7400

• UCREFRP Catalog Number: 7400
• Author: Valdez, R. A.
• Title: The Endangered Fish of Cataract Canyon
• USFW Year: 1990.
• USFW - Doc Type: Final Report.
• Copyright Material: NO

PREFACE

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SUMMARY OF FINDINGS ................................................... vii

ABBREVIATIONS ............ -. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. xvi

ACKNOWLEDGEMENTS ........ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvii

1.0 INTRODUCTION .........................................,............. 1

1.1 Purpose and Objectives .............................................. 1

1.2 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1
1.3 Administration of the Study ............................................ 2

2.0 STUDY AREA ......................................................... 2

2. 1 Region 1: Green River above the Confluence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5
2.2 Region 2: Colorado River above the Confluence .. .. . .. .. .. .. .. .. .. .. .. .. .... 7
2.3 Region 3: Confluence to Brown Betty .................................... 9

2.4 Region 4: Cataract Canyon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 9

2.5 Region 5: Lake Powell Inflow ......................................... 12
2.6 River Flows and Water Temperatures .................................... 14

3.0 METHODOLOGy...................................................... 14

3.1 Basic Study Design. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 14

3.2 Data Collection and Storage ........................................... 18

3.3 Sampling Gear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 18

3.3.1 Electrofishing ................................................ 19

3.3.2 Gill and Trammel Nets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 20

3.3.3 Seines ..................................................... 20

3.3.4 Kick Screens ................................................ 20

3.3.5 Drift Nets ................................................... 20

3.4 Measurements of Gila Specimens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 21
3.5 Hatching Dates of YOY Colorado Squawfish ............................... 22

4.0 RESULTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 22

4.1 Summary of Fish Composition ......................................... 22
4.2 Fish Composition by Year ............................................ 24
4.2.1 Fish Composition in 1985 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 27
4.2.2 Fish Composition in 1986 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 27
4.2.3 Fish Composition in 1987 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 29
4.2.4 Fish Composition in 1988 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 29
4.2.5 Year Class Strength of Endemic and Non-Native Species ................. 29
4.3 Fish Composition by Region .......................................... 30
4.3.1 Region 1: Green River above the Confluence ......................... 33
4.3.2 Region 2: Colorado River above the Confluence ....................... 35
4.3.3 Region 3: Confluence to Brown Betty .............................. 35
4.3.4 Region 4: Cataract Canyon .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 36
4.3.5 Region 5: Lake Powell Inflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 36
4.3.6 Comparative Regional Densities of Native and Non-Native Species . . . . . . . . . .. 37

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