WSP06858

• File Number: 8240.300.02
• Description: San Juan River Recovery Implementation Program - Recovery Plans & Information
• Basin: San Juan/Dolores
• Water Division: 7
• Date: 9/30/1994
• Author: San Juan Recovery Im
• Title: Long Range Implementation Plan - San Juan River Recovery Implementation Plan
• Water Supply Pro - Doc Type: Report/Study

DRAFT AND PREDECISIONAL DOCUMENT - FOR COORDINATION COMMmEE REVIEW ONLY

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4.4 DETERMINE ROLES OF NON-NATIVE FISH SPECIES IN THE
DECLINE OF NATIVE FISH SPECIES AND IMPLEMENT CORRECTIVE
ACTIONS.

In the Colorado River basin, non-native fish species have been implicated in the decline of the
native fish fauna. Past and ongoing studies have indicated that habitat alteration and concurrent
or subsequent introduction and establishment of non-native fish species result in depleted native
fish populations or their 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 industries. 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 Colorado squawfish and razorback sucker are sensitive to elevated levels of several
contaminants often found in the San Juan River. These results suggest additional studies to

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