WSPC05696

• File Number: 8240.300.31.A
• Description: Colorado River Threatened-Endangered Species - Recovery Program - San Juan - Project Description
• State: CO
• Basin: San Juan/Dolores
• Water Division: 5
• Date: 2/1/1995
• Author: Unknown
• Title: San Juan River Basin - Recovery Implementation Program - Long Range Plans - February 1995
• Water Supply Pro - Doc Type: Report/Study

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extirpation. Negative impacts of non-native fishes include predation and
competition for limited resources (e.g., food and habitat). Studies to be
accomplished under this objective will enable the identification and implementation
of management actions to minimize or, if possible, eliminate adverse impacts of
non-native fishes on native fishes.

As with the native fish community, it is necessary to characterize the distribution
and abundance of non-native fish species. The identification of changes in the
resident fish community with emphasis on the occurrence of non-native fishes can
be related to other environmental changes for determination of cumulative effects.

Characterization of habitat use patterns of non-native fishes will determine the
degree of overlap with native fish species habitat requirements. Fish communities
in low velocity habitats are often numerically dominated by non-native species.
Studies will be conducted to characterize interactions among native and non-native
fishes in low-velocity habitats and to monitor responses of fish to flow mediated
habitat availability.

While it is difficult to directly identify or quantify competitive interactions, the
degree of commonality of food habits among native and non-native fishes can be
characterized. Similarly, direct predative impacts may be identified through studies
of food habits of non-native predators. Information from these studies will provide
insights on the role of non-native species in the dynamics of the native fish
community and need for measures to control non-natives.

The success in controlling non-native fish species will depend upon the variety and
intensity of methods used. Flow manipulations to mimic the natural hydrograph
and thereby diminish non-native fishes will not work alone. Management efforts
must also include more intense regulation of the sport- and baitfish activities.
Other methods, such as mechanical or piscicide removal may be implemented, if
feasible.

4.5. DETERMINE THE OCCURRENCE, EXTENT, AND ROLE(S) OF WATER
QUALITY DEGRADATION AND CONTAMINANTS IN THE DECLINE OF
NATIVE FISH SPECIES AND IDENTIFY AND IMPLEMENT
CORRECTIVE ACTIONS

The role of water quality degradation and contamination in the decline of native
fish species of the Colorado River basin is not well understood. Preliminary
research indicates that certain life stages of Coloradosquawfish and .razorback
sucker are sensitive to elevated levels of several contaminants often found in the
San Juan River. These results suggest additional studies to accurately characterize
the effects of various water quality parameters (singly, synergistically, or
antagonistically) are needed to improve management strategies for the endangered
fish species. Studies and management activities outlined under this objective will
address specific water quality impacts and necessry remedial actions.

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