FWS/OBS-77/62 September 1977 an EVALUATION of the STATUS, LIFE HISTORY, and HABITAT REQUIREMENTS of ENDANGERED and THREATENED FI

FWS/OBS-77/62 September 1977

AN EVALUATION OF THE STATUS, LIFE HISTORY, AND HABITAT REQUIREMENTS OF ENDANGERED AND THREATENED FISHES OF THE UPPER COLORADO RIVER SYSTEM

By Timothy W. Joseph, Ph. D. James A. Sinning, M.S.

ECOLOGY CONSULTANTS, INC. 1716 Heath Parkway Fort Collins, Colorado 80526

Co-authors Robert J. Behnke, Ph. D. Colorado State University Paul B. Holden, Ph. D. Biowest

Western Water Allocation Project Funds Interagency Agreement Number Contract Number EPA-IAG-D7-E685 14-16-0009-77-012 Mr. Clinton Hall, Director Carl Armour, Project Officer Energy Coordination Staff Western Energy and Land Use Team Office of Energy, Minerals 2625 Redwing Road and Industry Fort Collins, Colorado 80526 Environmental Protection Agency Washington, D. C. 20460

This study was conducted as part of the Federal Interagency Energy/Enviromlntal Research and Development Program U.S. Environmental Protection Agency

Performed for

Western Energy and Land Use Team Office of Biological Services Fish and Wildlife Service U.S. DEPARTMENT OF THE INTERIOR TABLE OF CONTENTS

Page

PREFACE

ACKNOWLEDGEMENTS viii

INTRODUCTION 1

I. ABIOTIC COMPONENTS 7

Introduction 7 Annual Discharge 9 Depletions 9 Irrigation Use 11 Transmountain Exports 12 Reservoir Evaporation 14 Other Uses 17 Analyses of Historic Records 18 Salinity 28 Sediment 29 Temperature 32 pH 33 Dissolved Oxygen 34 Other Water Quality Parameters 35

II. BIOLOGICAL COMPONENTS 42

Introduction 42 Primary Producers 42 Invertebrates 44 Fishes 45

III. SPECIES DESCRIPTIONS 47

Introduction 47 Colorado Squawfish 54 Humpback Chub 61 Razorback Sucker 65 Bonytail Chub 70 Colorado River Cutthroat Trout 74 Kendall Warm Springs Dace 80 Roundtail Chub 82 Piute Sculpin 86 Mottled Sculpin 87 Flannelmouth Sucker 88 Mountain Whitefish 90 Speckled Dace 91 Mountain Sucker 92 Bluehead Sucker 93

iii IV. RIVER BASIN DESCRIPTIONS 94

Yampa River Basin 96 Green River Basin 103 White River Basin 111 Upper Colorado River Basin 116 San Juan River Basin 123 Dolores River Basin 129 Gunnison River Basin 132

V. MAJOR FACTORS INDUCING ENVIRONMENTAL CHANGE 137

Livestock Grazing 137 Parasites and Diseases 140 Dams 141 Introduced Fish Species 144 Hybridization 147 Industrial and Municipal Pollution 151 Logging 152 Water Depletions and Flow Requirements 154

VI. URGENT NEEDS AND RECOMMENDED RESEARCH PRIORITIES 156

LITERATURE CITED 163

APPENDIX A 174

iv LIST OF TABLES

Page

Table 1.1 Water Budget for the Upper Colorado River Basin, 1975 (Figures computed from U.S. Water Resources Council, 1976).

Table 1.2 Water uses by hydrologic subregions, 1975, Upper Colorado River.

Table 1.3 Main stem reservoirs of the Upper Colorado River Basin and their initial storage dates, contents for September, 1975 and annual evaporative losses for 1975 (U.S. Department of Interior, 1977: U.S. Geological Survey, 1975). LIST OF FIGURES

Figure 1.1 The upper Colorado River Basin and its three hydrologic subregions

Figure 1.2 Annual discharge and depletion of the upper Colo- rado River at Lee's Ferry, Arizona (Data from the Bureau of Reclamation, Salt Lake City, Utah, 1977.)

Figure 1.3 Water exported from the three hydrologic subregions of the upper Colorado River basin via transmountain diversions (1914-57) from Iorns, et al. 1965; the remainder from Upper Colorado Region State - Federal Inter-Agency Group, 1971; U.S. Water Resources Council, 1976.

Figure 1.4 Five year averages of monthly flow of the Yampa River at Maybell, Colorado, water years 1917 to 1974.

Figure 1.5 Five year averages of monthly flow of the White River at Watson, Utah, water years 1924-1977.

Figure 1.6 Five year averages of monthly flow of the San Juan River at Bluff, Utah, water years 1915-1977.

Figure 1.7 Five year averages of monthly flow of the Gunnison River at Grand Junction, Colorado, water years 1897- 1974.

Figure 1.8 Five year averages of monthly flow of the Colorado River at Cisco, Utah, water years 1914-1977.

Figure 1.9 Five year averages of monthly flow of the Green River at Green River, Utah, water years 1897-1977.

Figure 1.10 Five year average May depletions in four upper Colorado basin rivers.

vi PREFACE

The upper Colorado River system has become the focus of much concern. The presence of endemic species and their threatened and endangered status, coupled with a manifest pressure to reduce the already over-allocated water resources for additional agricultural, domestic, mining and industrial uses, and for the development of some of the largest fuel deposits (coal, oil, oil shale, uranium) in the United States, has produced a situation of potential conflict between development and environmental maintenance. There exists today a significant amount of information concerning many aspects of the upper Colorado River ecosystem. This large basin encompasses more than 109,000 square miles and has a unique resident fish population, for more than two-thirds of the native fish are endemic. This document represents part two of a more comprehensive three-part study of the status, life history, and habitat requirements of endangered and threatened fishes of the upper Colorado River system. The complete report consists of the following:

Part 1 - An Indexed, Annotated Bibliography of the Endangered and Threatened Fishes of the Upper Colorado River System.

Part 2 - An Evaluation of the Status, Life History, and Habitat Requirements of the Endangered and Threatened Fishes of the Upper Colorado River System.

Part 3 - Detailed Distribution Maps, Keyed to the Literature, of Endangered and Threatened Fishes of the Upper Colorado River System.

This report (part two) is an evaluation of the status, life history, and habitat requirements of the threatened and endangered fishes of the upper Colorado River system. The focus is, of course, the threatened and endangered fishes of the upper Colorado River system; and a full appreciation would not be possible without an adequate knowledge and familarity with the ecosystems in which they live and reproduce. This report attempts to present the total picture of both the endangered fishes and the upper Colorado River system. The report is organized vii into six major sections. A brief description of each section is presented below to enable the reader to move directly into those areas of particular interest.

Section I. Abiotic Components

Changes in water quantity and quality represent one of the major reasons for the population decline of many fish species. This section deals with physical and chemical aspects of the Colorado River system which directly affect the well being of its fishes.

Section II. Biological Components

This section represents a brief description of the biological components of the Colorado River, the role each plays in the environment, and their relationship to the important fishes.

Section III. Species description

This section presents a detailed discussion of the threatened and endangered fishes of the Colorado River as well as other important fishes of the system. Past and present distribution of each species and their life history are described in as much detail as the literature would allow. This section contains the most inclusive discussion of the fishes dealt with in the report. A discussion of speciation introduces the section.

Section IV. River Basin Descriptions

The focus of this section is on the major sub-basins that comprise the upper Colorado River drainage basin. The history and character of each basin are described in detail as is the distribution of fishes within each.

Section V. Major Factors Inducing Environmental Change

This section is a general discussion of those factors that have brought about declines or alterations in the population of the endemic fishes of the upper Colorado River system. Mechanics of their effects are discussed as well as the results.

Section VI. Urgent Needs and Recommended Research Priorities

This section summarizes what the authors feel are the important issues which need to be answered concerning the status of

viii endangered and threatened fishes of the upper Colorado River system. Areas which need to be mitigated are identified as are the recommended research methods.

This report represents the efforts of a number of individuals including known experts in the field of endangered and threatened fishes of the upper Colorado River system (see acknowledgments). It is important to note, however, that the contents of this report do not necessarily reflect a consensus of all authors and/or co-authors. It should also be mentioned that, because of the sensitive subject matter, this report is based on factual data whenever possible; due to the lack of a comprehensive data base and the limits placed on the existing literature, speculation and professional opinion represent a significant part of the conclusions. It is the feeling of the authors that without this speculation and professional judgment the report would be incomplete. Obviously the reliability of projections of future situations based on sometimes realistic, sometimes nebulous assumptions is always open to debate. A great degree of effort has been expended in trying to view each situation as realistically as possible and to avoid emotional or non-professional interpretations.

ix ACKNOWLEDGMENTS

We wish to acknowledge the contributions of those individuals who assisted in this study. Dr. Robert J. Behnke of Colorado State University provided his exceptional expertise concerning status and overall ecology of the warm and cold water fishes of the upper Colorado River system. Dr. Behnke also was instrumental in technical editing. Dr. Paul B. Holden was a key contributor in assessing the status of warm water fishes of this system. These individuals were instrumental to this study in providing insight and professional judgments; their contributions were critical. We also feel it is appropriate to extend our appreciation to the U. S. Department of the Interior, Office of Biological Services, Fish and Wildlife Service, Western Energy and Land Use Team, for identifying the need and allowing us to undertake such an important study, and particularly to Dr. Robert F. Raleigh for his guidance.

X INTRODUCTION

This study represents an evaluation of the present state of knowledge concerning the aquatic flora and fauna of the upper Colorado River basin. Relative detail of treatment varies according to the quantity and quality of available information, and all the information that would be desirable is not available for any particular subject area. Emphasis of the report is placed on the endangered and threatened fishes, their status, habitat requirements, and overall ecology. The upper Colorado basin comprises an area of approximately 109,580 square miles, encompassing all of the Colorado River drainage above Lee's Ferry, Arizona. Streams in this basin begin as clear, cold, first-order streams draining the mountains of Wyoming, Utah, and Colo- rado. They join to form larger streams that flow into the desert areas of southeastern Utah, western Colorado, and northern Arizona and New Mexico. In these regions they are large third- to fourth-order rivers that flow through some of the world's most spectacular canyons. The river system of the upper basin is geologically old and has taken millions of years to carve its way through thousands of feet of rock. Headwater streams typically flow over igneous and metamorphic rocks. Sedimentary rocks predominate in and below areas of second- or third-order streams and in some headwater regions. The aquatic fauna of this system are also very old, for they evolved in accord with the geological changes that took place in the basin. The indigenous native fish species of the system have been isolated from other drainages nearly as long as the present Colorado drainage has existed, and have largely evolved independently of fishes of other regions. This has resulted in a high degree of endemism in Colorado River fish species. Other aquatic flora and fauna have terrestrial dispersion mechanisms which have prevented the development of a high degree of endemism. The Colorado River basin has historically been a river of great fluctuations in flow, turbidities, and temperature. However, man- induced changes have dramatically influenced these regimes. Man's activities within the basin have increased sediment load and total dissolved solids (TDS). Man-made reservoirs in turn precipitate out this load, resulting in drastically reduced turbidities and flow, along

1 with strikingly altered temperatures in main channels downstream. In addition to the downstream impact, the accumulation of sediment in the reservoirs creates a definite problem regarding their life expectancy. The native fishes of the Colorado River basin evolved in, and are ideally suited to, the great flows and high turbidities of the system. Originally there were no large lakes in the basin; so the native fishes lack lacustrine adaptations. The appearance of large reservoirs and associated temperature alterations and reductions in flow and turbidity represented a severe negative impact to native fishes, while at the same time giving some introduced species a competitive advantage. To complete the picture, it is necessary to mention that the sediment load reaching the Gulf of California has been considerably reduced, resulting in dramatic changes in marine life and the loss of valuable fishery resources that were formerly dependent on the natural flows of the Colorado River into the Gulf of California. Land along the many rivers and tributary streams was extensively grazed as early as the mid-1800's. Extensive mining and prospecting with little or no consideration given to environmental effects also began at this time and have continued to the present. Additional impacts such as unsound forestry practices, channelization of streams for road construction and irrigation, water diversion out of the basin, coupled with the construction of large dams, have caused dramatic changes in the upper Colorado River basin habitat and have resulted in a decline in native fish populations. In addition, the introduction of exotic (non-native) fish species resulted in severe competition with the endemic species and has become a serious challenge to the continued survival of the endemic species. This report is an evaluation of the status, life history, and habitat requirements of the endangered and threatened fishes of the upper Colorado River system. It is essential that a picture of total system be reviewed if one expects to understand or appreciate the significance of the few species which are the focus of this report. In discussing the fishes of any river basin, we refer to resident Species as being native, endemic, exotic, and threatened or endangered. Presently there are 13 native, 7 endemic, at least 27 exotic and 6 threatened or endangered species in the upper Colorado River system.

2 Threatened or endangered species listed by the U.S. Department of Interior are starred. The other species are listed by the various states. They are as follows:

NATIVE COLORADO RIVER SPECIES

Colorado Cutthroat Salmo clarki pleuriticus Mountain Whitefish Prosopium williamsoni Roundtail Chub Gila robusta robusta Bonytail Chub Gila elegans Humpback Chub Gila cypha Colorado Squawfish Ptychocheilus lucius Speckled Dace Rhinichthys osculus yarrowi Kendall Warm Springs Dace Rhinichthys osculus thermalis Flannelmouth Sucker Catostomus latipinnis Bluehead Sucker Catostomus discobolus Mountain Sucker Catostomus platyrhynchus Humpback Sucker Xyrauchen texanus Mottled Sculpin Cottus bairdi Paiute Sculpin Cottus beldingi

ENDEMIC COLORADO RIVER SPECIES OR SUBSPECIES FOUND IN THE UPPER BASIN

Colorado Squawfish Ptychocheilus lucius Humpback Chub Gila cypha Bonytail Chub Gila elegans Flannelmouth Sucker Catostomus latipinnis Razorback Sucker Xyrauchen texanus Colorado Cutthroat Salmo clarki pleuriticus Round tail Chub Gila robusta robusta Kendall Warm Springs Dace Rhinichthys osculus thermalis

THREATENED OR ENDANGERED COLORADO RIVER FISH

*Colorado Squawfish Ptychocheilus lucius *Humpback Chub Gila cypha Bonytail Chub Gila elegans, Razorback Sucker Xyrauchen texanus Colorado Cutthroat Trout Salmo clarki pleuriticus Kendall Warm Springs Dace Rhinichthys osculus thermalis

EXOTIC COLORADO RIVER SPECIES

Rainbow Trout Salmo gairdneri Brown Trout Salmo trutta Brook Trout Salvelinus fontinalis Northern Pike Esox lucius Carp Cyprinus carpio Utah Chub Gila atraria

3 Red Shiner Notropis lutrensis Sand Shiner Notropis stramineus Fathead Minnow Pimephales promelas Redside Shiner Richardsonius balteatus Creek Chub Semotilus atromaculatus Longnose Sucker Catostomus catostomus White Sucker Catostomus commersoni Black Bullhead Ictalurus melas Channel catfish Ictalurus punctatus Rio Grande Killifish Fundulus zebrinus Mosquito Fish Gambusia affinis White Bass Morone chrysops Green Sunfish Lepomis cyanellus Bluegill Lepomis macrochirus Small Mouth Bass Micropterus dolomieui Large Mouth Bass Micropterus salmoides White Crappie Pomoxis annularis Black Crappie Pomoxis nigromaculatus Johnny Darter Etheostoma nigrum Yellow Perch Perca flavescens Walleye Stizostedion vitreum vitreum

The upper Colorado region is divided into three major river basins: the Green, Colorado, and San Juan (Figure 1). Each is divided into three major aquatic system types or zones: the cold-water high mountain streams, the large, warm, turbid rivers; and an intermediate zone which is geographically as well as physically, chemically, and biologically intermediate between the former two. For the purpose of this report, these three river types will be labeled upper zone (headwaters), intermediate zone, and lower zone (large river channels). The upper zone is generally regarded as "trout water," for the cold temperatures, clear water, and high gradient streams, with rocky or gravelly substrate, result in ideal habitat for these cold water fish. Primary production is significant and is primarily found in the periphytic algae. Benthic invertebrate production is substantial and represents an important food source for resident salmonids which dominate the fish population. As the stream flows from the upper zone into the intermediate zone, the water warms, flow becomes greater, and increased quantities of suspended and dissolved solids are added. The waters of this zone are generally clear except during spring runoff and after heavy rains. Substrates are generally rocky with occasional expanses of sand, especially in small and medium-sized streams. Benthic invertebrates are generally very abundant in the rocky areas and scarce in the sandy regions. Salmonids are less common, and cyprinids and

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0 24 Na 100 ILL IMI NILIN 00=1011=1111= . . . 11113 11T 'sr t ar ter 100: 107: 1010 The upper Colorado River Basin and its three hydrologic subregions. 5 catostomids tend to dominate the fish fauna. Primary production is highest in this zone because of higher nutrient levels and reduced turbulence. The lower zone has two distinct subunits: the canyon areas of steep gradient, and meandering river sections in flat terrain with canyons of low gradient. Water in this zone is generally warm and very turbid. Substrate types in steep gradient canyons alternate between sand and gravel rubble; in the level, meandering flats and low-gradient canyon areas, the substrate is almost totally sand. Primary production is virtually absent due to low water clarity and substrate scouring, and benthic invertebrate abundance is directly related to the availability of gravel-rubble substrate. The major energy source for aquatic communities in this zone is allochthonous materials. Fish species composition is generally similar in the two subunits; catostomids and cyprinids dominate, but relative abundance of the various species differs substantially.

