7124 ‎(2)‎

• UCREFRP Catalog Number: 7124
• Author: McAda, C. W. and R. S. Wydoski.
• Title: Technical Papers
• USFW Year: 1980.
• USFW - Doc Type: \
• Copyright Material: YES

10 native and 19 introduced fish species in the main
stem of the upper Colorado River. Alterations in the
river have produced a favorable environment for
exotic species, which have become so numerous that
competition for food and space may be a major factor
in the decline of native species (Miller 1961; Minckley
and Deacon 1968; Minckley 1973-. Seethaler et al.
(1979) outlined many of the factors involved in the
decline of the native fish fauna.
Holden and Stalnaker (1975x) believed that the
Yampa River in northwestern Colorado plays a vital
role in the continued existence of endemic fishes in the
upper basin. The present study was begun to deter-
mine the importance of the Yampa River in the ecology
of the razorback sucker and to locate other reaches
inhabited by this species.
The depletion and extinction of native fish in various
waters has alarmed many biologists and certain seg-
ments of the public in recent years (Minckley 1965;
Minckley and Deacon 1968; Miller 1961, 1963, 1972;
Deacon 1968; Constantz 1974; Reiger 1977-. The result
has been an increase in efforts to ensure the preser-
vation of the native species. Natural resource
managers, traditionally oriented toward sport fish and
wildlife, must assume the responsibility for the
management of all native fishes if they are to fulfill
their obligation to the public and the resource (Pfister
1976). Information on habitat requirements, distribu-
tion, abundance, and life history is needed to facilitate
the management of all native fishes-particularly
those of the Colorado River basin. To mitigate the
impacts of further alterations of the river on the native
species, managers must know the ecological and bio-
logical requirements of the fish. In carrying out this
study, we had four objectives: (1) to determine the dis-
tribution and relative abundance of the endangered
fish species, as well as the other species, found in the
Colorado River drainage; (2) to determine movements
of the razorback sucker, with special emphasis on the
extent and timing of the spawning migrations from
the upper Green River into the Yampa River; (3) to
delineate spawning areas for the razorback sucker and
determine the ecological requirements for spawning;
and (4) to summarize current knowledge of the life
history of the razorback sucker.
Study Area
The primary collection sites (Fig. 1) were at Echo
Park (station 3) and the Walker Wildlife Area (station
8). Sites farther up the Yampa River at Lily Park (sta-
tion 1) and Castle Park (station 2) were also exten-
sively sampled, but no razorback suckers were col-
lected. Island Park (station 4) was sampled twice and
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Lake Powell ; COLORADO
Fig. 1. Location of sampling stations (solid circles) along the
Colorado, Green, and Yampa rivers, Utah-Colorado: 1, Lily
Park; 2, Castle Park; 3, Echo Park; 4, Island Park; 5, Horse-
shoe Bend; 6, Ouray; 7, Sand Wash; and 8, Walker Wildlife
Area. (Most razorback suckers were collected at stations 3
and 8.Open circles show cities or towns.)
Horseshoe Bend, Ouray, and Sand Wash (stations 5, 6,
and 7, respectively) were sampled once each during
exploratory collecting for razorback suckers.
The Yampa River at stations 2 and 3 flows through
narrow canyons and has sections of deep, fast water.
The shoreline and river bottom are composed of rocks
ranging from a few millimeters to 20 m in diameter.
Quiet eddies are created behind the larger boulders. At
station 1 on the Yampa River and stations 4, 5, 6, and
7 on the Green River, the stream flows through open
valleys. The water velocity is low and the river is
shallow; sand or silt is the main substrate.
The riparian vegetation along the Yampa and Green
rivers characteristically consists of box elder (Ater
negundo-, cottonwoods (Populus spp.-, willows (Salix
spp.-, and tamarisk (Tamarix pentandra-; typical vege-
tation on the hillsides includes rabbit brush (Chryso-
thamnus spp.), big sagebrush (Artemisia tridentata),
and Utah juniper (Juniperus osteosperma-. Holmgren
(1962) provided a detailed discussion of the vegetation
in this area. The region is arid, having an average
annual precipitation of 25 cm (Vanicek 1967-. Air tem-
peratures range from a high of 40 C in summer to a low
of - 25 C in winter. Water temperatures range from
0 C in winter to 30 C in late summer (Vanicek 1967-.