7868

• UCREFRP Catalog Number: 7868
• Author: Kidd, G. T.
• Title: Endangered Fish Of The Upper Colorado River, Observations From 1970 Through 1995.
• USFW Year: 1996.
• USFW - Doc Type: \
• Copyright Material: NO

If the endangered fish populations are to recover, the pre-1975 conditions will probably need to
be duplicated and maintained. The existing conditions on the Colorado River do not provide
adequate spawning and rearing habitat. Despite numerous attempts to increase razorback sucker
populations through stocking, little or no improvement has been noted (Wydowski and Wick,
1994). Mr. Kidd attributes this to the fact the historic spawning and rearing habitat areas on the
Colorado River have been almost entirely eliminated. Razorback suckers appear to imprint on the
specific area of their origin (Wydowski and Wick, 1994). Lack of imprinting the stocked fish
may also account for the lack of success. Without suitable spawning and rearing habitat,
imprinting will not occur.
In order to enhance the likelihood of re-establishing the razorback suckers, the historic habitat
areas should be restored to a functional state. Without direct reconstruction and intensive
management of these areas, it is very unlikely that they will ever be functional for the fish.
Habitat recovery plans should include both:
1. Restoration and maintenance of spawning and rearing areas at least 5 acres in
surface area, 1500 to 2000 feet in length, with predominant water depths of 3 to 5
feet, and a water source other than the river itself, which provides a consistent flow
of warmer water.
2. Control of non-native fish through periodic draining, chemical control, and sorting
of desirable and undesirable species.
Without such measures, Mr. Kidd considers it unlikely that the endangered native fish of the
Upper Colorado River, especially the razorback sucker, will ever be able to recover to the point
of a stable, reproducing population.
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