The recommended screening for the reservoir to minimize escapement includes installation
of screens on all controlled outlets of the enlarged reservoir. To the extent practicable, the
controlled outlets should be used to the maximum release capacity during runoff when flows
are released over the spillway. This operational adjustment should shorten the magnitude
and duration of flows exiting the reservoir by way of the spillway.
This screening option recognizes that there could be some escapement during highest flows.
The species that are of most concern are northern pike and smallmouth bass. Based on the
data collected in 2003 and 2004, few smallmouth bass and no northern pike were captured
during this study.
Key words: catch rate; diel; entrainment; escapement; outlet structure; outflow; spillway;
reservoir; runoff.
FINAL REPORT - Elkhead Reservoir Escapement, Project No.: 118 Page i
Miller Ecological Consultants, Inc. May 20, 2005