6 I. ABIOTIC COMPONENTS

Introduction The upper Colorado River basin is a dynamic system with an ever- changing physical and chemical character. Snowmelt in the spring swells the many tributaries dramatically and adds large amounts of suspended and dissolved material. Summer rainstorms have a similar effect, but changes occur over relatively short periods of time. As a result, typical basin streams and rivers have widely variable flows and chemical characters as well as constantly shifting channel substrates. Man-induced changes have altered the physical and chemical characteristics of the upper basin. Some activities have enhanced the rate and magnitude of change while others have had a moderating effect. Ir- rigation practices, water exports, dam construction, unsound grazing and forestry practices, and municipal and industrial development have most affected the abiotic components of the system. Man's controlled use of water from the upper Colorado basin dates back to the horticultural practices of the Anasazi culture between the fifth and fourteenth centuries A.D. (La Rue 1916). The basin remained largely unexplored by modern man until the discovery of gold in 1859. Major John Wesley Powell's explorations in the 1860's introduced much of the basin to a new culture of man; and mining, farming, and ranching activities flourished in the basin around the turn of the century. Demands on the Colorado River water supply increased throughout the early 1900's as steadily increasing amounts of water were with- drawn for irrigation and domestic uses. Since 1963, the volume of water removed from the river has increased dramatically with expanding populations and for Colorado River water both from within and outside of the basin. The literature on water-related resources of the Colorado River is extensive. The most reliable and readily available water data are in the reports of the U.S. Geological Survey. Much of the early history of the river is documented in the earliest water-supply papers (La Rue 1916), some professional papers (Iorns et al. 1965) and more

7 recent water resources data, published annually. This information is well supplemented by works based largely on U.S. Geological Survey data by the Department of Interior (1977), the U.S. Water Resources Council (1976), the Utah Water Research Laboratory (1975), and the Upper Colo- rado Region State-Federal Inter-Agency Group (1971). Many other reports provide additional information on the water-related resources of the upper basin; however, a thorough review of the literature on abiotic components of the rivers in the upper basin is not within the scope of this evaluation report. The analysis of abiotic components in this report is intended to identify only those major changes in the upper basin that impact significantly on the fishery. General trends are emphasized, but studies of specific problems are also used to support the general character description. The objective of this analysis is to present an overview of the major changes in abiotic components in the upper basin and identify the causative factors. The abiotic components discussed in this report which may be of major consequence to the resident fishes of the upper basin include: water flow, salinity, sediment, temperature, pH, dissolved oxygen, and various other water quality parameters. The historic or virgin condition of each of these parameters is described in order to assess the magnitude of change. The causative factor behind each permutation will be identified whenever data or reliable professional speculation permit. Water data on the upper Colorado basin are presented in this report as traditionally considered according to three hydrologic subregions (Iorns et al. 1965): Green River, San Juan-Colorado, and Upper Main Stem (Figure 1.1). These subregions coincide closely to the 1401-1403 aggregated subareas (ASA) of region 14 as designated by the U.S. Water Resources Council (1976). The Green River Subregion consists entirely of the Green River drainage and encompasses the greatest area of the upper basin (44,744 mi2). The San Juan-Colorado Subregion is the drainage area 2 between the junction of the Green River and Lee's Ferry (38,644 mi ).

8 The Upper Main Stem (formerly the Grand Division) is the drainage area of the Colorado River above its junction with the Green River (26,192 mi2).

Annual Discharge Large yearly variations in flow occur in the Colorado River because of annual variations in precipitation and longer-term climatic changes. Man-induced depletions are having an increasing effect on flow variation. The average annual discharge (basin outflow) of the upper basin recorded at Lee's Ferry is 12,500,000 acre-feet for the 79-year period, 1896-1975 (Figure 1.2). A maximum of 22,000,000 acre-feet was estimated in water year 1907 and a minimum of 2,414,000 acre-feet was recorded in 1964. Discharge for 1975 was 11,288,300 acre-feet. Of the three hydrologic subregions, the largest volume of water comes from the upper Main Stem (about 50 percent in 1975). The Green River Subregion provides approximately 41 percent, and the San Juan- Colorado Subregion contributes the remainder. The major source of water is runoff from high, snow-laden mountains in the upper zone of the main stem. These high mountain areas comprise only .about 13 percent of the basin area but produce about 75 percent of the runoff (Upper Colorado Region State-Federal Inter- Agency Group 1971).

Depletions Annual discharge represents residual river flow, or the net volume of water remaining in the river after man-induced depletions (consumptive use and loss). River flow without these depletions has been computed since 1896 by the Bureau of Reclamation (Figure 1.2). This average annual undepleted (virgin) flow at Lee's Ferry for the 79- year period is estimated at 14,900,000 acre-feet. Depletions have increased from 250,000 acre-feet in 1896 to 1,800,000 acre-feet in 1914; 3,450,700 acre-feet in 1965; and 3,823,900 acre-feet in 1975. Water depletion can best be summarized by use of a water budget

9 COLORADO RIVER FLOW AT LEE'S FERRY, ARIZONA

STREAMFLOW IN MILLION 28 — ACRE FEET 26 — PER YEAR - -PROGRESSIVE 24 — 10—YEAR AVERAGE OF 22 — VIRGIN FLOW , pa' 'Et; AT END CF YEAR 20 —

18 — i

16 — n

14 —

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0 0 0 0 cs, 92 WATER YEAR

FIGURE 1.2 Annual discharge and depletion of the upper Colorado River at Lee's Ferry, Arizona (Data from the Bureau of Reclamation, Salt Lake City, Utah, 1977.) (Table 1.1). Approximately 95 million acre-feet of water is provided annually to the upper basin through precipitation. All but about 15 million acre-feet is lost to evapotranspiration; a part of the natural hydrologic cycle. Of the surface flow in the upper basin, about 3.82 million acre-feet is used by man. Irrigation, transmountain exports, reservoir evaporation and other uses (municipal, industrial, power generation, mineral extraction, livestock and stock-pond evaporation) account for 56, 19, 19 and 6 percent, respectively, of the total consumptive uses. The basin outflow (depleted flow) was nearly 11.3 million acre-feet in 1975.

Table 1.1 Water Budget for the Upper Colorado River Basin, 1975 (Figures computed from U.S. Water Resources Council, 1976)

acre-feet

Evapotranspiration ...... 79,887,800

Basin Outflow ...... 11,288,300

Irrigation Uses ...... 2,156,600

• Transmountain Exports ....711,000

Reservoir Evaporation ....741,200

Other Uses ....215,100

Total ...... 95,000,000

Irrigation Use The consumptive use of irrigation water is that volume lost to soil evaporation and plant uptake and evapotranspiration. Incidental loss also occurs such as evaporation from canals and associated reservoirs. Much of the water used for irrigation returns to the river through surface and groundwater flow and is not considered consumed or lost but is generally considerably altered in quality. Irrigation and associated water use during 1975 accounted for about 56 percent of the total depletion of water in the upper basin. About 1.6 million acres of land are presently under irrigation, with

11 most of these lands lying in the intermediate and lower zones of the basin. Most of the readily available sources of irrigation water were developed between 1850 and 1900 by private individuals and small irrigation companies. The practice of diverting water for crops began in the high, fertile valleys fed by small streams and rivers. Flow was easily managed, and diversion dams were built on many small streams. The water was transported via man-made canals to adjacent pasture and farm land. In recent years, larger and more elaborate irrigation projects have been constructed, and much larger quantities of water are now diverted from the streams in the basin. The average annual irrigation consumptive use for the period 1914-57 was 1,769,100 acre-feet (Iorns et al. 1965). Average use in the five-year period from 1971 to 1975 increased to 2,188,000 acre- feet (Bureau of Reclamation 1977). Several times this amount is diverted from the streams, applied to the land, and, except for the amount used consumptively, is returned to the stream. Approximately 43 percent of the irrigation water consumed in the upper basin is used in the Upper Main Stem Subregion. A nearly equal amount is used in the Green River Subregion (39 percent) and only 18 percent is used in the San Juan-Colorado Subregion. The importance of water for irrigation is further demonstrated when water use in each subregion is considered (Table 1.2). Seventy- three percent of the water depleted by man from the Green River Sub- region and 62 percent of that depleted from the Upper Main Stem is used for irrigation. The proportion of water depleted by irrigation practices in the San Juan-Colorado Subregion (33 percent) is surpassed by reservoir evaporation (52 percent).

Transmountain Exports Water exported from the upper basin is carried by tunnels, canals, and aqueducts through or across watershed divides. These diversions usually originate in the high mountain streams and small rivers where water quality is high. Evaporative losses from small

12 Table 1.2 Water uses by hydrologic subregions, 1975, Upper Colorado River

DEPLETIONS IN ACRE-FEET TYPE OF USE GREEN RIVER UPPER MAIN STEM SAN JUAN-COLORADO REGION TOTAL

ACRE ACRE % ACRE ACRE FEET FEET FEET FEET Irrigation Consumptive Use 834,241 (73) 938,414 (62) 383,945 (33) 2,156,600 (56)

Transmountain Exports 117,518 (10) 501,726 (33) 91,756 (8) 711,000 (19) Reservoir Evaporation 1--. 88,380 (8) 48,055 (3) 604,765 (52) 741,200 (19) Lo Minerals 30,244 (3) 10,081 (1) 10,529 (1) 50,854 (1) 4 Steam-Electric 30,244 (3) 1,120 ( 1) 54,887 (5) 86,251 (3) Domestic, Commercial, 13,442 (1) 17,922 (1) 12,770 (1) 44,134 (1) Institutional Use

Miscellaneous Use 24,841 (2) 4,678 (41) 4,342 (41) 33,861 (1)

Total 1,138,910 (100) 1,521,996 (100) 1,162,994 (100) 3,823,900 (100) reservoirs associated with these diversions are included in export figures. Exports during 1975 accounted for about 19 percent of total water loss (Table 1.2). Perhaps the oldest diversions in the upper Colorado River basin are those associated with the Strawberry Project in northeastern Utah (La Rue 1916). Water was first diverted from the Strawberry River to Hobble Creek in 1893. This diversion is still in operation. Variation in the volume of water exported is large; however, the net increase has been dramatic since 1953 (Figure 1.3). Water exported from the upper basin remained under 150,000 acre-feet until 1938. By 1957, 42 transmountain diversions were exporting about 468,400 acre-feet. Water exports in 1971 totaled 583,000 acre-feet and then rose to 711,000 acre- feet in 1975. Except for the period between 1914 and 1935, exports from the Upper Main Stem have greatly exceeded those of the other subregions (Figure 1.3). In 1975, transmountain exports accounted for 33 percent of the water consumed in the Upper Main Stem Subregion, and only 10 percent and eight percent of the water used in the Green River and San Juan-Colo- rado Subregions, respectively (Table 1.2). Water diverted from the upper Colorado River basin is used in the Great Basin, Arkansas River basin, Platte River basin, and Rio Grande basin. One small diversion in southern Utah imports about 2,600 acre- feet of water annually from the East Fork of the Sevier River into the upper Colorado River basin.

Reservoir Evaporation The volume of water lost from the upper basin as a result of evaporation from large surface reservoirs has been computed only for the large main stem impoundments. The majority of these reservoirs were formed as a result of the Colorado River Storage Project, authorized by Congress on April 11, 1956. This included construction of six large dams (Table 1.3), most of which were impounding water by 1964 (U.S. Department of Interior 1977). A storage capacity of 33,439,000 acre-feet was developed by 1965, including Lake Powell on the Colorado River, Flaming Gorge and Fontenelle Reservoirs on the Green River, Navajo Reservoir on the San Juan River,

14 1000acre feet 800 1914 Figure 1.3Waterexported fromthethreehydrologicsubregionsof theupperColoradoRiverbasinvia 1920 Region State-Federal Inter-AgencyGroup,1971;U.S.WaterResources Council,1976, transmountain diversions (1914-57)from rl San Upper ColoradoMainStem Green River 1930 Juan,Colorado 1940 Iorns, etal.1965;theremainder fromUpperColorado 1950 1960 1970 1975 Table 1.3 Main stem reservoirs of the Upper Colorado River Basin and their initial storage dates, contents for September, 1975 and annual evaporative losses for 1975 (U.S. Department of Interior, 1977; U.S. Geological Survey, 1975).

RESERVOIR STORAGE BEGAN CONTENT (9/75) ANNUAL EVAPORATION (acre-feet) (acre-feet)

Blue Mesa 10/26/65 695,000 7,000

Flaming Gorge 11/ 1/62 3,650,000 79,000

Fontenelle 4/ 1/64 329,000 20,000

Lake Powell 3/13/63 20,452,000 519,000

Morrow Point 1/24/68 116,000 2,000

Navajo 6/27/62 1,392,000 30,000

657,000

16 and Blue Mesa Reservoir on the Gunnison River. The development of Morrow Point Reservoir on the Gunnison River in 1968 added 117,000 acre-feet of storage. Evaporation from the aforementioned reservoirs during 1965 was approximately 648,000 acre-feet (Upper Colorado Region State-Federal Inter-Agency Group 1971). Between 1971 and 1975, main stem regulating reservoirs recorded an increase of 10,156,000 acre-feet of storage (Bureau of Recla- mation 1977). Reservoir evaporation rose to 741,200 acre-feet in 1975 with the six major reservoirs (Table 1.3) responsible for an estimated 89 percent of the loss (Bureau of Reclamation 1977). Loss of water to reservoir evaporation accounted for over 19 percent of the 3.82 million acre-feet of water depleted by man in the upper basin in 1975. Nearly 82 percent of the reservoir evaporation comes from the San Juan-Colorado Subregion. This loss principally from Lake Powell although losses from Navajo Reservoir in New Mexico are also high when compared to its surface area. Over half of the water used in the San Juan- Colorado Subregion is lost to evaporation (Table 1.2). Evaporative loss from the four other main stem reservoirs tends to be less because of smaller surface areas, cooler waters, and a cooler climate at higher elevations. Only eight percent and three percent of the water consumed in the Green River and Upper Main Stem Subregions, respectively, are lost to evaporation.

Other Uses Uses of water other than irrigation, exports, and evaporation, account for a relatively small percentage of the total volume depleted by man. These uses include municipal and industrial needs, electrical power generation, mineral extraction, livestock needs, and stock-pond evaporation. The discovery of gold and silver initiated the development of the upper basin (La Rue 1916). In 1859, gold was discovered in Breckenridge, Colorado, and soon mining camps were commonplace. Many miners, diasppointed in their search for precious minerals, turned to ranchfng or farming. This settlement brought about dramatic increases in population and water use; by 1940, the population of the upper basin had increased to nearly 275,000. In 1957, the average annual volume of water for domestic and industrial use was 22,600 acre-feet, or about one percent of the total consumptive use at that time (Iorns et al. 1965). In the late 1950's, the demand for water grew with the increase in steam-electric power production. Coupled to an increasing population (nearly 300,000 in 1950) and gas and oil extraction, water use increased to 132,000 acre-feet in 1965 (Upper Colorado Region State-Federal Inter-Agency Group 1971). By 1975, substantial population increases (estimate of 431,400) and industrial development in the upper basin increased water use to 215,000 acre-feet or six percent of the total consumption by man. The greatest volume of water used in the upper basin for municipal and industrial reasons is in the Green River Subregion, where mineral extraction and steam-electric generation demands are greatest. Use is also high in the San Juan-Colorado Subregion where steam-electric generation consumes about five percent of the total (Table 1.2).

Analyses of Historic Records Man-induced changes in flow of the upper Colorado River have resulted in manifest changes in water quality and fish habitat. Water depletions and augmentations have affected the littoral areas, pool-riffle proportions, streambed scouring, temperature, and sedimentation. Habitat alterations are difficult to measure, but changes in flow and water quality can be quantified and used as an index to h,;.bitat quality. This information is adequate for establishing general trends, but is not sufficiently specific for use in correlations with biological changes in the upper basin. For example, depletions occur primarily during the irrigation season (April- September), and much less water withdrawal occurs during the winter. De- pletions during the warm months are proportionately greater than those shown on yearly summaries (Figure 1.2) because the large fluctuations during summer are averaged over the whole year. Also, depletions vary from basin to basin, and summaries are not specific enough to show these differences. Historic recorded flows of six major rivers in the upper basin were examined to evaluate trends in water depletion and augmentation. Data for these evaluations were recorded by the U.S. Geological Survey and were retrieved from magnetic tape storage in the National Water Storage and Retrieval System files. The period of record varies between stations, but most data are continuous from before 1920 to the present. The stations examined were: o Colorado River near Cisco, Utah o Green River near Green River, Utah o Gunnison River near Grand Junction, Colorado o San Juan River near Bluff, Utah o White River near Watson, Utah o Yampa River near Maybell, Colorado Two of these stations (the Green River near Green River, Utah, and the Gunnison River near Grand Junction, Colorado) provide continuous flow data from 1897. Five-year averages of flows recorded during the months of May (spring runoff) and November (minimum withdrawal at low flow) were plotted to illustrate historical trends (Figures 1.4, 1.5, 1.6, 1.7, 1.8, 1.9). Five- year averages were used to reduce point scatter resulting from short-term climatic variations. Calculated virgin flows were provided by the Bureau of Reclamation, Salt Lake City, Utah, and were plotted on the same graphs to illustrate changes caused by man's activities. Some of the virgin flow values for the period prior to 1920 are lower than the recorded flows, and it is apparent that either the computed virgin flows or the recorded flows are incorrect. Therefore, trends prior to 1920 are not used in the discussion which follows. The six rivers studied exhibit different degrees of flow alteration. The Yampa and White Rivers show little variation from virgin flows, indicating few depletions (Figures 1.4 and 1.5). Relatively small amounts of land are irrigated in these two basins; little industrial development, and no major dams, exist on either the White or Yampa Rivers. Small reservoirs on the White River have little apparent effect on flow. Deple- tions have not increased significantly during the period of record, which indicates that little additional irrigated acreage has been added since. 1920. The White River shows more depletio-s in May than the Yampa, suggesting it supports a larger agricultural community.

