7893

• UCREFRP Catalog Number: 7893
• Author: Satterfield, J. R., Jr.
• Title: Summary Of Responses, Colorado Division Of Wildlife Lake Management Plans.
• USFW Year: 1994.
• USFW - Doc Type: \
• Copyright Material: NO

(-). I,

Colorado Division of wildlife
December 1, 1994
Page 2

Potential for conflict with endangered species is high
in all but one of these stocking proposals. with the exception
of Harvey Gap reservoir, the Division does not and cannot
demonstrate that stocked fish will not escape into endangered
fish habitat. Thus, the Division's proposals hold potential for
conflict between endangered fish and the warmwater species it
wants to stock here.

If stocked nonnatives come into contact with endangered
fish or their habitat, the nonnatives will almost certainly harm
the endangered species. Colorado River n~tive fish evolved in a
largely predator-free system, ~ith Colorado squawfish the only
high-order predator. The comparatively recent introduction of
nonnative fishes is universally recognized as one of the key
causes of the decline of the native Colorado River fish fauna.
The native fish fauna is, quite simply, unable to compete with
the exotic species the Division proposes to introduce to the
system.

The five fish species the Division proposes to stock in
the northwest region pose a well-known threat to endangered
Colorado River fish. We briefly detail here documentation of
such problems by species:

1. Largemouth bass are repeat offenders when it comes to
predation on Colorado River endangered fish. Langhorst (1989),
Hendrickson and Brooks (1987), and Osmundson (1987) all report
largemouth bass predation on both razorback sucker and Colorado
squawfish. In fact, Osmundson (1987) reported that largemouth
bass actually prefer young Colorado squawfish to other species,
including red shiner and fathead minnow, when given a choice of
prey.

2. Blaok orappie predation on young Colorado squawfish in
floodplain grow-out ponds along the Colorado River was noted by
Osmundson (1989).

3. Channel oatfish were ranked as the number one problem
species with regard to impacts on native Colorado River basin
fish in a survey of expert government biologists by Hawkins and
Nesler (1991). Documentation of channel catfish predation on
endangered species iswidespread..___Channel catfish also pose a
threat to adult Colorado squawfish, as the dorsal spine can cause
catfish to lodge in the throat of and choke adult squawfish
(Pimental, et. al., 1985) ~ '

.
4. Bluagill were identified as competitors with endangered
species by expert government biologists surveyed by Hawkins and
Nesler (1991).