7402

• UCREFRP Catalog Number: 7402
• Author: Nesler, T. P.
• Title: Aquatic Nongame Research, Endangered Fishes Investigations.
• USFW Year: 1989.
• USFW - Doc Type: Fort Collins, Colorado.
• Copyright Material: NO

1987-1988 Job Progress Report

State: Colorado

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Project No.: 02-01-035

Name: Aquatic Nongame Research

Study No. : SE-3-12

Title: Endangered Fishes Investigations

Period Covered: July 1. 1987 - October 31. 1988

Study Objective: To determine the impact of non-native, warmwater gamefish
species via predation and competition upon Upper Colorado
River Basin endangered fish species.

INTRODUCTION

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The introduction of non-native fish species in rivers of the Upper
Colorado River Basin is considered one of the primary contributing factors
toward the decline and endangered status of the Colorado squawfish
(Ptychochei1us 1ucius) , humpback chub (Gila cypha), bony tail (Gila e1egans),
and razorback sucker (Xyrauchen texanus). Gamefish species such as northern
pike (Esox 1ucius), channel catfish (Icta1urus punctatus), and largemouth bass
(MicroPterus sa1moides) are implicated as part of the exotic fish problem due
to their predatory nature, but field evidence documenting their presumed
negative impacts are lacking. Any future management plans to reduce the
populations of these gamefish species to benefit the endangered species,
however, will pose added difficulties due to their popularity with the angling
public. This study's primary focus is to determine life history patterns and
requirements of warmwater gamefish species in Upper Basin Rivers from the
perspective of how well these populations are adapting to the riverine
environment, and to compare and contrast seasonal habitat use and prey
selection between the endangered and non-native fishes for evidence of
potential impacts from predation and competition. Knowledge of limitations
imposed on these gamefish species and other introduced, non-native fish
species by a xeric riverine environment will help define the problems posed by
these species on the native fishes, and may also indicate recovery measures
necessary to minimize negative interactions with the endangered species.
The scope of this study as defined in the original Study Narrative (l987)
has been refined in study area and approach due to recent field experience.
Specifically, the standardized monitoring survey initiated as part of the

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