19 SIATICIN I 0251000

•...... • •.... sobotro.n0000 • 4 • 1 1

assaus.n0000 • /

606632.00000 • A.

356223.00000 • May- 1

503624.00000 •

1 1

FEET) 1

- 253020.00600 • •

(ACRE Virgin flow ... 20241h.00000 • Actual flow 1

M612.00000

1 10t206.00000 4 1 1 1 1 S0600.00000 • 1 1 1 November t • 0.00000 • • • • • ...... 4 ...... •...... • tgeo 111 011 4 1900 tato 1420 : 1 430 1 40 1950 19b0 1 970 1920 FIGURE 1.4 Five year averages of monthly flow of the Yampa River at Maybell, Colorado, water years 1917 to 1g74. years 19i: 0 1(174.

11/47104 1 9146500

* • • • • ...... 1 99194.44000 + 1 1 1

129919.60000 •

11599 3.20000 * MAY

1 1

FEET) 1 - 1 1 1 (ACRE

Virgin flow Actual floe

1 - 1 x---/V _—...mr,.05 28117001 000o • • *II NOVEMBER ,, 1 'I 1 • 1 X '1 1 I 19635.90000 • 4 o.1 I 1 1 1 6 I 1 ) I 1 0.00000 • . • .... 4 .... • .... * .... • ...... • .... + .... + .... + .... • 18 04 0 . iano 1 Q10 1 910 1 920 1930 1940 1 950 1 960 1970 1980

FIGURE 1.5 Five year averages of monthly flow of the White River at Watson, Utah, water years 1924-1977 zz(ACRE - FEET) STATION 5514124010O itz336.n0000 1 490141,00000 36,60 20072.00oon 426876.00000 612660.90000 304140.00000 61261100000 3S011.40000 N 0

6.0 00000 : 011

00 o37uson ".2 , el 1SA0 a teI ' • •

• • • •

I . • . . I I i . 1 1 I 1 i I 1 1 i i 1 1 1 1 1 i i i i 1 I I I I I I I I 1 1 I

. . FIGURE 1.6 Five yearaveragesof monthlyflowofthe San JuanRiveratBluff, Utah,water Actual flow Virgin flow 1 A00 • . years 1915-1977. 1 g00 • • ...... 19 10 NO + • ...... VEMBER )I-.. 19?0 1------vt /

. MAY

/ --. . ! 4 ...... / ...... A

‘ \

I I . 030 • 1 1 ■

4 N

I ......

i / —

1990 , • 4. N

.. 1 i

A /•, ‘\ 11 ..... 1 ‘ \I \k• \\ 1950 1 I •

...... / 1960 1 • 4

...... i 1 / / ,:' i 1970 *----- / 4

4 /

-- ...... 1960 .

• • 4

I • • 4 1 1 I • I i + I I I 1 1 I I + 1 4 I I 1 1 i 1 I I I I I 1 1 1 1 1 1 1 1 i I I I I I

STArION, s 9152F00

• • • • ...... • • • ...... • 846900.00000 • 1 I \ , \ 1 762210.00000 • •

1 1 775 0 000 • 6 2 .00 /s. 1 1 1 / ■ 1 1 1 \, 1 592830.00000 • 1 • 4C I / Spelso.nonoo May I / 1 II

feet) 1

- 423480.00000 + 1 1 1 1 (acre 358760.00000 • 1 EZ Virgin flow - - 1 Actual flow 1 00 256070.000 1 1 0

106380.00000 • 1 1

1 e 440 90.ft0000 • November - 4--- - - > /- + ii I ._,_-. ---.... .4------r- ---=r>„. .„.....-2_.7;. 4 Y• I - I 1 1 ---K.----- ' 3Y I

0.00000 • a • ... • ... • ... a ... • ... • ... * ... + ... 4, ...... 4 ...... • 1090 lego 190n 1 010 1920 1 930 1940 1 950 1960 1970 1980 FIGURE 1.7 Five year averages of monthly flow of the Gunnison River at Grand Junction, Colorado, water years 1897-1974. •

STATION 9180500

e ...... * ...... + ...... * + 2080000.0nnno . + I \ el 1 I I I 1 I I I I 1 I 1 I 1872000.00000 4 / 1 / ■%\ I I\ 1 1

1 / 1 / \ e 166800000000 • 1 / 1 / I \. 1 / I / \ I / ‘, i i I I . t / I \ / i / 1 / I 1856000.00000 • / / . I / 1 I / I 1 /‘•. / I / I / \ i 1 / I 4E- I 1 \ I 1 / 1 I 1 / \ /' / \ / + 1288000.00000 • .V i May ■ / 1 1 I 1 , 1 I lOancoo.aapoo • 4.

-FEET) i I I 1 I i 1

(ACRE i 1 83200000000 e e ts.) i z- I I Vi rgin flow I I Actual flow I I I 624000.00000 t + I i I I I 1 I 1 416000.0000 n e e I I 1 November yl .,, ,:-.... ._ —...._ I 208000.00000 ," ---=-:..-..- — e 11,11 1 -- i i 41• 1 VHZ i 0.00000 e • • ... e ...... e ...... e ...... e ...... a ...... •...... e ...... e lahn 1890 1900 1910 1920 030 1 980 1 950 1960 1970 1980 FIGURE 1.8 Five year averages of monthly flow of the Colorado River at Cisco, Utah, water years 1914-1977.

, 4 ' 011. • years 1914-1917. ME:tft4;.:: ' 14

ST MON s V315400

...... • ...... 4 ...... 4 ..... 4.4 44 ...... • ...... • ...... • 14a n000.44400 • • . / i /1 % ‘. 1 1 Ii. \ t 1 . 13 3207200000 • .\ / \ 1 A 1 A 1 1 \ 1 I -, / i t l tleaclea.00n00 • A i . , / \ 1 / I / \ 1 1 1 i \v / . \ / 1 A 1 1036056.00000 . 1 4\ / 1 1 ' \ .,' 1 i ./ ..' I ! May 1 008044.00000 • I I/ 'si • I 11 iii 1 ...... 4.1 I \ 1 a) i 1 4/ \ I 4-1 I 111 V1004100000 • 4 i I I \, i4w o 1 I O I 1 ....0 I 1 S92432010000 • • ts.3 1 Virgin flow ------I I-" I Actual flow 1 1 1 1 1 404424.00000 • 4 1 1 i 1 1 1 J 1 29601 4.00001 . • 1 .A.t .,•___-___,___...... 1 1.1 I II 1 --- 4---.----4.---+ --, 1 -, . --•----.---*--___ • 1418008 4 00000 • '--.---- — - — ..--• /..-----. ..., 1 4------4--- November -=-1- --- 1 li i 1 6. 1 1 1. 1 1 0.400011 • . • •...... 4 ...... + ...... + ...... + ...... 4 ...... •...... + ...... 11180 IA0fl loon 1410 192o 1930 1940 1950 1960 1970 1940 ' FIGURE 1.9 Five year averages of monthly flow of the Green River at Green River, Utah, water years 1897-1977. The other four rivers exhibit substantial depletions during May (Fig- ures 1.6, 1.7, 1.8, 1.9), and are more clearly quantified in Figure 1.10. The general May pattern is similar; depletions are relatively constant during the period of record until the 1960's when they increase dramatically. The preceding discussion of depletion components pointed out that irrigation and transmountain diversions, the major portion of upper basin depletions (Table 1.2), did not increase greatly prior to the 1960's. The dramatic increase in May depletions during the 1960's is correlated with the completion of the large Colorado Storage Project dams (Table 1.3). These main stem dams impound the high spring flows, thus causing additional May depletions. This recent reduction in high flow is most dramatic in the San Juan River where depletions increased four to five- fold (Figure 1.10) after Navajo Dam was completed. The reductions in the Colorado River at Cisco and the Gunnison River at Grand Junction are due largely to the Curecanti Dams on the Gunnison. Flow in the Green River is influenced by Flaming Gorge Dam but ameliorated considerably by tributaries such as the Yampa, Duchesne, and White Rivers. A significant pattern is apparent in May flows after 1960 in the Colorado, Gunnison, and San Juan Rivers (Figures 1.6, 1.7, 1.8, and 1.10). May flows have reached record lows in these areas, and are now below even the low flows of the 1930's. This means that the present high water flow is lower than at any time in recorded history, and that the high flows needed for scour and channel maintenance by the river no longer occur. Flows in the lower Green River (Figure 1.9) have not dropped below those of the 1930's primarily because of the unimpounded inflow of the Yampa and White Rivers. November flows also have been altered in the rivers impounded by large dams. Tailwater augmentation from winter reservoir drawdown has resulted in November flows that exceed previous recorded November highs except in the Colorado River near Cisco, Utah (Figures 1.6, 1.7, 1.8 and 1.9). Prior to the impact of the dams, recorded and virgin flows were nearly the same, indicating very little depletion or augmentation in November. These data, in conjunction with those showing high May depletions, support _72 the evidence that agricultural uses dominate upper basin depletions.

26 500,000 400,000

300,000 200,000

100,000 0 1910 1920 1930 1940 1950 1960 1970 1915 1925 1935 1945 1955 1965 1975 700,000 Green River at Green River, Utah 600,000

••••■■•■ 500,000

400,000

300,000

200,000

100,000 0 1910 1920 1930 1940 1950 1960 1970 1915 1925 1935 1945 1955 1965 1975 FEET)

- Colorado River at Cisco, Utah

(ACRE 400,000

300,000

200,000

100,000 -- 0 1 1 1 1 1910 1920 1930 1940 1950 1960 1970 1915 1925 1935 1945 1955 1965 1975 400,000 San Juan River at Bluff, Utah 300,000

200,000

100,000 0 HI 1910 1920 1930 1940 1950 1960 1970 1915 1925 1935 1945 1955 1965 1975 Gunnison River at Grand Junction, Colorado

FIGURE 1.10 Five year average May depletions in four upper Colorado basin rivers. 27 The general pattern of dam releases, and their regulation of stream flows in the Colorado basin, has been presented by several authors (Vanicek, Kramer, Franklin 1970, Mullan et al. 1976). In an effort to fully appreciate the effect of depletions, monthly values (May and November) were used as opposed to annual or seasonal averages.

Salinity One of the notable changes in water quality resulting from man's use of water in the upper Colorado River is the increase in salinity (total dissolved solids or TDS). For this reason, it is one of the most significant economic problems facing water users. Because of its effect on crops, it has been estimated that each milligram per liter (mg/1) increase in salinity at Imperial Valley, California increases costs to water users by $230,000 annually (Kleinman et al. 1974). Generally, salinity increases at each succeeding downstream zone as a result of evaporation and leaching caused by diversions, stream and reservoir evaporation, and municipal and industrial uses. Salinities are further increased by evapotranspiration of phreatophytes, and salt input from inf lowing mineral springs and saline streams. Solution of salts from streambeds and reservoir basins also adds to the total TDS. Natural and man-related sources of salinity are difficult to segre- gate since irrigation practices preceded water quality records. The principal contribution of salts is from diffused and natural point sources. In the case of natural diffused sources, salt pickup occurs over large areas of surface and underlying soils. These sources contribute the largest overall proportion of the salts in the waters of the Colorado River and are the most difficult to measure (Crawford and Peterson 1974; Utah Water Research Laboratory 1975; U.S. Department of Interior 1977; Wentz 1974). Areas of significant natural diffused sources of salinity include the lower Green River, the Grand Valley, the Uncompahgre and Gunnison Rivers, and McElmo Creek areas in Colorado, Price and Uintah River basins in Utah, and the Big Sandy River basin in Wyoming.

28 Natural point sources are primarily mineral springs from which the salinity contribution is easily. identified. These major natural point sources of salinity are the Dotsero and Glenwood Springs as well as a salt anticline in the Paradox Valley of the Dolores River. These sources are presently monitored and controls have been proposed. (U.S. Department of Interior 1977). Salinity at Lee's Ferry has generally increased since 1941. In this area, the relationship between total dissolved solids concentration and flow is evident. During the period of record, salinity was highest in 1954, 1963, and 1964 when flows were lowest. Increases in salinity during those periods were caused by man's activities in the upper basin as well as climate induced variations in flow. The construction of Glen Canyon Dam and the filling of Lake Powell brought about significant increases in salinity at Lee's Ferry. During the first year of storage in 1963, the flow at Lee's Ferry was reduced to 1,384,000 acre-feet with a mean TDS of 934 mg/l. Reduced flow and leaching of salts from the newly formed lake basin are believed to be primarily responsible for this increase. The average concentration for 1971-72 period was 559 mg/1 (U.S. Department of Interior 1977). Although the effect of irrigation on salinity of the upper basin is not yet fully quantified, it is generally accepted that 2.0 tons of dissolved solids are picked up from every acre of newly irrigated land. This is accompanied by an additional depletion of 1.5 acre-feet of water per newly irrigated acre (U.S. Department of Interior 1977; Utah Water Research Laboratory 1975). In addition to irrigation and reservoir storage, it is known that transmountain exports have a significant effect on salinity. Since most exports occur in the upper zone where salinity is generally low (<100 mg/1), the dilution potential for the more saline waters of the lower basin is reduced. Historic flows have been most significantly affected by exports since 1941 with diversions of the Colorado-Big Thompson Project, Duchesne Tunnel of Provo River Project, Roberts Tunnel by the City of Denver, and a number of smaller diversions.

29 Evaporation from large main stem reservoirs became a significant contributor to increasing salinity in the mid-1960's with the completion of Glen Canyon Dam, Navajo Dam, Flaming Gorge Dam, and the Seedskadi (Fontenelle) and Curecanti Units (Blue Mesa and Morrow Point). Approximately 48 percent of the total dissolved solids of the upper basin comes from the Upper Main Stem Subregion. About 33 and 19 percent of TDS come from the Green River and San Juan-Colorado Subregions, respectively (Iorns et al. 1965). TDS varies inversely with flow, but the total salt load tends to vary directly with flow. Thus, more tons of salts are transported by the river during high flow than during low flow, although the concentration is less.

Sediment The nature of the sediment load in the upper basin is inherent in the character of the watershed and the geology of the region. Streams in the mountainous zone of the upper Colorado basin flow over primarily crystalline rocks of igneous and metamorphic origin such as granites, gneisses, schists, quartzites, and argillites, which are generally resistant to dissolution. For this reason, water in the high mountain streams is generally low in dissolved materials. Suspended materials are also low except during high runoff periods. Underlying much of the lower mountain slopes and foothills are vast expanses of sedimentary rock. These are mainly alternating beds of resistant sandstone and soft marine shales, such as the Mancos shale formation or Mississippian and younger age limestones. Valleys underlain by soft shales with sandstone or limestone cliffs along the margins are a characteristic land form in this zone. Erosion in these areas produces both high sediment and dissolved solids yields. About 75 percent of the lower zone is overlain with young unconsoli- dated deposits of alluvial, colluvial, glacial, and eolian origin, although in most places it is only a few feet thick. This material becomes easily suspended and enormous quantities of sediment are transported to the river during rainstorms.

30 Sediment in the rivers of the upper basin is believed to have increased riramatically by the early 1900's, along with the mining, grazing, irrigation and timber practices of man. In 1957, the suspended sediment load at Lee's Ferry was greatest at 143 million tons when flow was greatest at nearly 19 million acre-feet. Low sediment levels were observed in 1954 when flow was also low. Sediment loads underwent additional changes as a result of man's influence on the rivers. Total sediment load decreased substantially due to the construction of large dams. Fontenelle, Flaming Gorge, Blue Mesa, Morrow Point, Navajo, and Glen Canyon Dams have produced dramatic reductions in the sediment load in the upper basin in recent years. These changes began in 1959 when the coffer dam used in the construction of Glen Canyon Dam trapped sediment and reduced the annual load at Lee's Ferry to about 20 million tons. The annual sediment load increased in 1962 to 67 million tons when the coffer dam filled, and dropped to 2.2 million tons in 1963 with the closure of Glen Canyon Dam. Lake Powell and Navajo, Fontenelle, Falming Gorge, Blue Mesa, and Morrow Point Reservoirs now trap about 75-80 percent of the sediment of the upper basin that normally flowed into Lake Mead. The river immediately below these dams has changed from turbid to relatively clear (U.S. Department of Interior 1977). Some causative factors for high sediment in the upper basin, particularly in the late 1800's and early 1900's, are believed to be overgrazing, poor irrigation practices, and poor timber management. Incidental activities may also be responsible for increased sedimentation. In the upper Strawberry Valley of eastern Utah, private land- owners apply defoliants and herbicides to streamside willows to reduce water loss in areas used for livestock grazing. Destruction of this vegetation reduces the root system and thus the stability of the stream bank. Of the total average annual sediment load at Lee's Ferry for the years 1914-1957, about 20 percent was derived from the upper Main Stem Subregion, 27 percent from the Green River Subregion, and 53 percent from the San Juan-Colorado Subregion. About 38 percent of the total

31 load came from the San Juan drainage alone (Upper Colorado Region State- Federal Inter-Agency Group 1971). Current data indicate that these per- centages are approximately the same today, but the total load is substantially reduced.

