8117

• UCREFRP Catalog Number: 8117
• Author: Modde, T. and G. Smith.
• Title: Flow Recommendations for Endangered Fishes in the Yampa River.
• USFW Year: 1995.
• USFW - Doc Type: Denver, CO.
• Copyright Material: NO

RM downstream in the Green River (Tyus 1987). Humpback chub are believed to
spawn at several locations within Yampa Canyon (Karp and Tyus 1989). Because the
Yampa River is the last major tributary of the Upper Colorado River Basin whose
hydrograph has not been substantially altered by water development, it exerts a major
impact on the biology of native fishes, both listed and nonlisted species. The
magnitude of this impact was identified in the Biological Opinion for the operation of
Flaming Gorge Dam (USFWS 1992) which requires the synchronization of dam
releases with Yampa River peak flows to simulate a natural hydrograph in the Green
River.

On a larger geographic scale, the decline of the "large river" fishes in the
Colorado River drainage has been attributed to the failure of recruitment resulting from
_ a number of factors, primarily habitat alteration associated with water development and
interactions with nonnative fishes (e.g. Behnke and Benson 1988, Minckley et al.
1991, Tyus 1991). The magnitude and pattern of flows is the primary habi!at feature
influencing the reproductive success of the endangered fishes occupying tne Green
and Yampa rivers (Tyus and Karp 1989, 1990, Tyus and Haines 1991, Modde et al.
accepted for publication). Flows cue the initiation of spawning migrations, spawning
(Tyus 1987, Tyus and Karp 1989, Nesler et al. 1988), remove sediment from spawning
substrate (Harvey et at. 1993) which would maximize egg survival, and transport larval
fishes to nursery sites (Tyus 1991). As with many riverine species (Welcomme 1985),
reprod uctive behavior of the "large river" fishes of the Colorado River is adapted to the
seasonal hydrology and the annual, seasonal and daily variation inherent in rivers of
arid landscapes. Despite the overwhelming data supporting the association of
reproductive biology of endangered fishes to flow patterns, little information exists on
their tolerance for change. Thus, in the absence of specific information on how native
fish respond to modified environments, this report proceeds with the assumption that
virgin flow conditions (those when fish were common, Le Quartarone 1993) represent
the environment most likely to allow recovery and maintenance of these species (Tyus
1986, 1994).

OBJECTIVE AND APPROACH

The objective of this report is to present and integrate existing hydrological
and biological information with ecological principles to present flow recommendations
that will recover and maintain endangered fishes in waters influenced by Yampa River
flows (i.e. Middle Green River). Existing information on endangered fish distribution,
abundance, spawning migrations and reproductive requirements (much of which was
previously presented byTyus and Karp 1989), comparisons of native and nonnative
fish distribution within the Yampa River, and a synthesis of newly acquired virgin flow
estimates were used as the data base on which flow recommendations were based.
In addition, the RIP instream flow review (Stanford 1994) was used as a guideline in
developing flow recommendations. The approach taken was to review existing
information and integrate this material with the recent RIP instream flow review
(Stanford 1994) and ecological literature to provide recommendations that will recover
endangered fishes of the Yampa and Green rivers.

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