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• UCREFRP Catalog Number: 7300
• Author: Tyus, H. M. and C. A. Karp.
• Title: Habitat Use and Streamflow Needs of Rare and Endangered Fishes, Yampa River, Colorado.
• USFW Year: 1989.
• USFW - Doc Type: Biological Report 89‎(14)‎,
• Copyright Material: NO

Table 6. Delineation of critical river reaches for rare and endangered Colorado River fishes in the Yampa River, witlt
notes on potential limiting factors.
Life history stage Location (RK)a Season Potential limiting factors
Colorado Squawfsh
Adult 0-224 All year Spring peak flows; overbank flooding;
Concentration 82-198 August-May seeps in spawning reaches; number
Migration 0-224 May-August of ripe females; angling or other
Spawning 6-51 June-August incidental takes; siltation of
Larva 0-50 July-August spawning substrate, competition and
Juvenile 0-224 All year predation with nonnative fishes;
food availability; stream blockage;
low flows late summer, fall, and
winter; stability of winter flows.
Humpback Chub
Adult 0-90 All year Spring peak flows; availability of
Concentration 6-64 All year shoreline eddy habitat and deep
Spawning 19-64 May-July canyon habitat; competition and
Larva 0-64 May-July predation by nonnative fishes.
Juvenile 0-90 All year
Bonytail Chub
Adult 0-16 All year Factors unknown.
Razorback Sucker
Adult 0-21 All year Spring peak flows; overbank flooding;
Spawning 0-6 April-June number of reproducing adults;
Larva 0-6 April-June competition and predation by non-
native fishes; lack of substantive
recruitment to juvenile life history
stage.
a Numbers represent river kilometers (rounded) upstream from the mouth of the Yampa River.
occupied habitat in the White River due to blockage of
access to overwintering areas (Martinez 1986).
Localized water input at the spawning grounds may
provide orientation cues for spawning Colorado
squawfish, and thus, significance of groundwater and
surface inflows in these areas, relative to survival of
endangered fishes, should be further investigated.
The reproductive success of Colorado squawfish
depends on a number of interdependent factors,
including the number of spawning adults (particularly
ripe females), river discharge, sediment load,
temperature, and photoperiod. Condition and
physiological readiness are also important factors. The
presence of adult Colorado squawfish in inundated
shorelines and lowlands during spring runoff suggests
that such behavior, and associated feeding, may offset
the large energy expenditure required for migration and
spawning. Thus, natural overbank flooding in spring and
the consequent increased availability of floodplain
nutrients (Welcomme 1979) are important factors in
physiological readiness of Colorado squawfish, The loss
of successful reproduction in one or more years could
effect a further decline of Colorado squawfish.
Colorado squawfish eggs are adhesive, and hatching
success may depend on their attachment to substrate
surfaces, Therefore, availability of cleaned cobble and
boulder surfaces in spawning areas may be limiting, if
flushing action from peak flows is significantly curtailed
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