9533

• UCREFRP Catalog Number: 9533
• Author: Muth, R. T. and E. Wick.
• Title: Field Studies on Larval Razorback Sucker in Canyonlands National Park and Glen Canyon National Recreation Area, 1993-1995.
• USFW Year: 1997.
• USFW - Doc Type: Fort Collins.
• Copyright Material: NO

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the early life history of razorback sucker, with high priority placed on projects concerning larval
distribution, abundance, and habitat use.
As the Endangered Fish Program Coordinator, Ed Wick was assigned to the
Cooperative Park Studies Unit at Colorado State University and had the opportunity to work
closely with the Colorado State University Larval Fish Laboratory (LFL) and other federal and
private agencies to develop and implement field or laboratory studies on razorback sucker
biology, reproduction, and early life history and on physical conditions in the Green River
related to present flow regimes. Research projects conducted cooperatively with the LFL over
the three-year endangered fish program included (1) field studies on larval razorback sucker in
CANY (Green and Colorado rivers) and Glen Canyon National Recreation Area (GLCA;
Colorado River inflow to Lake Powell), (2) laboratory studies to evaluate the effectiveness of
various light trap designs for capturing and retaining larval and early juvenile razorback sucker,
Colorado squawfish Ptychocheilus lucius, and bony tail Gila elegans, (3) laboratory studies on
use of the fish anesthetic tricaine methanesulfonate (MS-222) to immobilize razorback sucker
larvae to facilitate field identification of living specimens, and (4) genetic analysis of selected
field-collected sucker larvae to confirm suspected identities based on morphological criteria.
Other cooperative studies involved the U.S. Fish and Wildlife Service and included (1)
assessment of sediment deposition patterns on the primary razorback sucker spawning bar
located in the middle Green River near Dinosaur National Monument, (2) assessment of the
effects of flood duration on razorback sucker nursery habitat in the lower Green River, CANY,
(3) development of a flow-routing model for the Green River, and (4) evaluation of movements
of adult razorback sucker in the Yampa and Green rivers within or near Dinosaur National
Monument using radiotelemetry. This report covers NPS/LFL field studies on larval razorback
sucker in CANY and GLCA during 1993-1995.

Goals and objectives of NPS/LFL field studies on larval razorback
sucker.-Qverall goals were to (1) advance the knowledge of razorback sucker larvae and
potential recruitment in lower portions of the upper Colorado River basin, and (2) refine or begin
to develop techniques for the study and management of razorback sucker populations
throughout the upper basin. The study objective in 1993 was to document occurrence and
relative abundance of razorback sucker in nursery habitats at selected locations in the lower
Green River within CANY and Colorado River inflow to Lake Powell within GLCA. In 1994,
study objectives were to (1) further document occurrence and relative abundance of razorback
sucker larvae in nursery habitats at selected locations in the lower Green River within CANY
and Colorado River inflow to Lake Powell within GLCA, (2) document occurrence and relative
abundance of razorback sucker larvae in nursery habitats at selected locations in the middle
Colorado River within or bordering CANY, (3) refine sampling techniques for larval razorback
sucker, (4) use preliminary results of the laboratory study on use of MS-222 to immobilize living
razorback sucker larvae to develop techniques for identifying live fish larvae in the field and
transporting larval razorback sucker to rearing facilities, and (5) describe the diet of nonnative
adult red shiner Cyprinella lutrensis collected from nursery habitats at selected locations in the
lower Green and middle Colorado rivers within or bordering CANY and document predation on
native fish larvae. Study objectives in 1995 were to (1) further document occurrence and
relative abundance of razorback sucker larvae in nursery habitats at selected locations in the
lower Green River within CANY and Colorado River inflow to Lake Powell within GLCA, (2)
preliminarily assess the feasibility of selective, partial control of adult red shiner by blocking
their access to portions of nursery habitats at selected locations in the lower Green River within
CANY, (3) develop procedures for marking larval razorback sucker in the field by adapting

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