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

migration, spawning, and creates nursery habitat for early life stages) and maintain the
river channel geomorphology such that habitats necessary for endangered fishes
continue to exist. A slight deviation in the interim recommendations for baseflows is
proposed, such that, flows during successive years fluctuate according to the
magnitude of the water year. The recommendations for minimum flows are that: 1)
baseflows generally remain above the monthly 80% exceedance for virgin flows
between August through March period as shown in Table 4, and 2) rates of daily
variation throughout the year do not materially deviate from virgin conditions. The
relative impacts of a minimum flow on native and nonnative fishes is unknown at this
time. The U.S. Fish and Wildlife Service suggests an adaptive approach to defining
baseflow recommendations by evaluating the response of native and nonnative fish
interactions following low flow years, i.e., greater than 80% exceedance. The Use of
the 20% and 80% exceedance values has been standard practice for developing
Biological Opinions in Region 6, U.S. Fish and Wildlife Service for defining high and
low flows years. The same standards were proposed by Maheshwari et al: 1995.
The importance of the Yampa River's relatively natural flow magnitude and
variation to the life histories of endangered fishes fully justifies that the flow
recommendations be implemented and evaluated. Because daily, seasonal and
annual flow variations may be essential to the life history of the endangered fishes of
the Yampa River, the continuous pattern of a natural hydrograph should be maintained
rather than a truncated design of constant monthly values. Below are specific
rationale for U.S. Fish and Wildlife Service recommendations associated with the
runoff and baseflow period.

Spring (March 21 - June 21)

Colorado sQuawfish

In the spring adults move into flooded or protected areas where they fed and
ostensibly prepare for spawning. Annual spawning migrations are associated
with the decline of the hydrograph and increasing temperatures. Between 1981-
1988: spawning of Colorado squawfish occurred approximately 26 days following
the start of migration movement with minimum temperatures of 190 C and
maximum temperatures of 240 C. Spawning generally occurred earlier in low
water years and later in high water years. Seasonal peak flows are necessary
to cue movement, build and maintain gravel spawning bars, and sculpt river
channels to create eddy habitats used by staging fishes.

Razorback sucker

Razorback sucker spawning migration is initiated during the increasing limb of
the natural hydrograph and spawning occurs between temperatures of 120 C to
160 C. High flows are necessary to clean spawning gravel and cobbles and
transport larval fish from spawning sites to nursery sites downstream in the lower
gradient reaches of the Green River.

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