7047

• UCREFRP Catalog Number: 7047
• Author: Tyus, H. M. and C. A. Karp.
• Title: Habitat Use and Streamflow Needs of Rare and Endangered Fishes in the Green River, Utah
• USFW Year: 1991.
• USFW - Doc Type: Final Report.
• Copyright Material: NO

Study Abstracts
All reports completed under the Flaming Gorge Interagency Agreement of
1986 were abstracted. Abstracts were copied verbatim if the report contained
an abstract, or one was subsequently published. In cases in which no abstract
was furnished by the authors, we abstracted the conclusions section. Abstracts
are generally organized under the appropriate initiative, but there was some
overlap between studies.
Study 1: Summer and autumn requirements of age-0 Colorado squawfish in the
Green River.
Report I- Distribution, habitat use, and growth of age-0 Colorado squawfish
in the Green River Basin, Colorado and Utah. (Tyus and Haines 1991)
Age-0 Colorado squawfish Ptychocheilus lucius (n = 11,379) were captured
as larvae and postlarvae in drift nets and seines in the Green and Yampa
rivers from 1979 to 1988. Larvae were captured in drift nets (n = 601) for
about 2 to 6 weeks in June and July. Small postlarvae were captured by seining
shoreline habitats (n = 3,079) in July and August. In September and October,
postlarvae were most abundant (n = 6,459) in low-gradient reaches of the
Green River. Catch data indicated that the postlarvae moved from the Yampa and
Green River spawning areas and were concentrated about 150 km downstream by
autumn of each year. Spring sampling indicated that young fish (n = 1,240)
overwintered in areas occupied the previous autumn. Postlarvae captured in
the Green River (n = 5,043) most frequently occupied shoreline embayments
(backwater) that were relatively warm (x = 17.0 °C), deep (x = 38 cm), large
(z = 826 m) and turbid. Abundance and size of young Colorado squawfish in the
Green River were inversely correlated with high summer and autumn flows which
inundated nursery habitats. Seine catches of young squawfish in four years of
sampling the upper and lower Green River in autumn and the following spring
were not reliable in assessing overwintering mortality of age-0 Colorado
squawfish, presumably due to differences in capture vulnerability between
seasons. Survival of small fish in spring indicated their tolerance to
prevailing winter conditions. (Abstract)
Report 2- Movements and habitat use of young Colorado squawfish in the Green
River, Utah. (Tyus 1991)
Habitat use and movements of young Colorado squawfish Ptvchocheilus
lucius were determined by seining 1,194 of the fish in shoreline areas. A
total of 922 of these were fin-clipped in selected habitats and 230 (25%) were
subsequently recaptured. Most young Colorado squawfish were captured in
shallow shoreline embayments (backwaters; 85% of captures), where they were
most abundant in spring (April; 68%). Some individuals used more than one
habitat and moved between backwaters, shoreline eddies, and main-channel
runs. A diel pattern of backwater use was associated with warmer water
temperatures, especially in spring (April) when backwater temperatures
exceeded river temperatures. (Abstract)
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