9408

• UCREFRP Catalog Number: 9408
• Author: Foster, D. K. and G. Mueller.
• Title: Movement Patterns, Behavior, and Habitat Use of Razorback Sucker Stocked Into the Green River at Canyonlands National Park, Utah.
• USFW Year: 1999.
• USFW - Doc Type: Open-File Report 99-107,
• Copyright Material: NO

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to preferred habitats, as well as higher rates of mortality (Pottinger and Pickering 1992)
and decreased fitness (Parkhurst and Dedual 1994).
Cleazly, fisheries biologists agree that efforts to minimize handling and transport stresses
generated during fish stocking is a worthwhile endeavor. The attachment of telemetry
transmitters requires surgery or attachment with anchors or sutures and can be very
stressful to the animal. Morton et al. (1995) determined that 17 of 18 species of African
mammals captured by physical restraint increased plasma cortisol concentrations as
compazed to normal, whereas capture using chemical sedatives usually caused a decrease
in cortisol levels. These findings illustrate the importance of employing MS-222 sedative
when outfitting fish with telemetry transmitters.
However, stressors to stocked fish do not ameliorate following stocking. Naive
hatchery-reazed fish will undoubtedly find that making the transition from hatchery pond
or raceway to turbid, swift rivers is a very stressful event. Stocked fish must learn to feed
upon natural food sources quickly, learn to identify and escape from predators, and
navigate lotic environments. Razorback suckers typically move long distances
downstream during the initial period following stocking, as well as experience reduction
in growth rates and condition factors (Hendrickson 1993, Ryden and Pfeifer 1995).
Based on our findings, it appears that this transition period is at least 2 weeks long.
This experiment has shown that pre-stocking acclimation is able to significantly alter the
dispersal rates of liberated razorback suckers, however a longer period of acclimation
appeazs to be needed for razorback suckers to remain neaz the release site. Perhaps a 2- to
4-week acclimation period is needed for razorback suckers to acclimate to their new
surroundings. This is based on experiments by Pottinger and Pickering (1992) that
showed that between 2 and 4 weeks is required for chronically confined (crowding and
infra-specific competition stresses) rainbow trout cortisol levels to decrease to those of
the controls.
CONCLUSIONS AND RECOMMENDATIONS
The collection of razorback sucker larvae from Middle Stillwater Canyon in 1993-1996
from the lower Green River (Muth et al. 1998) stimulated interest in this river section
(USFWS 1999). Unfortunately, the backwaters where larvae are typically collected are
ephemeral, flooding each spring for a few weeks before they drain with receding flood
flows. It's doubtful larvae gain any appreciable growth before either being forced back
to the main channel or stranded by receding flows. While nursery habitat is sparse,
historically, these river reaches must have been important migration corridors. However,
the appazent absence of both adults and juveniles may suggest these river reaches might
be only mazginally important to the species today.
Stocking within the boundaries of Canyonlands National Park is certainly a management
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