WSP05499

• File Number: 8200.766
• Description: Gunnison River General
• State: CO
• Basin: Gunnison
• Water Division: 4
• Date: 4/1/1997
• Author: Mueller and Hiebert
• Title: Assessment of Kokanee Salmon Transport through Blue Mesa Powerplant - Colorado - During the Spring and Summer of 1994-1996
• Water Supply Pro - Doc Type: Report/Study

I
I
I
I
I
I
I
I

I
,
I
I
I
I
I
I
I

I
I

~;j/~~7
~ ~v~

Unfortunately, no passage data is available regarding the numbers
cf fish passing through the Blue Mesa Powerplant prior to the
1992 operational change, nor is there data pertaining to winter
entrainment rates. We believe existing evidence suggests the
1994-1996 spring/summer fish transport through the dam was not
the primary factor influencing the reservoir's kokanee
population. It's estimated only 0.05 to 4.0 percent of stocked
kokanee passed through the dam.

Another species, which reflected a similar decline and even lower
passage rates was rainbow trout. The rainbow trout fishery
declined 43 percent during this same period. This is
particularly relevant, since less than 1 percent (11 fish) of the
fish sampled passing through Blue Mesa Powerplant were rainbow
trout. This evidence suggests that if some other factor, such as
lake trout predation or disease, were responsible for the rainbow
trout decline, it may have also affected the survival of young
kokanee salmon.

INTRODUCTION

A 5-year Gunnison River endangered fish research program was
initiated in 1992 as part of the Recovery Implementation Program
(RIP) for the Endangered Fish Species of the Upper Colorado River
Basin. A component of this program recommended the modification
of Blue Mesa Dam releases to more closely mimic the historic
hydrograph (McAda & Kaeding 1991). More water is being released
during spring runoff and less during late summer, fall, and
winter. In 1992, the Colorado Division of wildlife (CDOW)
contacted the RIP and expressed concern that change in spring
releases may have a significant detrimental impact on the Blue
Mesa Reservoir's popular kokanee salmon and rainbow trout
fisheries.

Each spring fingerling kokanee salmon are released from the
Roaring Judy Hatchery into the Gunnison River. These fish
migrate downstream and enter Blue Mesa Reservoir. It was feared
that during high spring flow, when fingerlings and adult kokanee
are associated with higher temperatures, fish would be
particularly vulnerable to entrainment and downstream passage.
State biologists were concerned that a significant portion of the
reservoir's kokanee fishery could be lost due to higher spring
releases.

3