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

I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I

corixids, were the principal identifiable food items. Adult red shiner may be an important
predator on native fishes in the Colorado River basin, especially in habitats with low invertebrate
forage during spring and early summer.

. Netting effectively blocked access of adult red shiner into exclosed portions of nursery
habitats while allowing passage of sucker larvae; results suggest that this method of nonnative
fish control could be adapted for broader-scale use.

. Laboratory techniques for marking otoliths in larval razorback sucker were successfully
applied to sucker larvae in the field. Otolith aging of wild-caught razorback sucker larvae can
be used to determine growth rates and exact time of spawning, data which can then be used to
document environmental parameters during spawning and early rearing and evaluate growth
and survival potentials of larvae.

Recommendations

. Management of flows to create and maintain nursery habitats during the criticallarval-early
juvenile period is essential, and actions to improve the quality of nursery habitats through
artificial enhancement of productivity or control of nonnative fishes should be considered

. A vigorous sampling program for adult razorback sucker in the lower Green River is needed
to document their abundance and distribution and the existence of spawning aggregations.

. Existing information on the biological and physical attributes of habitats presently used by
larval razorback sucker as nursery areas is insufficient for sound management of flows and
habitats to facilitate recovery. Studies addressing this need could incorporate aspects of the
planned NPS/LFL experiment on use of enclosures to study the growth and survival of
razorback sucker larvae, a mark-recapture approach, and(or) otolith aging of wild-caught
larvae.

. Resume sampling for razorback sucker larvae in the Colorado River inflow to Lake Powell.

. Methods for effective sampling of razorback sucker juveniles need to be developed.

vii