Temperature Water temperature in the upper Colorado Basin varies widely. The greatest difference occurs during the summer months when water in the high mountain streams remains near freezing while waters of the main stem may reach 32°C (90°F). Changing water temperatures in the upper basin occur naturally through climatic changes in elevation and region; the river generally warms as it flows downstream. Dramatic changes in water temperature are generally associated with point sources such as municipal and industrial wastes, and irrigation return flows. These sources may result in elevated temperatures in the receiving waters, but the added heat is usually dissipated in a relatively short distance from the source by radiation, conduction, and evaporation. Temperature modification also occurs when a river is impounded. The resulting reservoir thermally stratifies and the cold waters of the lower depths can create significant biological changes if released downstream. The greatest modifications of this type are found below main stem reservoirs, particularly those at high elevations. Flaming Gorge Dam, for example, impounds the cool waters of the upper Green River on the Utah- Wyoming border. Thermal stratification occurs in the reservoir proper, and withdrawals from the deep levels of the reservoir in significant temperature changes in the river below the dam. The general effect of Flaming Gorge Dam is an increase in outflow temperature during the winter and a decrease during the summer (Pearson 1967; Utah Division of Wildlife Resources 1977). Mean monthly preimpound- ° ° ment temperature ranged from 0.0°C (32°F) to 19.5 C (67 F) at Greendale, about 0.8 km (0.5 mi) below the dam. Post-impoundment monthly means ° ° ranged from 4.0°C (39°F) to 9.5 C (49 F) (U.S. Department of Interior 1977). Minimum water temperatures before impoundment occurred in the period December to February and maximum temperatures occurred in July. After impoundment, minima and maxima occur in March and in November, respectively (Pearson 1967).

32 Temperature and flow levels are often very erratic downstream from dams. Low water temperatures in the summer usually occur at high discharges. Flow regime is often unpredictable because of dramatic fluctuations in diurnal discharge. A good example of these changes occurs below Flaming Gorge Dam. The primary purpose of this structure is to regulate and store flood waters of the Green River and to generate hydroelectric power. Discharge is thus controlled largely according to peak energy demands. The Bureau of Reclamation proposes to modify the Flaming Gorge Dam penstocks to make the temperature of the river below the dam more nearly resemble preimpoundment values. Presently, the penstocks withdraw water from the cold hypolimnetic zone of the reservoir. The proposed modifications would enable withdrawal of water from the warmer epilimnetic zone. Similar changes have also occurred below Navajo Dam on the San Juan River and below Glen Canyon Dam on the mainstem Colorado River.

2_11_ The waters of the upper Colorado basin generally range in pH between seven and eight. Frost et al. (1964) and Woodburry (1960) found that pH in the Colorado River is a relatively stable parameter that exhibits little natural variation except where foreign materials are introduced. Point source effluents, such as those from acid mine drainage, often cause large changes in pH and preclude the survival of aquatic life. Effects of such drastic changes are observed near numerous mineral recovery operations in the upper basin (U.S. Department of Interior 1977; Morgan and Wentz 1974; Wentz 1975). The first apparent effect of lesser changes in pH is often observed in the macroinvertebrates, particularly the may- flies (Gaufin 1973). Those invertebrates exposed for prolonged periods under these changes may survive but molting, growth, and reproduction may be decidely affected. Point source acids tend to dissipate downstream. The distance required depends primarily on the buffering capacity of the water and the dilution ratio of the stream flow to the acid discharge. Most acid point sources are neutralized rather rapidly.

33 Alkaline discharges may also present a problem to the aquatic biota. Alkaline mineral extraction such as trona (sodium sesquicarbonate) is common in the Green River basin. Should a spill occur from an evaporat- ing pond, pH values as high as 10.5 could occur in the Green River. No existing aquatic organisms in the river could be expected to survive such a change. At a pH of 10.5, soft tissues of aquatic organisms are dissolved; even the resistant chitinous exoskeleton of aquatic insects is softened and gradually dissolved. Oily compounds are rapidly changed to soluble soaps and washed away. A classic example of this effect is the loss of feather oils necessary for flotation of waterfowl and their subsequent drowning when they land on trona evaporation ponds. Unlike acid discharges which are rapidly neutralized by naturally occurring carbonates, alkaline carbonate discharges must be neutralized under natural conditions by carbonic acid which is formed when carbon dioxide diffuses into the water from the air. This process is slow compared to the active solution of carbonates by acid; and alkaline pH changes are neutralized much more slowly than acid pH changes.

Dissolved Oxygen Minimum levels of dissolved oxygen (DO) are essential to aquatic life. Waters of the Upper Colorado Basin generally maintain DO levels well above these minima (Frost et al. 1964; Woodbury 1960), but marked reductions in DO are often found below some municipal and industrial discharges (U.S. Department of Interior 1977). The high organic matter in these discharges often creates high biochemical oxygen demands (BOD). This problem is expected to decrease with improved regulations and the 1983 "zero discharge" requirement. Some streams may also have wide diel variations in DO because of extensive algal production. During daylight hours, algae produce oxygen by photosynthesis. Oxygen concentrations rapidly pass the saturation point and the excess oxygen is lost to the atmosphere by diffusion. Dur- ing darkness, the algae require oxygen for respiration, and may reduce oxygen saturations to less than 30 percent. This effect generally occurs in the high mountain streams or the small clear rivers of the upper and

34 intermediate zones (Kadlec and Fowler 1977). Unless the algal growth is the result of unnatural nutrient enrichment, this condition rarely lowers oxygen saturations sufficiently to cause damage to the aquatic life. Reduced levels of dissolved oxygen often occur in deep man-made impoundments of the Colorado River. Water in a reservoir tends to stratify according to temperature and thus, density. The water near the bottom is depleted of oxygen by chemical and biological processes. Since this water is rarely exposed to the atmosphere and diffusion of oxygen across the temperature stratification is very slow, the bottom waters remain devoid of oxygen. Anaerobic conditions are known to exist in the lower depths of some reservoirs, especially Flaming Gorge. As releases of anaerobic waters are made through the power plant, the water is quickly oxygenated by the turbulent mixing of the water with air.

Other Water Quality Parameters

:S Water quality parameters in addition to those already discussed, and which are considered in this evaluation include: carbonates, calcium, chloride, conductivity, magnesium, phosphate, potassium, silica, sodium, sulfate, and turbidity. Except for isolated studies of these ions (such as their effect on crops), their significance in the waters of the upper basin is not summarized in the literature. Specific measurements of these ions are available in records of the U. S. Geological Survey. These data are the result of monthly, bimonthly, or trimonthly samples form numerous stations. The records are too voluminous to summarize as they are presented. The following is, therefore, a brief overview of the status of these ions in the waters of the upper basin.

Carbonates. Most of the carbonates (carbonate, CO3, and bicarbonate,

HCO3 ) which occur in natural waters have their source as carbon dioxide from the atmosphere. Carbon dioxide combines with water to form carbonic + acid, H2CO3, which dissociates to hydrogen ions, H , and bicarbonate ions, - r- HCO In the presence of hydrogen acceptor ionic species, a further 3 + dissociation of bicarbonate to additional hydrogen ions, H , and carbonate

rs ions, CO3, may occur.

35 The equilibria between carbon dioxide and the carbonates is complex and pH dependent. These equilibria also provide nearly all of the buffering capacity of natural waters. At the pH values which are typical of the upper Colorado River basin, the bicarbonate ion constitutes about 81 to 96.5 percent of the carbonate species present. The carbonate ion constitutes less than one percent of the carbonate species present at pH eight, and is essentially absent at lower pH values. Carbonic acid ranges from about 19 to 2.5 percent at pH seven and pH eight, respectively. The quantity of bicarbonates in solution is dependent on the types and amount of cations (e.g., calcium, magnesium, etc.) which are in solution and can provide electro-chemical balance for the carbonate species. At low levels of salinity, the concentrations of all ionic species are low, but because carbon dioxide from the air and decaying vegetation is usually more plentiful than other anionic species such as chloride or sulfate, carbonates (as bicarbonate) may be the predominant anion. At higher salinities, carbonates increase, but other anions may increase faster because of leaching of shales and other marine rocks. Thus, in the intermediate and lower zones, sulfate and chloride may be more abundant than carbonates in the waters of the upper Colorado River basin. At high levels of algal productivity, carbon dioxide uptake by the algae shifts the equilibrium towards carbonate. This shift is accompanied by an increase in pH. If calcium is present and the concentration of carbonate exceeds the solubility of calcium carbonate, calcium carbonate will precipitate as marl. This phenomenon is frequently observed in clear waters of the intermediate zone when algal production is enhanced by nutrient enrichment from municipal sewage discharges. More extensive discussions of carbonate, bicarbonate, carbon dioxide and alkalinity phenomena may be found in Hem (1970) and Garrels and Christ (1974). Calcium. In most natural fresh water, calcium is the most abundant or second most abundant cation. Calcium is very widely distributed, and is found in both igneous and sedimentary rocks. Calcium is low salinity ++ solutions exists primarily as the divalent cation, Ca . As salinities increase, calcium, like other divalent cations may form undissociated ion pairs. The two which are probably most important in the Colorado

36 + Basin are CaHCO3 and CaSO4. Because the solubility of calcium carbonate, CaCO is very low, pH changes which shift the carbonate equilibria signi- 3' ficantly towards carbonate may cause the precipitation of calcium as cal- + cium carbonate. When calcium is bound in the ion pair CaHCO it is not 3 ' affected by shifts in carbonate equilibria so long as it remains bound. This allows higher concentrations of calcium to remain in salution than ++ would be possible if only the divalent Ca were in solution. Similarly, the CaS0 ion pair, which can exist undissociated allows higher dissolved 4 calcium levels to exist than would be possible with only divalent calcium ions. In the Colorado drainage, headwater and intermediate zone streams are usually predominantly bicarbonate anion streams. Calcium is the predominant cation in these areas. Progressing downstream from the headwaters, concentrations of dissolved ions increase. The rate of increase is slower for calcium than for other cations, especially sodium, so that by the lower zones, calcium is no longer the dominant cation. Chloride. Chloride ion is present in almost all surface waters, but concentrations are usually low in inland waters. Since the chloride ion is not affected by most of the processes which alter the other ion concentrations, chloride, once in solution, tends to remain in solution. Major chloride sources are precipitation and sedimentary rocks of marine origin. Some mineral springs introduce additional chloride as well. In the Colorado Basin, chloride concentrations in the headwaters are very low. Evapotranspiration losses of water result in increasing chloride concentrations downstream. Irrigation return flows which have leached soils derived largely from marine deposits such as are common in the intermediate and lower zones contribute significantly to chloride concentrations in the Colorado Basin streams. Conductivity. Electrical conductance or specific conductance is a measure of the amount of electric current that will pass through a water sample under specified conditions. Conduction of an electric current depends upon the actual movement of ions through the water sample. For dilute solutions, the more ions that are present the greater the current that will pass through the water. At higher ionic concentrations, ionic

37 interferences prevent a linear increase in conductance with increasing ionic concentration. Conductance also varies with the ionic species present. Ions such as sulfate and chloride are more mobile in water and conduct current more easily than less mobile ions such as c„?lcium and magnesium. Thus, in a given body of water, conductance and ionic concentrations (salinity or total dissolved solids) may be related at dilute concentrations but the relationship may not hold at higher concentrations. The relationship of conductance and ionic concentration in different bodies of water may (but usually does not) remain the same because of varying ionic concentration. In the upper Colorado basin, conductances of less than 100 micromhos (umho) are found in headwater streams of low ionic content. Conductances increase downstream and may reach values of several thousand umho in the lower zones. Magnesium. Magnesium, like calcium, is a divalent cation and is one of the major components of hardness in natural water. The chemical behavior of magnesium in solution is quite different from that of calcium. Magnesium carbonates are relatively soluble and exist in more structural and combinatory forms than do calcium carbonates. Magnesium is also not so prevalent in rock and soil as is calcium. Thus, magnesium is usually not present in water at concentrations as high as those of calcium, but the ration of magnesium may be increased by differential precipitation of calcium. In the upper Colorado basin, magnesium is usually present at much lower concentrations than calcium. Magnesium concentrations are also usually lower than sodium concentrations except in headwater streams draining dolomitic [CaMg(CO3)2] regions. Very high magnesium concentrations are usually found only in mineral springs. Magnesium levels in the upper Colorado Basin are most frequently less than 100 mg/l. In headwater areas, magnesium concentrations are seldom over 50 mg/1 gith values of 10-30 mg/1 most common. Phosphate. Phosphorus is a major plant nutrient. It occurs in several chemical forms in surface waters. The most easily utilized form for algae or macrophytes is the ortho-phosphate form. This form is

38 usually present in only low concentrations (<0.05 mg/1 as phosphorus) in unpolluted waters. In polluted water where pollution is from domestic sewage or irrigation return flows, ortho-phosphate levels frequently exceed 1.0 mg/1 as phosphorus. Organically bound phosphorus is much more common in surface water than ortho-phosphate, but it is far less available to macrophytes and algae. Although phosphorus is often considered to be a limiting nutrient for algae and macrophyte growth, phosphorus in the upper Colorado basin is present in almost all analyses at amounts known to be above limiting levels and should not be considered limiting to aquatic production in the basin. Other factors such as temperature, light, and turbidity are most likely limiting in the upper basin. Potassium. Potassium is an essential plant nutrient and is abundant in the earth's crust. However, potassium is seldom found in concentrations approaching those of sodium (which exhibits similar chemical behavior in many laboratory reactions). At least two reasons are postulated for the differences in surface water concentration of these two elements: potassium bearing rocks are much more resistant to solution than sodium bearing rocks, and sodium, once in solution, tends to remain in solution while potassium is rapidly reincorporated into the structural matrix of the rock weathering products. A number of other chemical pathways may also control potassium concentrations in surface waters, but the research to verify and elucidate potassim reactions in surface waters has been largely neglected. Potassium levels in the upper Colorado basin exhibit a relatively narrow range of concentrations which are much more independent of flow than are other ionic concentrations. Ranges in most waters are usually between two and 15 mg/l. Silica. Silicon is the second most abundant element in the earth's crust, and is present in large quantities in virtually all rocks and soils. Silicon occurs in numerous chemcial-structural configurations, none of which is readily soluble in water. Solubilities increase markedly with increasing temperature, but even at high natural tempera-. tures, solubilities are low compared to most other elements found in water. The most likely form of silicon in solution is believed to be

39 silicic acid (H SiO ) in an unionized form. Concentrations of silicon 4 4 in the upper Colorado basin are similar to those observed in other surface waters and range from one to 30 mg/l. Sodium. Sodium is abundant in rocks and soils in all areas, and is easily brought into solution by natural weathering processes. Once sodium is in solution, it tends to stay in solution since no common precipitation reactions exist for sodium in nature. Except in very concentrated solutions, sodium is present in water as the ion Na . Because sodium tends to stay in solution while other dissolved elements are subject to a variety of precipitation reactions, sodium concentrations increase both with evaporation and leaching in a downstream progression. Irrigation return flows may often be high in sodium for this reason. In the upper Colorado Basin, sodium levels generally begin to exceed calcium levels in the intermediate zone. Usually levels at this point will be around 100 mg/l. By the time water reaches the lower zone, sodium levels frequently range upward of several hundred milligrams per liter. Values vary widely with variations in flow and even in the lower zone, sodium values may be much less than 100 mg/1 during high flow periods in the spring. Sulfate. Sulfate is found extensively in sedimentary deposits such as are common in the lower and intermediate zones of the upper Colorado basin. Sulfate may occur as gypsum in the pore spaces of sedimentary rocks. In the upper Colorado basin the latter form is common. Gypsum is relatively soluble in water, and solubility is increased with higher levels of salinity. Equilibrium levels of sulfate in water in contact with gypsum range from about 1500 to over 1800 mg/l. Because of other ionic combination forms, such as dissolved but undissociated calcium sulfate, analytically determined sulfate levels of several thousand milligrams per liter are common. The presence of undissociated calcium sulfate, which does not contribute to electrical conductance but does contribute to total dissolved solids, is one of the principal reasons that conductance provides a poor measure of total dissolved solids. Turbidity. Turbidity is an arbitrarily defined measure of the quantity of light-scattering materials present in water. Light- scattering materials may be abiotic, such as silt or sand particles, or they may be biotic, such as phytoplankton and zooplankton. Turbidity, as measured by light scattering methods may bear a close relationship to the gravimetric determination of suspended materials if the particulate sizes are relatively small and of uniform size. If a large variation in particle size exists or if predominantly large particles (e.g., larger than 0.1mm) are present, turbidity and suspended particulate material may show little correlation. Organic sources of turbidity, both living and dead, are unstable and may coagulate or break up; both circumstances result in steadily lowering turbidities in the period immediately after sample collection. Thus, turbidities with an appreciable organic component usually bear little relationship to quantity of suspended materials. In the lower and intermediate zones of the upper Colorado basin, most turbidity is the result of inorganic sediment in suspension. Frequently, a wide size range of particles results, and thus, turbidity is a poor indicator of quantities of suspended materials. In the upper zones, much of the turbidity during low flows is the result of organic materials, and turbidity in this zone is also a poor indicator of suspended materials. Probably the greatest utility of turbidity measurements in the upper Colorado basin is as a measure of light penetration which may be limiting to the growth of periphytiC algae.

