9410

• UCREFRP Catalog Number: 9410
• Author: Wydoski, R. S. and E. J. Wick.
• Title: Ecological Value of Floodplain Habitats to Razorback Suckers in the Upper Colorado River Basin.
• USFW Year: 1998.
• USFW - Doc Type: Denver.
• Copyright Material: NO

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juveniles. The use of such ponds would expose fish to waters that
provide olfaction cues in the event that imprinting behavior is
important. Exposure to feeding on natural food organisms may also be
important to survival after release into Upper Basin rivers. The average
size of razorback suckers at the end of the first growing season in the
Upper Basin is about 100 mm TL (- 4 in) and about 300 mm TL (- 12 in) at
the end of the second growing season in off-channel habitats. The best
survival of captive-reared razorback suckers in the Upper Basin has been
from larger stocked fish.

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It is highly recommended that razorback suckers be reared for two growing
seasons and stocked when they are about 300 mm TL (- 12 in) or larger.
Although augmentation stocking is not recovery, it provides a mechanism
to maintain adult razorback suckers in the Upper Basin until a solution
is found to achieve self-sustaining populations (i.e., recovery).

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Evaluate factors that may affect survival of razorback suckers after
stocking, including (1) use of floodplain ponds as a "half-way" habitat
where captive-reared razorback suckers can become conditioned to eating
natural food organisms before release, (2) importance of physical
conditioning to various water velocities prior to release, (3) size of
fish at release, (4) time of release, etc.

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If the provisions of (1) nursery habitat with adequate food and cover and
(2) adequate control of nonnative fishes cannot be achieved, human
intervention may be required to rear razorback suckers in predator-free
off-channel habitats so that their populations can be either
reestablished through reintroduction stocking or bolstered (i.e., jump-
started) through augmentation stocking.

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