7963

• UCREFRP Catalog Number: 7963
• Author: U.S. Fish and Wildlife Service.
• Title: Streamflow Needs of Rare and Endangered Fishes
• USFW Year: 1990.
• USFW - Doc Type: Yampa River Interim Flow Recommendations - Final Report.
• Copyright Material: NO

Stream-flow needs of native fishes in the Yampa River are influenced by many
factors including time of year, life history stage, and flow requirements of
sympatric species. Reproductive activities of the target fishes, (i.e.,
Colorado squawfish, razorback sucker, and humpback chub) are closely associated
with flow, temperature and other parameters associated with normal spring
runoff conditions. Alteration of this hydrologic event may affect initiation
of Colorado squawfish and razorback sucker migrations, and spawning of these
and other native fishes, including bluehead (Catostomus discobolus) and
flannelmouth (C. lat_ ipinnis) suckers. Maintenance of low, stable flows in late
summer and fall is conducive to growth and survival of young Colorado
squawfish, and young of other species as well. Stable winter flows through ice
breakup are considered important to overwinter survival of young and adults in
some locations. Abrupt fluctuations of water level from late summer to spring
could strand larvae, stress adults, and influence reproduction. Life histories
of target fishes are associated with natural flow events that comprise the
Yampa River hydrograph.
Quantification of Instream Flows
The Service, and others, have expended substantial amounts of time and manpower
in making instream flow recommendations using physical simulations of habitats,
in developing temperature and flow models, in analyzing stream sediment-water
flow relationships using historic and current flow patterns, and others.
Physical modelling to date has not demonstrated predictive capability relative
to cause-effect relationship with the distribution and abundance of the
endangered fishes in the Green River basin (Rose and Hahn 1989). This is
attributed to the variability of the environment (e.g. seasonal fluctuations in
discharge, temperature, food base, species abundance, etc.) and interactions
among environmental variables; logistical problems associated with studying
fishes in large, turbid rivers; changing environmental conditions during study
periods; and the introductions of nonnative fishes. In addition, where
physical habitats have been measured, their use by the fish may only reflect
temporary, seasonal, or marginal habitat use. Thus, caution must be exercised
in determining flow requirements of fishes in decline. Ecological data and
professional judgement must be recognized as critical in interpreting fish
requirements in complex systems.
Flow recommendat"ions to provide needed habitat and to satisfy life history
requirements of endangered fishes in the Yampa-Green River system must be
approached with great caution. Decline of the Colorado squawfish in other
rivers of the upper basin apparently continues, as evidenced by very low
numbers of young fish, and failure in detecting spawning areas. Recruitment of
the razorback sucker is not sufficient to sustain the species anywhere at this
time, but higher numbers of the fish, and the identification of two spawning
areas in the Yampa and Green rivers offer some promise for recovery.
Experimentation with flows to which the endangered fishes may not respond
favorably should be conducted elsewhere; not in the Yampa River. A reduction
in the 1989 year-class of Colorado squawfish in the upper Green River suggests
that additional factors may influence successful recruitment in this species
even if flow conditions in nursery habitats are presumably adequate. This is
indicative of the precarious existence of the endangered Colorado River fishes.
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