41 II. BIOLOGICAL COMPONENTS

Introduction A working knowledge of the biological components of the upper Colorado River ecosystem is essential (as are the abiotic components) to a full appreciation of the status and habitat requirements of important Colorado River fishes. This section discusses the primary producers, invertebrates, and fishes, and attempts to bring together what is known about the upper Colorado River. More often than not, data concerning a particular group are limited and therefore only a general picture will be developed. The focus of our discussion is primarily upon the trophic dynamics of this system, for each aquatic bio-component plays an important role. Non-aquatic entities, such as avain predators have a minor impact and therefore are not discussed. To reiterate, this report deals with the upper Colorado River (Lake Powell and above) and is divided into three zones: upper, intermediate, and lower zone. For further clarification of the zones, refer to the introduction of this report.

Primary Producers Primary production in lotic environments is frequently low, and varies with water clarity, nutrient level, and substrate (Hynes 1970, Odum 1971). This generalization certainly applies to the upper Colorado River system, primary production is greatest in the upper and intermediate zones and is almost non-existent in the lower zone. The controlling factors appear to be water clarity and substrate scouring. Large quantities of algae can be found in the upper Yampa River. Water clarity in this area is good, and except during spring runoff, suspended solids are low, hence little scouring and greater primary Productivity. Flowers (1963) described the algal flora of the Green and Yampa Rivers of Dinosaur National Monument (intermediate zone) as poor, due to scouring and reduced light penetration. Winget and Baumann (1977) attributed the reduced algal growth in the Colorado River in Westwater Canyon to poor light penetration and low phosphate levels.

42 Westwater Canyon is in the overlap areas between the intermediate and lower zones. Frost et al. (1965) found the primary productivity to be low in the Colorado River near Moab, Utah (lower zone), and attributed it to scouring activity of the high level of suspended solids. The Colorado River system, except in the upper zone, has less potential for in-situ primary production than most other riverine systems because of the high level of suspended solids, reduced light penetration erratic changes in flow and scouring effects. Most streams receive their primary energy input from allochthonous sources (Hynes 1970). Many aquatic organisms in the Colorado River in the intermediate and lower zones of the upper basin depend primarily on detritus as a food source, since in-situ production is so low (Frost et al. 1964); anyone who has been in the area during heavy rains can attest to the magnitude of allochthonous materials entering the river system. No quantitative estimate of this material has been attempted, but certainly the amount is extremely large and varies seasonally. Detailed studies on the use of allochthonous material by the resident fauna have not been made. It appears from the observation of several investigators that much of the woody material provides an important habitat for various aquatic invertebrates. Seeds, leaves, and other softer materials are eaten by omnivorous fishes (Vanicek 1967; Taba, Murphy, and Frost 1965) and certainly comprise a food source for invertebrate detritivors. It is very doubtful that plant material represents a limiting factor in the upper basin ecosystem. The riparian vegetation in the upper basin has undergone a major change in species composition and quantity during the last century. Willow (Salix sp.) was the dominant vegetation type along river banks with occasional large stands of cottonwood (Populus sp.) in level areas. The willow has been replaced in many areas by the introduced Salt Cedar (Tamatix penandra). The effects of this change on the river's allochthonous organic budget is not known, but Frost el al. (1965) considers detritus from riparian vegetation a significant contribution to the primary energy source in the river.

43 A major exception to the above generalization occurs in parts of the intermediate and upper zones, and for some distance below large dams. In these areas large quantities of filamentous algae are common, for the clear, nutrient-rich water is ideal for rapid growth. A portion of the algae is washed far from its point of growth and adds to the energy source of downstream communities. The amount of allochtonous materials is reduced in river systems below dams but no quantification has been made. The major energy source for this system lies with the primary producers and allocthonous material. Primary productivity decreases as we move from the upper zone to the lower zone and the importance of allocthonous material increases. These primary energy sources are the key to overall ecosystem productivity and any major alteration will certainly effect a change in the consumer populations of invertebrates, fish, etc.

Invertebrates Benthic macroinvertebrate composition generally adheres to a similar pattern within each of the three zones. The upper zone is dominated by Ephemeroptera, Plecoptera, Tricoptera, and Diptera (Sublett 1976, Smith 1976). The intermediate zones retains these four orders, but a gradual shift in species and families occurs. Burrowing forms and species adapted to turbid conditions appear (Winget and Bauman 1977) and filter feeders are less common (Ames 1976). In small streams, Hemiptera, Odonata, Coleoptera, and Diptera often dominate warm, slower flowing sections (Sublette 1976, Smith 1976). In the lower zone, burrowing insects and species adapted to turbid conditions predominate (Winget and Bauman 1977, Pearson 1967). Additional forms adapted to slower water also appear in sheltered areas in the lower zone. Major factors responsible for these changes in composition and abundance appear to be substrate characteristics and suspended sediment load (Ames 1976, Winget and Bauman 1977). A very important, although rather small source of secondary production Involves aquatic crustaceans, often forms considered planktonic. Such

44 A major exception to the above generalization occurs in parts of the intermediate and upper zones, and for some distance below large dams. In these areas large quantities of filamentous algae are common, for the clear, nutrient-rich water is ideal for rapid growth. A portion of the algae is washed far from its point of growth and adds to the energy ource of downstream communities. The amount of allochtonous material is reduced in river systems below dams but no quantification has been m e. The maj r energy source for this system lies with the primary producers and llocthonous material. Primary productivity decreases as we move from th upper zone to the lower zone and the importance of allocthonous mate ial increases. These primary energy sources are the key to overall eco stem productivity and any major alteration will certainly effect a c ange in the consumer populations of invertebrates, fish, etc.

Invertebrates Benthic macroinvertebr te composition generally adheres to a similar pattern within each of the th ee zones. The upper zone is dominated by Ephemeroptera, Plecoptera, Tric ptera, and Diptera (Sublett 1976, Smith 1976). The intermediate zones re ains these four orders, but a gradual shift in species and families occu . Burrowing forms and species adapted to turbid conditions appear inget and Bauman 1977) and filter feeders are less common (Ames 1976). small streams, Hemiptera, Odonata, Coleoptera, and Diptera often d mate warm, slower flowing sections (Sublette 1976, Smith 1976). In lower zone, burrowing insects and species adapted to turbid conditi ns predominate (Winget and Bauman 1977, Pearson 1967). Additional forms a apted to slower water also appear in sheltered areas in the lower zone. Major factors responsible for these changes in composition and abundance ppear to be substrate characteristics and suspended sediment load (Ames 197 Winget and Bauman 1977). A very important, although rather small source of secò4Iary production - Involves aquatic crustaceans, often forms considered plankton'. Such

44 organisms as copepods, cladocerans, ostracods, etc. are abundant almost anywhere in shallow, protected areas with warm water and an organic silt substrate. These organisms are important components in diets of larval and juvenile fish (Vanicek 1967). No studies have been identified concerning this group of organisms in the basin, but because of their cosmopolitan nature, they can be assumed to exist wherever suitable habitat exists. In many ways, this group may be the most important fraction of the aquatic invertebrates in the lower zone. Young fish probably rely on this source rather than allochthonous material for most of their food. Larger fish rely more on allochthonous materials because benthic macroinvertebrates are either very scarce or difficult to locate in the turbid water (Vanicek 1967; Taba, Murphy, and Frost 1965). Terrestrial insects represent a significant item in the diets of many species of fish. Large numbers of such insects are washed, blown, or otherwise deposited into the river. The importance of this allochthonous secondary production is seen in the preponderance of such species in fish stomachs at certain times of the year (Vanicek 1967; Taba, Murphy, and Frost 1965) although there has been no attempt to quantify this phenomenon. The intensive surface feeding that many fish species exhibit immediately after rainstorms is another indication of the importance of this food source. An introduced crayfish, Orconectes virilis, was found to be rather common in the Colorado River below Moab, Utah, by Taba, Murphy, and Frost (1965). It was preyed on quite 'heavily by channel catfish. Smith (1976) reported a crayfish from the Mancos River, but did not identify it to species. Crayfish are also reported from the Gunnison and Colorado Rivers near Grand Junction, Colorado (William Miller, personal communication). Other aquatic invertebrates, especially snails and small clams, have been reported in the upper Colorado system. Their importance in the trophic structure of the ecosystem is probably small.

Fishes Fishes of the upper Colorado River are generally distributed in accordance with the three ecological zones described earlier. Each zone has typical species that are somewhat restricted to it, and other species

45 that either overlap into the zone from an adjacent area or are ubiquitous and found in several zones. Typical native species for the upper zone are Colorado Cutthroat trout (Salmo clarki pleuriticus), speckled dace (Rhinichthys osculus), mottled sculpin (Cottus bairdi), and mountain whitefish (Prosopium williamsoni) (the latter is native to the Green River tributaries only). The roundtail chub (Gila robusta robusta) and bluehead scuker (catostomus discobolus) are typical species of the intermediate zone. The lower zone includes large river fishes such as the bonytail chub (Gila elegans), razorback sucker (Xyrauchen texanus) and, in a more restricted degree, the humpback chub (Gila cypha). Several species are found in all three zones. The speckled dace and the bluehead sucker are found in conjunction with trout in the upper zone as well as in the main channels in the lower end of the upper zone, and are distributed throughout the other zones downstream. The Colorado squawfish (Ptychocheilus lucius) is found in both the intermediate and lower zones, but reaches its greatest abundance and success in the latter. The intermediate zone may represent critical habitat for them. Several species of exotic fishes have been transplanted into the upper basin, many inadvertently. No introduced species have become abundant in all three zones. Several are very abundant in the lower and intermediate zones, notably the channel catfish and red shiner. Other species, such as green sunfish (Lepomis cyanellus), fathead minnow (Pimephales promelas), and carp (Cyprinus carpio) are found throughout the lower and intermediate zones, but are abundant only in widely separated habitats that suit their needs. The introduced trout species in the upper zone are a special case in that they are often maintained by annual stocking. The following section looks closely at the fishes of the upper Colorado River Basin. While the primary focus of the report lies with the threatened and endangered fish, the species accounts describe the general status, placement, and prominence of many resident fishes. III. SPECIES DESCRIPTIONS

Introduction This section discusses in greater detail the rare and endangered fishes as well as other important fishes of the upper Colorado River system. A discussion of speciation is presented in order to summarize the magnitude of the problem concerning the "Gila Complex." Because these fish are extremely important, it is necessary to know, whenever possible, with what taxon we are dealing. On the other hand, when uncertain, it is important to appreciate the reasons for the uncertainty. Are we talking then about an endangered species or subspecies? Although this distinction is sometimes difficult to ascertain conclusively and is open to debate, it is important to try, and, as a minimum, present the foundation and rationale for our discussion. The question of taxon is not essential when considering the Endangered Species Act, for the definition is not limited by descriptors such as "species" or "subspecies." The following discussion is presented to clarify species-subspecies divisions, intergradation, hybridization, and gene flow concepts. A species, in a modern concept, is a genetically distinctive group of natural populations that share a common gene pool and are reproductively isolated from all other such groups. Another way of saying this is that a species is the largest unit of a population within which effective gene flow (exchange of genetic material) occurs or can occur under natural conditions. This concept of species says nothing about morphological or other historical taxonomic variation, although most species are readily separated morphologically, physiologically, ecologically, or behaviorally. Effectively, this genetic species concept says that, if there is complete intrinsic reproductive isolation between two sympatric outwardly identical populations (i.e., if there is no gene flow), then these Populations are two different species. In contrast, if two populations appear to be significantly different but have effective gene flow between them, then those populations belong to the same species. Modern species concepts characterize a species as follows:

47 1) Individuals of a species possess common distinctive characteristics. 2) Potential gene flow exists throughout the species. 3) Members of congeneric species (species in the same genus) do not usually hybridize; or, it they do, reproductive isolation is reinforced by sterility barriers or negative selection against hybrids. 4) Intermediate or transitional forms are usually not found between two closely related species. 5) Congeneric species generally have distinct ecological (niche) differences, but there may be some overlap. A situation involving two questionable fish species brings to focus the many problems and practical difficulties concerning systematics. For instance, using our gene flow definition of a species, how do we ascertain if two allopatric (geographically isolated ) groups of fish are two separate species or subspecies of one species? One method would be to attempt artificial hybridization, which certainly would result in one-sided evidence. If the two groups do not hybridize, evidence weights heavily toward a two species determination without knowing the effect of laboratory captivity; if they do, we call them subspecies without knowing if the conditions in the natural situation would allow for their complex reproduction requirements. If they could not reproduce naturally for whatever reason, they would be reproductively isolated, no gene flow could occur and therefore they would be considered two species. This problem, coupled with the fact that many animals will not breed in captivity anyway, demonstrates that the experimental approach is not easily justified unless hybrids produced are sterile or fail to develop. Accordingly, systematists attempt to answer the question by asking another: Are the morphological or other differences between the two populations great enough so that they probably would not interbreed if they did come together naturally? The problem in answering this question is obviously differences in judgment. This problem is brought out only to impart an appreciation of the complexity involved in ascertaining speciation conclusively.

48 A subspecies is a genetically distinctive geographic subunit of a species. The key term in this case is "geographic." Ordinarily, individuals of different subspecies of a species are completely interfertile. They hybridize readily whenever they come together. If subspecies territories come into contact, intergrades or transition forms are frequently found. In contrast, when two species territories overlap, no intergrades are produced. The principal factor that keeps a subspecies separate then is geography. Different subspecies inhabit different regions, and hence, the genetic pool maintains its supspecies integrity. Generally, the difference between two subspecies is slight. The visible, readily identifiable characteristics may be so small, or the morphological range so broad (scale numbers), that only an expert can tell the difference; and frequently even an expert must have many specimens for comparison in order to run a statistical analysis on the characteristics. It is also important to understand how species originate, for this process is a critical part of the problem in dealing with the "Gila Complex." Let's assume that we have a single species of fish--species A-- which has 80 lateral line scales, During the last glaciation these fish were forced south, and some remained there when the glacier retreated. Being in a warmer climate with different foods and growing a bit larger, they differentiated and typically had 100 scales. This group would be recognized as subspecies Al of species A. They are not allopatric and different from the original population and thus represent a subspecies. Given enough time, each population will continue to differentiate (evolve) to a point where reproductive isolation is maintained even when brought together again. We now have two separate species, A and B (formerly Al). The gradual nature of this differentiation/speciation presents complex problems. Let's look at only two of these. As the glacier retreats, it may leave other remnant populations in equally isolated areas so that one would find intergrades (primary intergrades) (say, 90 scales) which could also be called a subspecies. On the other hand, two subspecies might come together (before genetic reproductive isolation had occurred) and hybridize, producing secondary

49 intergrades. Both of these types of intergradation require differentiation (speciation) in isolation (allopatric differentiation) but not sufficient isolation and differentiation for reproductive isolation when in contact. Let's summarize the problems thus far and then move into the humpback/ bonytail problem. Using the modern concept based on gene flow as a foundation for our species concept, then we would have to say that many species today are really subspecies of a single species. The cutthroat and rainbow trout are considered separate species, and in their native range on the Pacific Coast both have historically coexisted without hybridizing. When non-native rainbow trout are introduced to natural cutthroat trout populations they often hybridize. Since they hybridize, are they then a subspecies of one species? Another example is the genus Notropis, with over 100 recognized minnow species; hybridization between many of these species occurs in certain parts of their range. Does this mean that they are all subspecies of a species? Certainly most systematists would answer no. It is obvious the term "humpback chub complex" needs to be better delineated. Is each member of a "complex" an endangered species? Are the intermediate specimens the result of hybridization between elegans and cypha? If so, are the hybrids fertile? Are there areas where unhybridized populations of cypha and elegans still exist? The history of nomenclature (both common and scientific names) of the chubs of the genus Gila of the Colorado River basin is confusing. This is due to their morphological variability within each species and to the apparent breakdown of reproductive isolation resulting in hybrid intermediate specimens. Jordan (1891) recognized two distinct species in the upper basin, the bonytail chub, Gila elegans, in the mainstream environment and the roundtail chub Gila robusta, typically found in tributaries. Later authors combined the bonytail and roundtail chubs into a single species, G. robusta, usually with subspecific recognition for each; but it was a common practice to use the common names interchangeably. Another subspecies, G. robusta seminuda, was sometimes recognized for a partially scaled form. Miller (1946) described the humpback chub, Gila cypha, and discussed the three "subspecies" of G. robusta.

