7080

• UCREFRP Catalog Number: 7080
• Author: Carter, J. G., V. A. Lamarra and R. J. Ryel
• Title: Drift of Larval Fishes in the Upper Colorado River
• USFW Year: 1986
• USFW - Doc Type: Journal of Freshwater Ecology
• Copyright Material: YES

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Drift of Larval Fishes In the
Upper Colorado River
John G. Carter, Vincent A. Lamarra and Ronald J. Rye'
Ecosystems Research Institute
975 South State Highway
Logan, Utah 84321

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ABSTRACT

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Case-Western

Native as well as some non-native fishes in the upper Colorado River
were found drifting during their larval and early juvenile stages of
developnent. Five native fishes (flannelmouth sucker, bluehead sucker,
roundtail chub, speckled dace. and mottled sculpin) dominated the drift with
about 87 percent of the catch. The only 3 non-native species found in the
drift (white sucker, fathead minnow. and g~een sunfish) occurred in very low
numbers. Significantly greater numbers of drifting fishes were found along
the shorel ine than in the midchannel surface zone. larval fish were first
caught in the dri ft when the water temperature reached 160C during a rapid
warming trend in mid-to-late July. About 65 percent of the drift recorded
in the two studies occurred during a two to three week period when water
tempera tures ranged from 18 to 21 oC. duri ng the descend ing 1 imb of spri ng
runoff. A diel pattern in drift densities was seen at both sites. with
highest numbers of larvae caught between 2000 and 0400 hours. and lowest
numbers between 1600 and 2000 hours. This diel pattern suggests that many
of the larval fishes of the Colorado River are photosensitive. and actively
capable of entering and escaping the surface drift currents.

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INTRODUCTION

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The phenomenon of drift among fishes of the upper Colorado River was
only recently described in studies of the federally-endangered Colorado
squawfi sh (Ptychocheil u.! ~). humpback chub (i.U2 ~). and bonyta il
chub (Gila elegans). as well as the candidate razorback sucker (Xrrauchen
texanu~ Intensive studies of fishes in this river system began in the
early 1960's (Banks 1964; Vanicek 1967), and it was bel ieved that young
Colorado squawfish moved little from their spawning site (Holden 1977). A
drift phenomenon for these fishes was not hypothesized in literature until
the completion of the Colorado River Fisheries Project (CRFP) in 1981. In
that report. Tyus et .11. (1982) suggested the possibil ity of drift by larval
Colorado squawfish from suspected spawning areas to confirmed nursery areas
located a considerable distance downstream.
'.
Small mesh drift nets designed to capture drifting ichthyofauna were
first used in the rivers of the upper baSin to locate spawning areas of
endangered fish species. Haynes et ale (1984) first conducted drift studies
in the upper Colorado River within Colorado. and in the Yampa River. starting
in 1979; and Radant et .11. (1983) used drift nets in the White River as part
of the Colorado squawfish investigations within the state of Utah. The
increase in water withdrawal s, flow modifications, and hydropower projects
in the upper Colorado River Basin have prompted further study.

Freshw. B101.

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atom
5-275.

567

~ 1986

Journal of Freshwater Ecology, Volume 3. Number 4 - December. 1986
Copyright 0 1986 by Oikos Publishers. Inc.