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

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10 cm. By August, this proportion declined to about 50 percent with
40 percent of the fishery made up of large (,20 cm) fish. The
percentage of large fish declined in October to approximately
20 percent. We also broke down the densities of small fish in an
attempt to possibly follow any major movement of small fish though the
reservoir. Fish <10 cm were abundant in the Cebolla and Sapinero
basins in June but declined dramatically in August and October. This
in itself is misleading. These declines are probably influenced by
small kokanee moving closer to the surface to feed on the zooplankton.
Young kokanee were frequently observed feeding near the surface which
would make them virtually invisible to hydroacoustic gear.

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DISCUSSION

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Fish passage through Blue Mesa Powerplant is not new. It's common
knowledge that some fish are lost from the reservoir due to powerplant
operations. A percentage of these fish do survive and contribute to
the downstream fishery. Actually. facilities were designed,
installed, and at one time operated to recapture kokanee that had
successfully passed downstream and were migrating back upstream to
spawn. However, what has changed is a growing concern for threatened
and endangered fish further downstream. In 1991, FWS recommended test
flow criteria for the Gunnison River near Grand Junction, Colorado.
Flow criteria were designed to guide reservoir releases to more
closely mimic historical spring/summer flows (McAda and Kaeding 1991)
Blue Mesa Reservoir provides the largest volume of water available to
meet these criteria. Long-term recommendations will be provided by
FWS in 1998.

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Blue Mesa Reservoir represents a premier kokanee fishery not only for
angler harvest, but also as an important source of kokanee eggs for
hatchery production in Colorado and other states. Colorado Division
of Wildlife (CDOW) expressed concern that increases in spring releases
may impact this important resource.

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Reclamation funded this study to take a precursory look at fish
transport associated with flow recommendations and determine if
losses were impacting the reservoir's kokanee salmon fishery.
If there was evidence suggesting that significant fish losses
were occurring, a second, more refined sampling effort would
then be warranted.

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