50 Holden and Stalnaker (1970) presented data to conclusively demonstrate that G. robusta and G. elegans are separate species and that the name G. Tobusta seminuda more correctly should be restricted to the roundtail chub of the Virgin River drainage. However, because of numerous intermediate specimens (Holden and Stalnaker, 1970 - Figure 4), they used the term "humpback chub complex" and considered cypha only as a subspecies of G. elegans. To better delineate the "humpback chub complex" and decide if the bonytail chub and the humpback chub should be recognized as two separate species or as two subspecies of a single species, it is appropriate to interprete the situation in the light of modern systematic concepts. The biological species concept stresses reproductive isolation; thus Mayr (1969) defines a species as ". . . groups of actual or potential interbreeding natural populations that are reproductively isolated from other such groups." It is common among freshwater fishes that species classified in the same genus lack sterility barriers to insure reproductive isolation, and such isolation is maintained by differences in time and place of spawning or behavioral differences when they occur together. Such reproductive isolation is reinforced by niche separation of the species to the extent that each species is best adapted for a particular niche and any hybrids produced would be at a disadvantage to either of the parent species. In the case of species versus subspecies recognition of two distinct forms, the factor of intergrades is considered. For example, if a species was separated into a northern group and a southern group during the last glacial period and these two groups are recognizeably different, it is likely that early taxonomists named them as two different species. Later, more comprehensive studies may reveal that their ranges overlap and an intergradation occurs in the contact zone from hybridization. From this it can be assumed that the two have not attained the degree of genetic divergence to maintain reproductive isolation when they occur together and should be treated as two subspecies of a single species. It would appear obvious that the roundtail, bonytail, and humpback chubs have been sympatric in the Colorado River basin for eons. To

51 attain the degree of morphological differentiation observable in the typical forms of these three chubs, they must have maintained a high degree of reproductive isolation under the original environmental conditions of the Colorado River basin. Niche separation is implied from the preferred habitat originally occupied by the three chubs and from the very different response each has made to the changing environment. This "sorting out" effect induced by a modified environment has virtually eliminated bonytail and humpback chubs while the roundtail chub remains relatively abundant and widely distributed. If it is accepted that the changing environment stimulated a breakdown of reproductive isolation resulting in hybridization and intermediate specimens of the "Humpback chub complex," then the proper taxonomic arrangement of the genus Gila in the upper basin should recognize the roundtail, bonytail, and humpback chubs as three separate species. This report considers G. elegans and G. cypha as valid species. The need now is to study the current extent of hybridization and to find pure populations, if they yet exist, before their status can be determined conclusively. Gila hybrids are not known to be fertile; if they indeed are not, this factor would agree with the gene flow concept and support the conclusion that they are indeed two species. This section discusses in detail the threatened and endangered fish and other important fishes of the upper Colorado River system. All available literature and information on the life history and distribution of each species was compiled and reviewed for these descriptions and little or no additional data exists. A gap in the discussions indicates a lack of data concerning the topic. Each of the species descriptions is organized according to the following outline:

SPECIES DESCRIPTIONS

A. Present and Past Distribution

1. Past 2. Present a. by basin b. within each basin

52 B. Present and Past Abundance

1. Past 2. Present

C. Habitat Requirements

1. General Requirements 2. Spawning Requirements 3. Nursery Requirements

D. Foods

1. Adult 2. Juvenile 3. Fry and Larvae

E. Age and Growth

F. Movements

G. Predators

H. Diseases and Parasites

I. Hybridization

J. Taxonomic Problems

K. Gaps in Knowledge

53 COLORADO SQUAWFISH (Ptychocheilus lucius) Girard

The Colorado squawfish is the largest cyprinid native to North America and has been reported to reach lengths up to 6 feet and weights of 80 pounds or more. While there are four recognized species of the genus Ptychocheilus in North America, P. lucius is the only species found in the Colorado basin. Of the other species, P. oregonensis (northern squawfish) is widely distributed in the Columbia River basin, P. grandis (Sacremento squawfish) inhabits the Sacremento River system, and P. umpquae is found in the Umpqua and Siuslaw rivers in Oregon. In contrast with the Colorado squawfish which is considered endangered, the Sacremento and northern squawfishes are abundant to the extent that they are classed as nuisance fish.

Present and Past Distribution Past distribution of the Colorado squawfish included all the larger streams in the basin. It was apparently abundant in most of the streams and was valued as a food fish by the early settlers in the basin. It has been found in the Green River as far upstream as the town of Green River, Wyoming, and may have occurred 30 miles further upstream (Baxter and Simon 1970). In the Yampa River, it has been collected as far upstream as the mouth of Milk Creek just below Craig, Colorado (Holden and Stalnaker 1975a, 1975b). Squawfish have also been collected in the Colorado River as far upstream as Rifle, Colorado (Beckman 1952), in the Gunnison and Umcompahgre rivers to Delta, Colorado (Jordan 1891), in the San Juan River at the Colorado-New Mexico border (Jordan 1891, Olson 1962), in the Dolores River probably below the confluence with the San Miguel River (Lemons 1954, 1955), in the Animas River at Durango, Colorado (Jordan 1891), in the Dueschesne River (Mullan 1975), and in the White River (Everhart and May 1973, Behnke, personal communication). Habitat which may be important for the Colorado squawfish includes the following segments: Green River--from mouth of Yampa to Colorado River.

54 Yampa River--Craig to confluence with Green River. White River--just upstream of Meeker, Colorado, to confluence with Green River. Colorado River--Rifle, Colorado, to Lake Powell. Gunnison River--Delta, Colorado, to confluence with Colorado River. Duchesne River--From Utah to confluence with Green River.

Present and Past Abundance Squawfish were apparently abundant during the early period of settlement in the Colorado River basin, and there are numerous accounts in the popular press about the abundance of this species. No scientif- ically acceptable documentation (quantification) of abundance from early historical times exists, however. Gradual declines in abundance were first noted in the 1930's to 1950's (Kidd 1977; Vanicek 1967). Much sharper declines in squawfish abundance have occurred since the large dams associated with the Colorado River Storage Project were closed in the 1960's (Vanicek 1967, Vanicek, Kramer and Franklin 1970, Holden, 1973, Seethaler, McAda and Wydoski 1976). Vanicek, Kramer, and Franklin (1969) found squawfish common in the Green River between Ouray, Utah, and the mouth of the Yampa River, and most of their collections were juvenil,ps, indicating healthy reproduction. Populations of squawfish in this area have apparently declined greatly since then as only two juveniles have been collected above Jensen, Utah, since 1970 (Holden and Stalnaker 1975a, Seethaler, McAda, and Wydoski 1976). The major factors associated with these precipitous declines appear to be the altered temperature and flow regimes created by large dams and competition with introduced species which are better adapted to the altered temperature regimes. Recent collections by Holden and Stalnaker (1975a, 1975b) document squawfish presence in the Yampa, Green, Colorado, and Gunnison rivers. Parish (1975) notes collection of a squawfish in the San Juan River in New Mexico in 1965; no more recent observations are known from that area. Recent collections in tributaries include the Duchesne (Mullan 1975) and the White rivers (Everhart and May 1973, Behnke personal

55 communication). Previous collections of squawfish in intermediate zone tributaries have all occurred during presumed spawning migrations, but a squawfish collected by Prewitt on April 22, 1977, in the Yampa River at Maybell, Colorado, and during May 1977 near Piceance Creek in the White River indicates that resident populations may also be present in the intermediate zone streams (Behnke personal communication).

Habitat Requirements The Colorado squawfish is generally recognized as a "large river" fish and is usually found in mainstem rivers. The other species of squawfish are found in small tributaries and lacustrine habitat, and this may explain their greater abundances, since large rivers are usually the areas most impacted by large dams. Most adult squawfish are collected from pools, eddies, and backwaters, although they have been taken in riffles and runs. Juveniles also tend to be found in quiet water, usually in backwaters and pools over a silt, sand and rubble bottom. Young-of-the-year are found in small, shallow backwaters, usually with a sand or silt bottom and very warm temperatures (Vanicek 1967, Holden and Stalnaker 1975a, Kidd 1977). Jordan (1891) indicated that the squawfish appeared in collections along with roundtail chubs near the areas where water temperatures became too high for trout. This is the intermediate zone of the Colorado River basin streams.

Most reports from smaller streams are of larger fish; no reports of young-of-the-year or yearling fish are known. Squawfish appear to be found only sporadically in these smaller streams. For example, Everhart and May (1973) reported finding squawfish in the White River, Colorado, but none were found in more recent studies (VTN 1976; Prewitt et al. 1976, Burkhard, personal communication) until Prewitt's 1977 collection. Similarly, squawfish have been found sporadically in the Duchesne River (Mullan 1975, Petengale, personal communication). Because available sampling methods are not highly efficient, these limited data could indicate either sporadic usage of the streams or very low population levels of squawfish. Kidd (1977) has suggested that large (500 by 2,000

56 foot and larger) backwaters are important to squawfish survival near Grand Junction, Colorado. He collected 75 specimens, mainly large fish, from such areas during the three years of a recent study. Collections of young squawfish by Vanicek (1967) in the Green River of Dinosaur National Monument and by Holden (1973) in the Green River below Ouray, Utah, suggest spawning occurs in the river proper, as these young fish were taken in areas where no large or permanent backwaters exist. Observations were made by Toney (1974) of squawfish spawning in the runs at Willow Beach National Fish Hatchery. In the hatchery, spawning occurred over a gravel-cobble bottom with a mean current velocity of approximately 0.02 foot per second, and the eggs were adhesive enough to remain attached to the substrate until dislodged by substrate disturbance. This suggests that spawning could occur in the river in areas of very slow current (about 1 foot per minute), but such current speeds are found primarily in backwater areas. However,' McAda and Seethaler found ripe males and suspected spent females in eddy and backwater areas at the upper end of Lily Park in early August 1975. These fish were captured in areas of considerably more rapid current than 1 foot per minute. Vanicek and Kramer (1969) and Holden (1973) determined spawning to occur after temperatures reached 70F. They based this on ripe and spawned out fish and appearance of young-of-the-year. Seethaler (personal communication) has also found this to be the probable spawning temperature, Toney (1974) reported that captive squawfish spawned in Willow Beach National Fish Hatchery when the water temperature was 72F. Water temperatures had been about 70F for a month when spawning took place on June 30. No data is available concerning substrate type. The squawfish at Willow Beach spawned on a gravel bed (Toney 1974). The area where Vanicek (1967) found young-of-the-year has both gravel and sand bottoms, whereas the area in which Holden (1968) found young was predominantly silt and sand substrate. Toney (1974) noted that squawfish eggs were adhesive but were dislodged by stirring. The eggs were 2.0 mm in diameter and they hatched

57 in four to five days at 72F. Spawning of the Colorado squawfish has never been observed in nature. Early literature contains frequent references to upstream migrations, presumably for spawning. References to spawning in small tributary streams are also numerous, although none are documented with actual observations. (Jordan 1891, Minckley 1973). No collections of young-of-the-year or yearlings are known from small tributary streams.

Foods Young squawfish feed on small crustaceans and chironomid larvae until they reach 50 mm in length. From 50-200 mm length they feed primarily on aquatic insects. At lengths greater than 200 mm they are largely piscivorous (Vanicek 1967). Backwaters at least 20 feet wide and 50 feet long are generally good areas in which to find larger squawfish (Holden personal communication, Kidd 1977). These backwaters are generally full of young fish of several species, indicating that feeding is the probable reason for the presence of the larger squawfish. Don Toney (personal communication) of Willow Beach National Fish Hatchery has noted a seasonal feeding cycle in the adult squawfish he is raising. He said they seldom feed during the winter, but start feeding heavily as spring approaches. After spawning the feeding rate drops.

Age and Growth Little information is available on the age and growth of the Colorado squawfish. Length and weight data have been reported from the Green River by McDonald and Dotson (1960), Bosley (1960), Simon 1946), and

Sigler and Miller (1963). The mean km (weight in grams and total length in millimeters) for data from all these sources was 0.818. Vanicek and Kramer (1969) present additional age and growth data from 182 fish from the Green River below Flaming Gorge Dam.

Movements Several observations of concentrations of upstream-moving squawfish lend support to earlier notes on this phenomenon. R. R. Miller collected

58 a number of squawfish immediately below Flaming Gorge Dam on July 21-24, 1961 (Sigler and Miller 1963). Holden and Stalnaker (1975b) found relatively large numbers of ripe, adult squawfish in the Yampa River in July and August, 1968-1970. Seethaler (personal communication) also observed increased numbers of ripe squawfish in July and August in the Yampa River in 1974-1975. These data suggest a spawning migration for most squawfish populations. McAda and Seethaler (1975) suggest that habitat and forage are the stimulators of such migration, although there are apparently no data to support this hypothesis. The extent of the suspected migration is not known. Kidd (1977) has shown that a self-sustaining squawfish population has been blocked in the Gunnison River for about 50 years. This would suggest that migrations are not necessarily very long in length or that they may not be necessary for survival. Observations by Vanicek (1967) and Holden (1973) would support this as spawning apparently occurred in the same areas where adult populations lived year around. Older fishermen seem to stress the migration of very large individuals. It is possible that the very large individuals did migrate long distances, whereas the smaller fish only move shorter distances.

Predators Historically the Colorado squawfish was the largest fish predator in the Colorado River basin, and it is unlikely that any other predator posed a threat to adult fish. Young squawfish could have served as prey for other piscivorous fishes such as the larger individuals of roundtail chub, but there is no documentation of predation on squawfish. Exotic species probably prey on young and possibly juvenile squawfish, but it is unlikely that any exotic or native fishes prey on the larger adult squawfish.

Diseases and Parasites Vanicek (1967) reported bass tapeworms, Proteocephalus ambloplites, in 65 percent of the Colorado squawfish he collected over 200 mm. He mentioned that Dotson (unpublished data) found tapeworms in 80 percent

59 of the squawfish he sampled. Hagen and Banks (1963) found Lernaea on squawfish they collected from the Green River of Dinosaur National Monument. Seethaler (1977) found rather severe infestations of Lernaea on specimens collected from the Walter Walker Wildlife Area, a large artificial backwater near Grand Junction. Toney (1974) reported that wild squawfish were infected with Myxobolus lernea, Ichthyophthirius, and Saprolegnia parasites upon arrival at the hatchery.

Hybridization Hybridization between the Colorado squawfish and other species has not been reported.

Taxonomic Problems The taxonomy and distribution by basin of the four species of Ptychocheilus are well known. However, taxonomic difficulty often occurs among inexperienced and untrained persons with regard to young which may be confused with the roundtail chub (Gila robusta robusta). Field recognition can be made, however, based on the caudal spot and relatively longer jaw of the squawfish.

Gaps in Knowledge Several important aspects of the life history and habitat requirements of the Colorado squawfish are not known. Actual spawning in nature has never been observed. Thus, preferred spawning habitat parameters such as substrate, current velocity, and water quality are not known. Preferred nursery habitat is also undefined, as is the minimum river size and flow required by the adults for both maintenance and reproduction. No information is available on toxicity of common pollutants or on physical water quality parameters to squawfish life stages.

60 HUMPBACK CHUB (Gila cypha) Miller

Present and Past Distribution The humpback chub was relatively common in preimpoundment surveys of the Flaming Gorge basin in Wyoming and Utah (Bosley 1960, Smith 1969, Sigler personal communication) but is considered extirpated above the mouth of the Yampa River at present. It was also commonly collected in Lake Powell soon after closure of the Glen Canyon dam in 1962 (Holden and Stalnaker 1975a). A single humpback chub specimen was collected from the White River near Bonanza, Utah (Sigler and Miller 1963), and is the only documented specimen collected from other than a large river environment. More recently .this species has been found in the lower Yampa River and Green River of Dinosaur National Monument, Desolation Canyon (Holden and Stalnaker 1975a), and in the Black Rocks and Ruby Canyon areas of the Colorado River near the Utah-Colorado State line and near Palisade, Colorado (Kidd 1977, Holden and Stalnaker 1975a, Behnke personal communication). Collection of a humpback chub was reported from Juniper Springs on the Yampa River during July 1977 (Behnke personal communication). Reproduction is documented only from the Desolation Canyon area of the Green River (Holden and Stalnaker, 1975a). The type specimen was collected at the lower end of the Grand Canyon of Arizona, and original distribution probably included all of the large river habitat in the upper basin. Present distribution appears to be similar to historical distribution except where dams such as Flaming Gorge have modified the habitat. Important habitat for the humpback chub includes the following river segments: Green River--from confluence with Yampa River to confluence with Colorado River. Yampa River--Juniper Springs to confluence with Green River. White River--Colorado state line to confluence with Green River. Colorado River--Palisade, Colorado, to Lake Powell.

61 Present and Past Abundance Little information on present or past abundance is available. The fact that the species was only recognized in the 1940's indicated that it probably was never abundant. The limited and sporadic collection of humpback chubs at present also indicates low abundance.

Habitat Requirements Humpback chub adults are usually collected in or adjacent to swift deep water (Holden and Stalnaker 1975a). This type of habitat is found only in canyon areas of large rivers where channel restriction causes deep cutting to occur. Although the current velocity at the Black Rocks area of Colorado was slow during the fish collections made by Holden in 1976, this area displays swift current during high water periods, and depths of 40-50 feet are common. Juvenile chubs were also collected in this area in a small flowing channel over a rubble-silt bottom (Holden, personal communication). Little is known about the reproduction of humpback chubs. Holden (personal communication) collected a ripe male in the lower Yampa River at the same time that ripe roundtail chub males were collected. This indicated that spawning probably occurs in mid-June to early July at water temperatures of approximately 18C. The occurrence of probable hybrids suggests spatial overlap of spawning areas and tends to support the hypothesis that spawning requirements of Gila cypha and G. robusta robusta are similar. No additional information on the habitat ol spawning requirements of the humpback chub has been identified.

