7984

• UCREFRP Catalog Number: 7984
• Author: Maddux, H. R., L. A. Fitzpatrick and W. R. Noonan.
• Title: Colorado River Endangered Fishes Critical Habitat - Draft, Biological Support Document.
• USFW Year: 1993.
• USFW - Doc Type: Salt Lake City, Utah.
• Copyright Material: NO

significant habitat type in the Lily Park area. These habitats have been identified as
important areas for adult razorback suckers (Tyus and Karp 1990). Collection of adult
razorbacks in spawning condition in the lower 0.5 mile of the Yampa indicates the presence
of spawning activity in that area (Miller et al. 1982b; Tyus and Karp 1990). Temperatures
in this portion of the Yampa River have not been altered to any degree by human activities
and remain suitable for native fishes. This reach historically supported razorback suckers,
and they remain in low numbers. This reach of the Yampa is considered essential for the
survival of this species due to the presence of constituent elements and its importance to
constituent elements in downstream reaches of the Green River.
Biological Environment
Nutrient input and food sources for adult razorback suckers are present within the reach.
The relatively unmodified nature of the Yampa River system likely results in food supply
levels similar to predevelopment. The introduction of nonnative fishes is probably the
greatest alteration to the historical Yampa system. Miller et al. (1982b) found 13 nonnative
fish species within this reach. Nine native fish species were collected in the same area. The
potential for competition and predation between these nonnative species and native species is
high. Virtually all 13 species of nonnative fish found in this reach have the potential to prey
on and/or compete with native species. Maintenance of a natural (historical) hydrograph may
help limit further encroachment by nonnative fishes. The presence of nonnative fishes has
not caused the extirpation of adult razorback sucker and other native species from this reach,
and razorback sucker spawning continues in the lower portion.
Relationship to Additional Selection Criteria:
For the razorback sucker, additional selection criteria were developed to assist in the
selection of proposed critical habitat designations. This reach of the Yampa River meets
those criteria.
Presence of Spawning Population
The collection of adult razorback suckers in spawning condition in the lower Yampa River
for several years is strong indication of spawning within this reach (Miller et al. 1982b).
Tyus and Karp (1990) postulated that razorback suckers spawning in the lower Yampa River
was historic, and that the fish exhibited fidelity to that spawning site as evidenced by
repeated captures and recaptures of the same fish.
Nursery Habitat
There are no indications of razorback spawning in the Yampa River in the upper portion of
this reach. However, backwaters and other potential nursery habitats do exist throughout the
reach, particularly in the Lily Park area (Miller et al. 1982b).
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