8192

• UCREFRP Catalog Number: 8192
• Author: Wydoski, D.
• Title: Review of Report Regarding Evaluation of Gravel-Pit Ponds.
• USFW Year: 1997.
• USFW - Doc Type: \
• Copyright Material: NO

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July 17, 1997

COLORADO RIVER fISHERY PRQJECr
GRANO JUNCTION, CO 81505

SWCA, InC.
172 W. 1275 S.
Logan, UT 84321

Mr. Frank K. Pfeifer, Project Leader
Colorado River Fishery Project
U.S. Fish and WIldlife Service
764 Horizon Driver, South Annex A
Grand Junction, CO 81506-3946

RE: Review of'~ative and Nonnative Fish Use of Two Gravel-Pit Ponds Connected to the
Upper Colorado River at 29 5/8 Road near Grand Junction, Colorado", by B.D. Burdick, 1. Flair,
M Lloyd, and B. Scheer.

Dear Frank,

I have reviewed the subject report .and have the following comments and suggestions.
First, I believe the report is a very valuable piece of work that has good practical application to
reducing the detrimental effects of nonnative fishes on native species in the Colorado River. As
. you know, I have a personal interest in this work because it addresses a hypothesis that I
fonnulated some 17 years ago when lwas with USFWS in Grand Junction. At the time, I spoke
to Com Construction and recommended that they recontour their gravel pits to slope toward the
river and thus drain with the descending limb of runoff. I'm glad to see that some aspects of this
are being addressed by your station.

This report reflects careful and meticulous work, and presents the data in clear and
understandable fashion. I strongly urge you to continue to test this idea with other gravel pits in
the area: Notice that the species common to these gravel pits are not numerous in other riverine
habitats, yet species like black bullheads, green sunfish, and largemouth bass are very effective
predators, even in small numbers. Reducing the availability of these refuges can have a positive
effect for native fishes by eliminating the source of these predators.

I reviewed the report thoroughly, and find no major problems in rationale or presentation.
Hence, I am not sending a marked copy of the report, but offer the following specific comments,
suggestions, or observations:

1. The occurrence of white suckers in the Colorado River in the Grand Junction area seems
higher than during the late 1970's and early 1980's. This seems to be one nonnative species that is
increasingly invading the system, with an equally volatile threat to predation--i.e., hybridization
with flannelmouth, bluehead, and possibly razorback suckers. Sucker populations of the Yampa
River near Craig, Colorado are significantly affected by this phenomenon~ i.e., most samples
contain complete morphologic intergradations between tlannelmouths, blueheads, and whites! It
might be wise to consider some genetic work on suckers in the area to begin to document genetic