Foods No food habit studies or stomach analyses are known for the humpback chubs. Holden (personal communication) observed humpback chubs feeding on floating materials in a swift run in Desolation Canyon in 1967, and Armantrout (personal communication) observed surface feeding in an eddy at the upper end of Desolation Canyon in 1976. The type specimen was caught by an angler fishing with hook and line, but the lure or bait was • not specified (Miller 1946).

62 Present and Past Abundance Little information on present or past abundance is available. The fact that the species was only recognized in the 1940's indicated that it probably was never abundant. The limited and sporadic collection of umpback chubs at present also indicates low abundance.

Habit Re uirements Hum ack chub adults are usually collected in or adjacent to swift deep water olden and Stalnaker 1975a). This type of habitat is found only in canyo areas of large rivers where channel restriction causes deep cutting to 'ccur. Although the current velocity at the Black Rocks area of Colorado w slow during the fish collections made by Holden in 1976, this area disp s swift current during high water periods, and depths of 40-50 feet ar. common. Juvenile chubs were also collected in this area in a small flowl g channel over a rubble-silt bottom (Holden, personal communication). Little is known about the eproduction of humpback chubs. Holden (personal communication) collecte a ripe male in the lower Yampa River at the same time that ripe roundtai chub males were collected. This indicated that spawning probably occu in mid-June to early July at water temperatures of approximately 18C. The occurrence of probable hybrids suggests spatial overlap of spawni areas and tends to support the hypothesis that spawning requirements of Gila cypha and G. robusta robusta are similar. No additional informatio on the habitat 01 spawning requirements of the humpback chub has been identi ied.

Foods No food habit studies or stomach analyses are known for the humpback chubs. Holden (personal communication) observed humpback ubs feeding on floating materials in a swift run in Desolation Canyon in 967, and Armantrout (personal communication) observed surface feeding in n eddy at the upper end of Desolation Canyon in 1976. The type specimen caught by an angler fishing with hook and line, but the lure or bait not specified (Miller 1946).

62 Age and Growth No data on age and growth of the humpback chub are available in the literature. The type specimen measured 305 mm standard length, and the other specimen referred to by Miller measured 315 mm standard length (Miller 1946).

Movements No information on movements of the humpback chub has been identified.

Predators Predators on humpback chubs are probably limited because of the restricted distribution they exhibit and the fact that few other species in the upper basin find adult humpback chub habitat suitable. Young humpback chubs are more likely to utilize habitat suitable to other species, and predation by any of the other omnivorous-piscivorous species found in the basin is probable.

Disease and Parasites No information is available on diseases or parasites which may infect the humpback chub.

Hybridization Hybridization is discus:ed under Taxonomic Problems below.

Taxonomic Problems The humpback chub was the last fish species to be described from the Colorado River basin (Miller 1946) and is endemic to the basin. The type specimen came from the west end of the Grand Canyon of Arizona, and since that time the species has been collected sporadically in the upper basin. Most specimens come from canyon areas which are difficult to sample effectively, and this may be the principal reason humpback chubs are not collected more frequently. The taxonomy of pure Gila cypha specimens is not difficult, but many specimens which appear to be intermediate in form between Gila

63 cypha and Gila elegans (bonytail chub) are known. These intergrades are of uncertain taxonomic placement and raise the possibility that Gila cypha should be considered as a subspecies of Gila elegans (Holden and Stalnaker 1970). Integrades are also known which appear related to the roundtail chub (Gila robusta robusta). All three types have been collected in the same trammel net with no apparent spatial or habitat separation. Based on an ongoing taxonomic program, Miller has suggested that most of Holden and Stalnaker's intergrade forms are actually Gila cypha (Behnke personal communications). Unfortunately a comparison of the characteristics used by Miller and those used by Holden and Stalnaker is not available. For the purposed of this document, all intergrades are considered to be humpback chubs.

Gaps in Knowledge Because of the apparent highly restrictive habitat requirements of the humpback chub, relatively few specimens have been collected. As a result very little information is available about humpback chub life history. Age and growth, food habits, spawning, larval identification, parasites and diseases, position in the food chain, movements, and general habitat requirements have received little research. Unfortunately, the apparent low abundance coupled with inaccessible habitat makes any research difficult and costly. In addition, the apparent low abundance implies that any significant collecting effort may result in a reduction in numbers and a negative impact on the species.

64 RAZORBACK SUCKER (Humpback Sucker) Xyrauchen texanus (Abbott)

This paper refers to Xyrauchen texanus as the razorback sucker rather than using the common name humpback sucker. Both names are used in the literature, however, the common name razorback sucker is becoming most widely accepted. Using razorback sucker rather than humpback sucker also avoides confusion when talking about the humpback chub.

Present and Past Distribution The razorback sucker was once widely distributed throughout the large river portions of the Colorado River and its tributaries. In the upper basin it was present in the Green River to Green River, Wyoming, in the Colorado River to below Rifle, Colorado, and in the lower reaches of the major tributaries such as the Yampa and Gunnison Rivers (Jordan 1891, Everman and Rutter 1894, Hinckley 1973, Hinckley and Deacon 1968). Present distribution in the upper basin is much the same as it was in the past, except that it is generally absent from areas impacted by large dams. For example, the razorback sucker is absent from Flaming Gorge Reservoir and the cold tailwaters below the dam down to the mouth of the Yampa River (Vanicek, Kramer, and Franklin 1970; Holden and Stalnaker 1975a, 1975b; Kidd 1977; Wiltzius 1976; Armantrout, personal communication). Habitat which may be important for the razorback sucker includes the following river segments: Green River--confluence with Yampa to confluence with Colorado River. Yampa River--Lily, Colorado, to confluence with Green River. White River--immediate vicinity of the confluence with the Green River. Colorado River--Rifle, Colorado, to Lake Powell. Gunnison River--Delta, Colorado, to confluence with Colorado River.

65 Present and Past Abundance Razorback suckers were abundant during the late 1800's and early 1900's and were harvested as a commercial species in large quantities. In addition to a long-term decline beginning in the early part of the 20th century, a more precipitous decline appears to have begun in the late 1960's (Vanicek, Kramer, and Franklin 1970; Holden and Stalnaker 1975a). The razorback sucker is presently rare in collections in all but a very few locations. Evidence of reproduction (immature individuals) is lacking in some areas where it was previously common (McAda and Seethaler 1975, Holden and Stalnaker 1975a).

Habitat Requirements Razorback suckers are generally found in backwater areas or areas of very slow current (Holden and Stalnaker 1975a, McAda and Seethaler 1975, Kidd 1977). They have been collected in faster water, and Jordan (1891) considered them inhabitants of the main channels. Young are seldom found but probably seek out eddies, pools, and other slow water near shore. In the upper Colorado River basin, the razorback is restricted to the lower zone and the lower portions of the intermediate zone. They are seldom found in larger tributaries and have never been reported from smaller streams. For example, they are found only in the lower Yampa River, well below the upstream limit of Colorado squawfish (Holden and Stalnaker 1975b). The razorback sucker appears to grow well in warm reservoirs, but though spawning has been observed, no successful reproduction is known from reservoirs. Spawning has been observed several times in the lower basin reservoirs along shorelines where wave action caused currents. Spawning occurred in March at water temperatures of 14-18C (Douglas 1952). Spawning has also been noted over cobble bars in riffles at the mouth of the Yampa River in 1975 and 1976 by McAda and Seethaler (1975). The activity occurred in May at water temperatures of about 6-10C. They also found ripe fish in a flooded gravel pit near Grand Junction, Colorado (the Walker Wildlife Area), as well as in the Colorado River nearby. Water temperature was

66 17C in the gravel pit and 12C in the Colorado River. As in the lower basin reservoirs, no young were found in the gravel pit although attempts were made to locate them (McAda and Seethaler 1975). The observed spawning areas reported by McAda and Seethaler were all at the head of islands that split the current. Spawning occurred over cobble-sized rocks at depths of two to four feet with current veolcities around 3 fps. Razorback suckers have also been propagated artificially at Willow Beach National Fish Hatchery. Ripe fish were collected from lake Mohave on March 27, 1974, at water temperatures of approximately 16C (Toney 1974).

Foods In its natural habitat, the razorback is a bottom feeder, sucking up plant and animal material along with mud (Vanicer 1967). In reservoirs and perhaps at times in riverine situations, plankton (especially crustaceans) are consumed (Minckley 1973). It appears that the razorback can feed both on the bottom and in the open water. Food of larval stages is unknown in natural conditions, but larval fish were fed on strained beef liver, baby food, and zooplankton under artificial propagation conditions at Willow Beach National Fish Hatchery (Toney 1974).

• Age and Growth The razorback sucker has been documented to reach weights up to 2540 grams and fork lengths up to 587 millimeters (Douglas 1952). No extensive age and growth data has been collected on this species. Kidd (177) reporting data collected by the Colorado Division of Wildlife lists one razorback sucker of 495 millimeters total length at age IX.

Movements Jordan (1891) suggested that razorback suckers may migrate upstream to spawn in the spring, but little conclusive evidence is known for this phenomenon. McAda and Seethaler (1975) reported one tagged female moving upstream approximately 20 miles in two weeks to a spawning site.. This fish moved from the Green River, which is altered by Flaming Gorge Dam, to the Yampa River, which is unaltered.. 67 Predators Predators may include the Colorado squawfish (Ptychocheilus lucius), but a number of introduced species including red shiners (Notropis lutrensis), redside shiners (Richardsonius balteatus), channel catfish (Ictalurus ounctatus), green sunfish (Lepomis cyanellus), and largemouth bass (Micropterus salmoides) are more likely predators of young fish at this time.

Diseases and Parasites No natural diseases have been reported in razorback suckers, but parasitism by anchor worms (Lernaea sp.) is known. Toney (1974) reported that the razorback juveniles being raised at the Willow Beach Hatchery became infected with Ichthyophthirius and Myxosoma.

Hybridization Hybrids between Xyrauchen and Catostomus have long been known. The earliest record is described as Xyrauchen uncompahgre by Jordan (1891). Hybridization in nature between these two genera is discussed more fully by Hubbs and Miller (1953). Until recent years these hybrids have been quite rare, but data presented by Holden and Stalnaker (1975) indicate that the relative abundance of hybrids is increasing.

Taxonomic Problems The razorback sucker is endemic to the Colorado River Basin and is also known as the humpback sucker. Both common names derive from the pronounced nuchal hump which is present in adults. This sucker is distinct from any other living species; the differentiation is of such a magnitude that the species is classified in a monotypic genus (a genus with only a single species). The razorback sucker evidently evolved from the same stock as the genus Catostomus and may have closer genetic affinities to Catostomus than is apparent from gross morphological comparison (Miller 1958). The razorback sucker is readily identified by the presence of a nuchal hump which is pronounced in specimens over 50 mm total length,

68 but is not obvious in smaller specimens. Hybrids with the flannelmouth sucker (Catostomus latipinnis) demonstrate intergrades of the nuchal hump which is not present in the flannelmouth sucker. Larval and early juvenile razorback suckers are difficult to distinguish from other sucker species, and adequate taxonomic keys are only now being developed.

Gaps in Knowledge Additional inventory studies of the razorback sucker distribution and abundance are needed to supplement the discontinuous data presently available. While adequate spawning habitat descriptions are available, spawning no longer occurs in some areas that were once used. It is not known if the microhabitat has changed, if the population has become so reduced that spawning goes unobserved or does not even occur, or if some other unsuspected factor is operating. The relationship of the razorback sucker to introduced species is also unknown and needs to be determined. As with the other large river endemics, the minimum required river size and flow is not known with any degree of precision. While exact figures of river size and flow may be undeterminable, the present possible range of these parameters must be determined more accurately to allow determination of impacts of future projects.

69 BONYTAIL CHUB (Gila elegans) Baird and Girard

Present and Past Distribution The bonytail chub was originally abundant in all the large river habitat of the Colorado River basin, but in the upper basin it is presently known only from the Green River in Utah. It may also occur in the Colorado River in Colorado and Utah. Since one or more of the other large river endemic species (humpback chub, Colorado squawfish, and razorback sucker) is known from these areas (Holden and Stalnaker 1975a, Koster 1960, Kidd 1977) the presence of bonytail chubs is also possible. While no recent documented records of bonytail chubs are known from the San Juan River, Greg Schmitt of the New Mexico Fish and Game Department reported catching them in the upper San Juan River before Navajo Reservoir was formed. The identification of a "pencil thin" peduncle and the fact that the more abundant roundtail chub was also taken appears to verify that the bonytail chub was indeed collected. Habitat which may be important for the bonytail chub includes the following river segments: Green River--confluence with Yampa River to confluence with Colorado River. Yampa River--Lily Park, Colorado, to confluence with Green River. White River--Immediate vicinity of confluence with Green River. Colorado River--Palisade, Colorado, to Lake Powell. Present and Past Abundance Several expeditions near the turn of the century collected bonytail chubs with relative ease and often in considerable numbers, indicating that they were once relatively abundant (Cope and Yarrow 1875, Jordan 1891, Gilbert and Schofield 1898, Chamberlain 1904). Miller (1961) documented the decrease of bonytail chubs in the lower basin from collections made between 1854 and the 1950's. Bonytail chubs became rare and vanished from the lower basin between 1926 and the 1950's. Following the closure of Glen Canyon Dam in 1962, bonytail chubs were common in Lake Powell, but they have steadily decreased in abundance and were seldom found in recen, collections (Utah Fish and Game Department 1974). Vanicek and Kramer (1969) collected 67 bonytail chubs in a study in Dinosaur National Monument during 1964 to 1966. Holden and Stalnaker (1975a, 1975b) found the species to be much less common in Dinosaur National Monument during their studies from 1968 to 1971, a period of only about three years. They noted similar low abundances of bonytail chubs in the Green and upper Colorado rivers as well, and did not observe evidence of reproduction in any of the areas sampled.

Habitat Requirements The bonytail chub is found in the large turbid rivers of the Colorado basin, especially those associated with swift water canyon areas. It is generally collected in eddies adjacent to swift water (Vanicek 1967, Holden 1973). Little is known of the reproduction of bonytail chubs except that, based on ripe fish, spawning occurs at approximately 18C (Vanicek and Kramer 1969). No young bonytail chubs have been found in recent years. No other information was found in the literature on habitat requirements of bonytail chubs.

Foods Adult bonytail chubs are reported to feed primarily on surface debris. Terrestrial insects and plant debris make up a large portion of the diet (Vanicek 1967). No fish were reported from the stomachs of bonytail chubs but fish were present in a significant portion of roundtail chub stomachs. A higher portion of roundtail than bonytail chub stomachs were empty, indicating that the roundtail chub is a more sporadic feeder than the bonytail chub (Vanicek 1967). No food information was found for other life stages of the bonytail chub.

Age and Growth Vanicek (1967) presents age and growth data for the bonytail and roundtail chubs. In his studies the bonytail and roundtail chub species were not separated below 200 mm total length, and both species were used in the growth analyses for each species. In addition, values reported in the text and tables are not in agreement. Movements No information concerning movements of bonytail chubs was found in the literature.

Predators Before the introduction of exotic species, the Colorado squawfish was probably the major predator on adult bonytail chubs. Presently, largemouth bass (Micropterus salmoides) may be a significant predator in addition to the squawfish. Young bonytail chubs have a number of potential predators including the roundtail chub, Colorado squawfish, red shiner (Notropis lutrensis), redside shiner (Richardsonius balteatus), channel catfish (Ictalurus punctatus), green sunfish (Lepomis cyanellus), and largemouth bass. The greatest threat of predation is probably to the larval and juvenile bonytail chubs by the red shiner and redside shiner, as all three species utilize similar habitat.

Diseases and Parasites The only parasites which have been reported for bonytail chubs have been anchor worms (Lernaea sp.) (Vanicek 1967). It is not known if this parasite represents a significant threat to the species, however, the occurrence indicated that it does not.

Hybridization Holden (1968) and Holden and Stalnaker (1970) reported apparent hybridization between the bonytail and humpback chub based on a computer- ized taxonometrics program utilizing meristic characters.

Taxonomic Problems The bonytail chub was first collected in 1851 and named in 1853 (Baird and Girard, 1853). For many years the bonytail chub and the roundtail chub were regarded as subspecies of Gila robusta, but taxonomic work by Holden (1968) and Holden and Stalnaker (1970) demonstrated the position of the bonytail chub as a separate species, Gila elegans. An additional nomenclature problem that arises from the confusion in taxonomy is that in some areas the roundtail chub (Gila robusta robusta) is widely known as the bonytail chub. This is especially true in the lower basin, and much of the older literature reporting bonytail chubs in southern Colorado, Arizona, and New mexico is based on the roundtail chub. Separation of the intergrade forms (Between G. elegans and G. cypha) is difficult in the field, and characterization of larval forms of these species and the roundtail chub is inadequate to effect separations.

Gaps in Knowledge While the bonytail chub is presently known only from the Green River, it may well occur in the mainstem of the Colorado River as well, and inventory studies are needed to establish its exact distribution. A complete description of bonytail chub habitat requirements at various life history stages is also not available. Little information on spawning, age and growth, or food habits of the various life stages has been accumulated, and this information is necessary to prevent extirpation of the species.

