9678

• UCREFRP Catalog Number: 9678
• Author: Tyus, H. M. and C. A. Karp.
• Title: Habitat Use and Streamflow Needs of Rare and Endangered Fishes
• USFW Year: 1990.
• USFW - Doc Type: Flaming Gorge Studies - Draft Consolidated Report Preliminary.
• Copyright Material: NO

Report 15- Abundance, Growth, and Diet of Channel Catfish, Ictalurus
punctatus, in the Green and Yampa Rivers, Colorado and Utah (Tyus and Nikirk,
in press).
Channel catfish were widely distributed in 517 km of the mainstream
Green and 74 km of the lower Yampa rivers in 1987 and 1988. The fish was most
abundant in rocky canyon habitats (average stream gradient >2 m/km), where
adult fish comprised 14% of electrofishing and 70% of angling catch. Pectoral
spine sections of 364 channel catfish of 27-756 mm total length ranged in age
from 0 to 22 years respectively, with an average annual growth range of 17-53
mm. No difference in growth or condition factor was detected among catfish
collected in eight river reaches. Growth of channel catfish in the Green River
basin was judged slow in comparison to other areas of the United States and
was attributed, in part, to cold water temperatures, short growing seasons,
and elevated summer flow conditions. Channel catfish consumed a variety of
food items, but piscivory was limited to larger fish (average length 420 mm).
Of 575 stomachs with food (76.2%), 31% contained aquatic invertebrates, 28%
contained vascular plant material, 22% contained terrestrial insects, 10%
contained algae and detritus, and 8.5% contained fish and mice. The abundance,
widespread distribution, and omnivorous feeding behavior of this introduced
fish may affect populations of rare and endangered fishes in the Green River
basin (Abstract).
Report 16- Migrating Mormon Crickets, Anabrus simalex (Orthoptera:
Tettigoniidae), as Food for Stream Fishes (Tyus and Minckley 1988).
Migrating bands of Mormon crickets (Anabrus sim lex) were observed crossing
the Green and Yampa rivers in Dinosaur National Monument, Colorado and Utah,
in 1986 and 1987. Swimming crickets were swept downstream and eaten by four
endemic and seven introduced fish species. Included were two endangered
fishes, Colorado squawfish (Ptychocheilus Lucius) and humpback chub (Gila
cvpha). Direct and indirect effects to aquatic food webs associated with
application of pesticides for Mormon cricket control may pose a threat to
these fishes and to man (Abstract).
Study 5:.Trophic Dynamics and Ecological Interaction in Important Backwater
Habitats.
Report 17- Some Aspects of Trophic Interactions in Selected Backwaters and the
Main Channel of the Green River, Utah (Grabowski and Hiebert 1989):
. Limnological data collected from the Green River and backwaters at
Island Park, Jensen, and Ouray suggest an upstream to downstream trend in
abiotic and biotic characteristics in both the river and backwaters in this
reach of river. Average seasonal water temperature was higher downstream than
upstream, and warmer in the backwaters than at nearby river sites.
. Slightly warmer water temperatures and greater nitrogen and
phosphorous concentrations in Ouray backwaters may stimulate production of
blue-green algae; blue-green algae were a major component of the <25 um size-
fraction of phytoplankton (nannoplankton) collected from backwaters. The
average increase in turbidity in Ouray backwaters was due in part to greater
nannoplankton abundance and higher concentrations of particulate organic
material.
... Zooplankton densities were low in both the river and backwaters,
although greater in backwaters, and generally greater in Ouray backwaters than
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