7418

• UCREFRP Catalog Number: 7418
• Author: Tyus, H. M. and C. A. Karp.
• Title: Stream Flow Needs of Rare and Endangered Fishes, Yampa River, Colorado.
• USFW Year: 1988.
• USFW - Doc Type: Vernal, Utah.
• Copyright Material: NO

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habitats (Tyus 1987). Spawning activity by razorback sucker has been observed
in lower Yampa River near its confluence with the Green River (McAda and
Wydowski 1980, Tyus 1987). Although records for some years are not complete,
razorback sucker spawning was initiated on the ascending limb of the spring
hydrograph, and extended into highest peak flows in 1975 (McAda and Wydowski
1980), and in 1981, 1984, 1986, and 1987 (FWS unpublished data, Tyus 1987).
Water temperatures were variable during this period, but always exceeded 15C.
Capture of ripe adult and larval fish indicates that reproduction is
successful (McAda and Wydowski 1980, Tyus 1987). However, other than the
tentative identification of two juvenile fish from Green River in 1977 (Holden
1978), recruitment in razorback sucker has not been documented in the Colorado
River basin (McAda and Wydowski 1980, Hinckley 1983, Tyus 1987). Habitat
requirements of this species in riverine environments are not well known
because of the scarcity of extant populations (~anigan and Tyus 198$) and
absence of juvenile/subadult life history stage (Tyus 1987). Apparent decline
of this species towards local extinction warrants greater protection.
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