6011

• UCREFRP Catalog Number: 6011
• Author: Miller, W. H., et al.
• Title: Colorado River Fisheries Investigations
• USFW Year: 1981.
• USFW - Doc Type: Preliminary Draft Report.
• Copyright Material: NO

to what haDDened in the
Colorado River Basin over 10 years
ago to the razorback sucker. Because it is a very long lived fish,
numbers would not drop immediately after habitat change. We believe
we are, witnessing in the Upper Colorado River the die off of the
old specimens with resultant drop in total population. Habitat changes
associated with this drop in razorback sucker population is not known.
The habitat needs of the razorback sucker need to be addressed in
the Upper Basin while there is still time to work with this species.
Flows and Key Species Habitat
To provide the needed habitat for the key fish species various
flows are needed at the proper time of the year. We are addressing the
question of providing needed flow for providing critical habitat by using
the FWS Instream Flow Methodology. We have established six IFG sites
on the Upper Colorado River, three on the Green and three on the main
Colorado, to assess needed habitat by life stage of the target fishes.
We have only conducted a few computer runs using this IFG data, and no runs
using the habitat preference data we have generated under this project.
What we have done this past year is develop the tools to use and the
means to handle the vast amount of data needed for relating flows to
fish habitat. We will start working with our field data on specific
habitat needs by flow requirements during the next few months. Examples
of habitat available vs. flow is given in Appendix D.
Recovery of the Target Species
Our project has documented the present distribution of the target
fishes. The final report will cover the flow needed to provide the
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