7816

• UCREFRP Catalog Number: 7816
• Author: Tyus, H. M.
• Title: Movement and Habitat Use of Young Colorado Squawfish in the Green River, Utah
• USFW Year: 1991
• USFW - Doc Type: Journal of Freshwater Ecology
• Copyright Material: YES

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Movements and Habitat Use of Young Colorado Squawfish
in the Green River, Utah
Harold M. Tyus
U.S. Fish and Wildlife Service
1680 West Highway 40, Suite 1210
Vernal, Utah 84078

ABSTRACT

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 was 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.

INTRODUCTION

Colorado squawfish, Ptvchocheilus lucius, is listed as an
endangered species by the U.S. Fish and Wildlife Service (1989).
Although reasons for its decline and endangered status are not well
understood, low standing crops in some locations may be due to high
early-life mortality (Kaeding and Osmundson 1988). Loss and alteration
of backwater habitats used by the young fish have also been suggested as
reasons for decline (Holden and Wick 1982). An interagency recovery
program has suggested habitat management is needed to develop or
maintain nursery areas for the various species of endangered fishes
(Rose and Hamill 1988), but information about which specific habitats
should be managed for Colorado squawfish or how to manage them is scant. ~
Colorado squawfish incorporate a considerable amount of movement
into their life cycle (Tyus 1986). Adults migrate down- and up-stream to
reach suitable spawning grounds (Wick et al. 1983; Tyus 1985, 1991). The
newly-hatched larvae enter stream drift and are transported downstream
(Haynes et al. 1984, Nesler et al. 1988). By late summer, the postlarvae
occupy shoreline habitats that may be many kilometers distant from where
they were spawned (Tyus and Haines 1991). As the larvae leave the drift,
they are captured in shoreline habitats, primarily backwaters (Holden
and Wick 1982, Tyus and Haines 1991). The use of backwaters in summer
has been well documented, but it is not known if the young select
backwaters during other seasons. It has been suggested that main-channel
habitats are used in winter because many of the backwaters that the fish
use in summer are frozen (Holden and Wick 1982).
As in Colorado squawfish, other cyprinid fishes exhibit seasonal
movements in rivers, including longitudinal stream drift (Brown and
Armstrong 1985), and lateral movement into shorelines (Welcomme 1979).
Fish may leave the main river channel and use shallow areas, ostensibly
in response to physiological requirements such as feeding, or use such
areas as refugia from larger, piscivorous fishes (Harvey 1987). Young
Colorado squawfish have swimming ability similar to other fishes (Berry
and Pimentel 1985), and they may make daily movements in response to
local stimuli. If such movements exist, a knowledge of them and their
associated environmental conditions could be of importance in designing
recovery programs for this endangered fish.

43
Journal of Freshwater Ecology, Volume 6. Number 1 - March, 1991