7355

• UCREFRP Catalog Number: 7355
• Author: Wydoski, R. S.
• Title: Assessment of Introduced Sport Fishes As Potential Competitors with or Predators upon the Rare Colorado River Fishes with Reference to Fishery Management in Kenney Reservoir.
• USFW Year: 1987.
• USFW - Doc Type: Denver, Colorado.
• Copyright Material: NO

INTRODUCTION
During a meeting on June 17, 1986 pertaining to establishment of a Colorado
squawfish (Ptychocheilus lucius) sport fishery in Kenney Reservoir on the
White River, Colorado, the C lorado Division of Wildlife (CDOW) requested that
the U.S. Fish and Wildlife Service (FWS) summarize data to demonstrate the
potential significance of predation or competition by largemouth bass
(Micropterus salmoides) and other warmwater sport fish in establishing a
Colorado squawfish in the reservoir. This summary would be used by the CDOW
in preparing a final version of the Kenney Reservoir lake management plan.
The draft lake management plan specifies that "esocids, percids, and
smallmouth bass [Micropterus dolomieui] be prohibited in Kenney Reservoir and
the White River" (Martinez 1986). It also recommends to stock "channel
catfish [Ictalurus punctatus] in 1987" and, if the Colorado sqawfish fishery
option is not implemented by 1988, to stock "centrarchids".
This report provides a brief summary of the potential competition/predation of
channel catfish and selected centrarchids (largemouth bass; bluegill, Lepomis 4
macrochirus; and crappies, Pomoxis sp.) on establishing a fishable Colorado
squawfish population in Kenney Reservoir.
BACKGROUND
The Colorado River originates as cold, clear, headwater streams in the Rocky
and Uinta Mountains that drops into a dry desert where spectacular canyons
have been carved out over the years. The mainstem Colorado River and its
major tributaries were historically warm and turbid that changed dramatically
in volume from melting snow during runoff and suddenly during flash flooding.
Alterations of the natural river ecosytsem by water development projects have
resulted in changes in the physical, chemical, and biological characteristics
of the Upper Basin. Dams have modified the riverine environment into lentic
habitats, changed natural streamflows and water temperatures, and obstructed
natural fish passage. Daily, monthly, and seasonal streamflows vary as a
result of water storage during runoff and releases at the dams that are
dependent upon irrigation, power, and other downstream water demands.
The endemic Colorado squawfish, humpback chub (Gila cypha), bonytail chub
(Gila elegans), and razorback sucker (XX_rauc?hen texanus) have declined in
numbers and these species are now absent-from parts of their historic range.
The low population levels of these rare fishes are correlated with poor
reproductive success (i.e., recruitment related to survival during the early
years of life) and that, in turn, is correlated with environmental changes.
The environmental changes have provided favorable habitat for introduced
fishes. Forty species from eleven families have been introduced either
intentionally through stocking sport fish or accidently by release of live
bait fish and have become established in the Upper Basin. Today, nonnative
fishes comprise nearly two-thirds (65.6X) of the 61 species in the Upper
Basin. Many biologists who work with the rare endemic fishes believe that
competition and predation are significant factors in the decline of the
endemic species (Kaeding 1986).
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