| Razorback
Sucker Recovery on the Lower Colorado River |
| |
 The
razorback sucker (Xyrauchen texanus) is a
rare fish species endemic to the Colorado
River basin, including Arizona. It has a
long, high, pronounced hump or keel on its
back (originating just behind the head),
from which the name is derived. The head
and body are dark brown to olivaceous, and
the sides are brownish fading to a yellowish
white abdomen. The razorback's mouth faces
downward, having the lower lip widely separated
into two lobes by a deep groove. Razorback's
feed on algae, aquatic insect larvae, detritus
(decaying organic matter), and plankton.
Razorback suckers live up to 50 years, reach
lengths of 36-39 inches, and weigh up to
13 pounds.
Location and
Habitat:
Razorback suckers occur in medium to large rivers with swift turbulent
waters, as well as slower flowing backwater areas and impoundments. Historically,
they were found throughout the Gila River basin in Arizona and the Colorado
River basin in Wyoming, Colorado, Utah, Nevada, Arizona, and New Mexico.
Due to severe population declines, razorbacks are presently located above
Lake Powell in the upper Colorado River basin and in Lakes Mead, Mohave
and Havasu in the lower Colorado River basin (distribution
map). Populations have been established in the lower Colorado River
and in several other locations through stocking. Since the late 1980's,
Arizona Game & Fish Department has attempted to establish populations in
the Verde and Salt Rivers through stocking, but few fish survive.
Current Status:
Razorback suckers are fully protected in the state of Arizona and are restricted
from fishing. Razorback's are also listed as endangered
by the U. S. Fish and Wildlife Service (since 1991; 56 FR 54957).
Potential Threats:
Habitat alteration and destruction (primarily due to flow regulation),
decline in water quality, and direct competition and predation by non-native
fishes are likely responsible for the decline of the razorback sucker populations.
Flathead catfish, carp, largemouth bass, bluegill, tilapia, green sunfish,
and crayfish are species that typically prey upon or compete with razorbacks.
Current recovery efforts involve reintroducing adult razorbacks in order
to escape predation by resident sportfish. In order to enhance razorback
reproduction and recruitment, stockings should be in areas with low densities
of these impeding species.
Current Research:
Information regarding life history (reproduction, maturity, etc.) and biological
requirements (food and habitat) or preferences for razorback sucker is
limited. Objectives for our recent research have been to study use of various
habitat types by adult razorback suckers in the Imperial Division, lower
Colorado River. In these studies, we set out to determine patterns of habitat
use, develop a predictive model for preferred habitat types, and determine
if off-channel restoration activities by the U. S. Bureau of Reclamation
were beneficial to razorback suckers. We conducted our studies by monitoring
use of existing habitats by razorback suckers implanted with ultrasonic
transmitters. Preliminary results of this study have shown that off-channel
(backwater) habitats were preferred over main-channel or side-channel habitats.
 A
second study was recently conducted to determine the potential for interactions
between flathead catfish (Pylodictis olivaris) and the endangered razorback
sucker in the lower Colorado River. The flathead catfish is a predatory
fish introduced into the Colorado River system to provide anglers with
a sport fishing opportunity, but may also prey upon native fish species
such as the razorback sucker. To estimate the potential for interaction
between flatheads and razorbacks, we concurrently tracked ultrasonically
tagged individuals over a two year period to determine habitat type preference
and overlap in habitat use between these two species.
Flathead catfish were shown to prefer main- and side-channel habitats while
razorback suckers preferred side-channels, backwaters, and impoundment
habitats. There was moderate overlap in habitat use between the two species,
occurring predominantly in side-channel habitats, but further evaluations
revealed that flathead catfish and razorback suckers rarely coexisted in
the same location. As a result of this work, we suggest that flathead catfish
are moderately likely to prey upon hatchery-reared adult razorback suckers
released into the lower Colorado River.
It should be noted, however, that although their co-existence in a particular
site is rare, predation risk is greatly increased during movements among
habitat types. We anticipate a shift in research focus to identify habitat
preferences by other potential predators and habitat overlap with razorback
suckers.
This recovery project is part of a Cooperative Agreement between United
States Bureau of Reclamation and Arizona Game and Fish Department.
For more information
contact:
Joe E. Slaughter IV, Arizona Game and Fish Department, 5000 W. Carefree Highway Phoenix, AZ 85086-5000
.
Phone: (623) 236-7663 E-mail: jslaughter@gf.state.az.us
Kari Ogren, Arizona Game and Fish Department, 5000 W. Carefree Highway Phoenix, AZ 85086-5000
.
Phone: (623) 236-7665 E-mail: kogren@gf.state.az.us
|
| |
| back
to top |
|
|
|
| Related
AZGFD Info |
 |
|
|
|
| |
| External
Resources [More] |
|
|
|
 |
| NOTE:
External sites will open in a new browser
window. |
|
|
