7305

• UCREFRP Catalog Number: 7305
• Author: Tyus, H. M. and W. B. Harned.
• Title: Distribution, Spawning and Habitat Use of the Razorback Sucker in the Green River Basin, Colorado and Utah, 1979-84.
• USFW Year: 1985.
• USFW - Doc Type: \
• Copyright Material: YES

-7';'

~...............(...........
.~
.. ,

~~

...

i'........<...........<.:.
;I..."

;::.( .
(~

F
1

1

1

j

t
1
1

.

!
}

).
,
-~-_:-~

......

()7 '30S-
...:.----

DISTRIBUTION, SPAWNING AND HABITAT USE OF THE
RAZORBACK SUCKER IN THE GREEN RIVER BASIN, COLORADO
AND UTAH, 1979-84.

Harold M. Tyus and William B. Harned
Field Supervisor, Colorado River Fish Project and Fishery Technician

u.s. Fish and Wildlife Service

ABSTRACT

The distribution and habitat use of the razorback sucker was evaluated by
the capture of 244 razorbacks and radiotelemetry. The fish was most abun-
dant in spring samples and apparently occupied habitats that were not very
accessible to sampling gear the remainder of the year. The center of distri-
bution occurred in the flatwater sections of the Upper Green River and
localized areas at the mouths of tributary streams. Razorbacks were not
collected in whitewater areas. Three spawning reaches were identified by the
collection of 47 razorbacks in br~eding condition, of which 33 were ripe with
strippable sex products. Larval razorbacks were identified downstream of
all three areas. A total of 26 ripe razorbacks were collected from the
Green River from May 3 to June 15, 1984, over sand and gravel substrates.
Water temperatures at the points of capture ranged from 10.5 to 18 C,
averaging 15 C. Ripe females were collected from May 10 to June 14 at an
average water temperature of 16 C. This study indicates that the razorback
is sedentary during most of the year, making only local movements of a
few miles, but undertakes spawning migrations in the spring.

INTRODUCTION

The razorback sucker, Xyrauchen texanus (Abbott), has never been listed
as threatened or endangered by the U.S. Fish and Wildlife Service (1980),
but it has twice been proposed for listin~. It is currently designated
endangered by the State of Colorado (1980). Although once abundant and widely
distributed (Seethaler et ale 1979), its riverine existence is primarily
limited to the Upper Colorado River Basin, where it is found in the mainstem
of the Green and Upper Colorado rivers. Although collectors have encountered
probable spawning agregations there in recent years, young razorback suckers
have seldom been found (McAda and Wydoski 1980; Valdez et ale 1982). The
razorback is still found in mainstem reservoirs in the Lower Colorado River,
but it is presumed that the individuals there are not reproducing (Minckley
1983) and constitute relict populations.

The Fish and Wildlife Service (FWS) and Bureau of Reclamation initiated a
study of the endangered fishes of the Colorado River in 1979, that was
expanded by other funding and continued through 1981 (Miller, et ale 1982).

193