73 COLORADO RIVER CUTTHROAT TROUT (Salmo clarki pleuriticus) Cope

Present and Past Distribution The original distribution included cold water streams of the upper basin to the Dirty Devil River in the west and to the San Juan River in the east part of the basin. The range was not continuous because the main Green River below the town of Green River, Wyoming, and the Colorado River below Glenwood Springs historically were not trout habitat. Essentially the distribution of S. c. pleuriticus and the large, main channel species such as squawfish and bonytail chub was mutually exclusive. The only remaining pure populations recognized by Behnke and Zarn (1976) occur in the upper Green River basin of Wyoming in Rock Creek, a tributary of Piney Creek, and in the North Fork of Beaver Creek, a tributary of La Barge Creek, both in Sublette County, Wyoming. Populations exposed to hybridization but wholly typical of pleuriticus phenotype occur in Northwater Creek (Parachute Creek drainage tributary to the Colorado River) and in Cunningham Creek (Fryingpan River drainage tributary to the Colorado River). Areas which presently support phenotypically good examples of pleuriticus and which may be important habitat for the Colorado River cutthroat trout includes the following stream segments: Northwater Creek tributary to East Middle Fork Parachute Creek tributary to Parachute Creek tributary to Colorado River at Grand Valley, Colorado. North Fort Cunningham Creek tributary to Fryingpan River tributary to Roaring Fork River tributary to Colorado River at Glenwood Springs. Douglas Creek, Carbon County, Wyoming, tributary Big Sandstone Creek, tributary Little Snake River, tributary Yampa River. Little West Fork, Sumit County, Utah, tributary Black's Fork tributary Green River. North Fork Beaver Creek, Sublette County, Wyoming, tributary Piney Creek, tributary Green River.

74 Rock Creek, Sublette County, Wyoming, tributary La Barge Creek tributary Green River. Colorado River, Rocky Mountain National Park, Colorado (this population may be extinct). Trapper's Lake, Garfield County, Colorado, tributary White River. Big Sandstone Creek headwaters, Carbon County, Wyoming, tributary Little Snake River, tributary Yampa River. North Fork Little Snake River, Carbon County, Wyoming, tributary Little Snake River, tributary Yampa River. Ted Creek, Carbon County, Wyoming, tributary North Fork Little Snake River, tributary Little Snake River, tributary Yampa River. Soloman Creek, Carbon County, Wyoming, tributary N. Fork Little Snake River, tributary Little Snake River, tributary Yampa River. West Fork Muddy Creek, Uinta County, Wyoming, tributary Muddy Creek, tributary Black's Fork, tributary Green River. Van Tassel Creek, Uinta County, Wyoming, tributary West Fork Muddy Creek, tributary Black's Fork, tributary Green River. East Fork Muddy Creek, Uinta County, Wyoming, tributary Muddy Creek, tributary Black's Fork, tributary Green River. Beaver Dam Hollow, Uinta County, Wyoming, tributary East Fork Muddy Creek, tributary Muddy Creek, Tributary Black's Fork, tributary Green River. Muddy Creek, Uinta County, Wyoming, tributary Black's Fork, tributary Green River. Gilbert Creek, Uinta County, Wyoming. Archie Creek, Uinta County, Wyoming. South Horse Creek, Sublette Coutny, Wyoming, tributary Horse Creek. Macki Creek, Sublette County, Wyoming, tributary Cottonwood Creek. North Fork Muddy Creek, Sublette County, Wyoming, tributary Muddy Creek, tributary Black's Fork, tributary Green River. Spring Creek, Sublette County, Wyoming, tributary Piney Creek, tributary Green River. Trail Ridge Creek, Sublette County, Wyoming, tributary Piney Creek, tributary Green River.

75 Present and Past Abundance No quantitative data is available on the past abundance of the Colorado cutthroat. Habitat decline apparently began with the beginning of mining in the 1850's and hybridization undoubtedly commenced with the first stockings of rainbow trout in the 1880's. No information was found concerning abundances prior to the middle to late 1950's. This, in part, is due to the taxonomic difficulties in separating the native and introduced cutthroats or unhybridized and hybridized native cutthroat. Presumable, past (pre-settlement) abundances were higher in most streams than the present abundances of all trouts. Present abundances are not documented in quantitative measures, but are classed as "common" or "abundant." This is taken to mean that a viable and comparable (to other trout streams of similar size and character) population of Colorado cutthroat is present in the few areas where they are found. In fact, since this species remains only in the most remote, isolated, and, therefore, least disturbed habitat, present abundances in these few locations are probably similar to historical abundances. Present populations probably vary from a few hundred to a few thousand fish at each remaining location.

Habitat Requirements Habitat requirements of the Colorado cutthroat trout appear to be identical with other subspecies of cutthroat trout, and similar to the habitat of most trouts. The cutthroat trouts are generally tolerant of colder waters and higher gradient streams than either the brook or brown trouts and probably also the rainbow trout. They are not as tolerant of warm waters as the brook or brown trouts, but they tolerate high temperatures similar to those tolerated by rainbow trout. They do not appear to have appreciably different food or spawning requirements than do the other trout species, and only minor differences in susceptibility to toxic substances have been observed between the different species. This indicates that hybridization with introduced species is the major factor in the decline of the Colorado cutthroat and implies that if other

76 species were eliminated, all waters suitable for trout within the original distribution of the Colorado cutthroat could be successfully repopulated with the Colorado cutthroat.

Foods No information specific to the Colorado cutthroat is available, but feeding may be assumed to be opportunistic on a wide variety of invertebrates similar to other Salmo clarki subspecies.

Age and Growth While age and growth data have been collected on the Colorado cutthroat, very few collections have differentiated this subspecies from other subspecies with the result that few data can be positively assigned to the subspecies pleuriticus. The most complete data available for pleuriticus are those collected during spawning investigations at Trapper's Lake, Colorado (Snyder and Tanner 1960). Since both the pleuriticus and lewisii subspecies are present in this lake and do not hybridize to a large extent, a comparison is also possible which relates, to some extent, the differences between the more abundant lewisii data and the scarce pleuriticus data. These relationships may not apply in stream habitats, however. In this study pleuriticus were both shorter and lighter at a given age group (up to age group V, the oldest age group found). In these studies, spawning migration information was the primary objective, and only fish in the spawning runs were sampled. Thus little data on juvenile forms was obtained.

Movements Movement information relative to spawning runs may be found in Snyder and Tanner (1960). No other movement information was found, but there is presumably an upstream spawning migration in pleuriticus similar to that found for other S. clarki subspecies.

77 Predators No information was found on the predators on S. c. pleuriticus. Presumably predation is similar to that on other S. clarki subspecies and is not a significant factor in most populations' dynamics.

Diseases and Parasites No information was found on the diseases and parasites specific to S. c. pleuriticus, but diseases and parasite problems are probably similar to those of other subspecies of S. clarki.

Hybridization Hybridization is discussed under Taxonomic Problems below.

Taxonomic Problems Because of extensive hybridization with rainbow trout and non- native cutthroat trout, the Colorado River cutthroat trout, as pure populations, is one of the rarest native fish in the upper basin. S. c. pleuriticus was included in Miller's (1972) list of threatened freshwater fishes of the United States; the Bonneville chapter of the American Fisheries Society considers it endangered (Holden, et al. 1974); it is listed as threatened by the Colorado Division of Wildlife, and it was recommended that pleuriticus be listed as threatened by the U. S. Department of Interior (Behnke and Zarn 1976). Only two known populations in small, isolated streams in Wyoming were considered "pure" pleuriticus by Behnke and Zarn. The cutthroat trout and the Rocky Mountain whitefish are the only native salmonids in the upper Colorado River basin; all others have been introduced. The brown trout has replaced the native cutthroat trout in the larger tributaries and the brook trout has largely replaced it in the smaller tributaries. Massive and continued stocking of rainbow trout and non-native subspecies of cutthroat trout caused hybridization and loss of identity of the native cutthroat trout throughout the upper basin. Fish which resemble native cutthroat trout are not rare in the upper basin, but upon close examination, these trout almost invariably show indications of hybridization (Behnke 1975, 1976a, 1976b, 1977; Behnke and Zarn 1976).

78 A problem making accurate identification difficult is the great variability and overlapping of character values in various subspecies of cutthroat trout. S. c. pleuriticus has no known unique character distinguishing it from all other trout, but rather it shows tends in a series of characters. The coloration may be brilliant, with reds, orange, and yellows emphasized, particularly in mature males. The spots are medium- large, round and pronounced and are located posterio-dorsally. Lateral series scale counts average more than 180 with more than 43 scales above the lateral line. Basibranchial teeth are present in pure pleuriticus.

Gaps in Knowledge The most significant gap in knowledge about the Colorado cutthroat is whether or not other undiscovered isloated populations exist. Because existing populations exist upstream of barriers which block upstream movement of introduced species and in streams without lakes which could have been stocked by airplane, other such locations within the upper Colorado River basin should be investigated. A second major need (though not a gap in knowledge) is to determine where suitable isolated situations exist which could be renovated and restocked with Colorado cutthroat trout. Other gaps in knowledge are related to age and growth and annual surplus production which might be available for angler harvest.

79 KENDALL WARM SPRINGS DACE (Rhinichthys osculus thermalis) Hubbs and Kuhne

Present and Past Distribution and Abundance The Kendall Warm Springs dace was discovered in 1934 and is restricted to Kendall Warm Springs, Sublette County, Wyoming. This warm spring drains into the Green River after flowing several hundred feet and is isolated from the river by a 10-foot high deposit of travertine. Water temperature averages approximately 29C. This species presumeably evolved after isolation from the parental Rhinichthys osculus stock. It is found nowhere else. Present and past distribution and abundance are probably identical.

Habitat Requirements No information is available on food habits of the Kendall Warm Springs dace, but they probably feed opportunistically on small invertebrates as is typical of the speckled dace. The Kendall Warm Springs dace is smaller than the speckled dace from the adjacent Green River, and was reported to reach a maximum length of 44.5 mm in the specimens examined by Hubbs (Hubbs and Kuhne 1937). No age and growth studies have been conducted, but it is likely that growth is more or less continuous throughout the year because of the constant warm temperature. Continuous growth would preclude age determinations and make growth studies difficult. Peak spawning appears to be from late June to early September, but the spawning season may be protracted as compared with the speckled dace because of the constant warm temperature. The sex ratio found by Hubbs and Kuhne (1937) appears to be unequal as there were 201 females to only 50 males in the 251 fish examined. No parasites or diseases have been reported from Kendall Warm Springs dace. Since no other fish occupies the warm spring creek, no predation by fish occurs. Predation by piscivorous birds or mammals has not been reported and is probably insignificant.

80 Taxonomy and Background The Kendall Warm Springs dace differs from the speckled dace (Rhinichthys osculus osculus), from which it is presumed to have evolved, principally in having larger scales. There is little overlap in lateral line scale counts. Other differences between the two species include body proportions, coloration, fin rays, and size.

Gaps in Knowledge While many of the details of the ecological requirements of the Kendall Warm Springs Dace are unknown, it is not presently in danger of extinction. It is considered endangered primarily because of its restricted habitat. Since the entire habitat is under federal control providing adequate protection for the species, no immediate danger is apparent to the species short of the unlikely occurrence of a geologic catastrophy such as the drying up of the Springs. Because the species is of very limited distribution and numbers and the population is stable, major research efforts are unjustified in that they could have a significant impact on the species.

81 The following species are not considered threatened or endangered, therefore, the descriptions are not in as great a detail as the preceding descriptions. These species represent a critical component in the ecosystems of the threatened and endangered species, therefore, their life histories are presented to allow a fuller appreciation of the status of the endangered species.

ROUNDTAIL CHUB Gila robusta robusta (Baird and Girard 1853)

Background The roundtail chub is endemic in the Colorado River basin. A single subspecies is recognized for the roundtail chub in the upper Colorado River basin. In the lower basin, additional subspecies are recognized: Gila robusta seminuda from the Virgin River, G. r. grahami from the tributaries of the Gila River, and G. r. jordani from the Pahranagat Valley, White River, Nevada. All of these subspecies are rare and G. r. 'ordani is listed as endangered under the Endangered Species Act. The other two subspecies are candidates for threatened status. Another chub native to the Gila River drainage and formerly considered as G. robusta should be recognized as a valid species, G. intermedia (Rinne 1969, Minckley 1973). This species is a candidate for endangered status. In the past, the roundtail chub and the bonytail chub (G. elegans) were treated as a single species, and the common names were also used interchangeably. In addition, the roundtail chub has often been confused with the squawfish (Ptychocheilus lucius), which is superficially similar in appearance when young. Thus, previous literature must be interpreted with caution relative to the species referenced. For example, it seems most probable that Bailey and Alberti's (1952) records of squawfish being abundant in the Yampa River at Hayden, Colorado, were actually based on roundtail chub, and that the occurrence of "bonytail chub" in Navajo Reservoir, New Mexico, given by Olsen and McNall (1965), is also based on the presence of roundtail chub.

82 Distributions and Abundances The roundtail chub is still abundant throughout much of the upper basin. Abundance and distribution have been reduced because of environmental modifications and competition from non-native fishes. As with other native Colorado River basin fishes, the roundtail chub lacks the lacustrine adaptations necessary for successful coexistence with non- native fishes in large impoundments. When large reservoirs are created on turbid streams, the roundtail chub may comprise a significant proportion of the initial fish population, but it usually decreases to levels indicating only occasional stragglers within a few years. For example, soon after the filling of Navajo Reservoir, the roundtail chub constituted 19 percent of all fish sampled in 1963-64 (Olsen and McNall 1965). By 1968, the roundtail chub was seldom found in collections (Graves and Haines 1969). The reduction of roundtail chub populations appears to be correlated with the establishment of non-native fish populations, especially predatory non-native fishes. A good example of this is found in the disappearance of roundtail chubs from the Black River, Arizona, after the establishment of smallmouth bass (Micropterus dolomieui) (Minckley 1973). The roundtail chub is presently common in the warm intermediate zone streams of the Colorado River basin except for the main San Juan and its tributaries below Navajo Dam. They are also found in the upper sections of lower zone streams such as the Colorado River above Moab, Utah, and the Green River above Jensen, Utah (Vanicek, Kramer, and Franklin 1970; Sublette 1977; Smith 1976; Holden and Stalnaker 1975a; and Taba, Murphy, and Frost 1965).

Life History and Ecology Idult roundtail chubs have been collected in a variety of habitat types from riffles to backwaters, but they generally favor pools and eddies (Vanicek, Kramer, and Franklin 1970). Juveniles are also found in a variety of habitat types, but they are more common in riffle areas in the lower zone streams (e.g. the Colorado River between Grand Junction', Colorado, and Moab, Utah). Holden (in press) also indicated that roundtail

83 chubs are probably better adapted to riffle-pool situations than to sandy, pool-run situations, and that the juveniles were probably outcompeted by red shiners (Notropis lutrensis) in the stretches of the river with slower current. Roundtail chubs are predominantly carnivorous. They feed on both terrestrial and aquatic insects, and some fish are taken by larger adults. Larger individuals also tend to eat more items floating on the surface such as plant debris (Vanicek and Kramer 1969). Young roundtail chubs tend to feed predominantly on aquatic insects found on the bottom of pools and eddies. The roundtail chub may reach a size of 500-600 mm total length in the larger river environments, but they typically mature at total lengths of 150-200 mm in smaller tributaries. Age and growth and length-weight relationships are reported for the Green River for 1964-1966 by Vanicek and Kramer (1969). In this study, fish less than 200 mm total length were not identified to subspecies, and data for both the roundtail and bonytail chubs (G. elegans) are considered together. Spawning and reproduction of roundtail chubs appears to occur at temperatures of 18.3C (65F) and higher, but no observations of actual spawning have been made and exact spawning locations have not been found (Vanicek and Kramer 1979, Holden 1973). Reproduction is present, however, as indicated by a complete range of size groups (Holden 1973, Sealing et al. 1974). Dotson (1960) reported that leeches were frequently found on chubs collected in the Green River above the mouth of the Yampa River, but the species of chub was not specified. Vanicek (1967) reported finding tapeworms (Proteocephalus sp.) in the stomachs and anchor worms (Lernaea sp.) attached to the fins and gills of roundtail chubs. While no specific information is available which indicates that roundtail chubs are a favored prey species of any other fish, it is highly probable that they are prey for most of the native and introduced carnivorous fish in the Colorado basin. Roundtail chubs of all sizes could have been preyed upon by the larger specimens of the Colorado squawfish reported in the past. Since the roundtail was more abundant

84 in the past, and the introduced forage species such as the red shiner and redside shiner were not present, it is likely that the roundtail chub was a major prey species for the piscivorous Colorado squawfish.

85 PIUTE SCULPIN Cottus beldingi Eigenmann and Eigenmann

Background In 1889, S. S. Jordan collected four sculpins from the Eagle River in Colorado which he named Cottus annae, the Eagle sculpin. Bailey and Bond (1963) considered C. annae as a synonym of Cottus beldingi, the Piute sculpin. Cottus beldingi appears to be rare in the upper Colorado River basin, but, in part, this may be attributed to inexperienced identification. The mottled sculpin (C. bairdi), the species often confused with the Piute sculpin, has palatine teeth and more than one preopercular spine (skin should be dissected to observe spines). C. beldingi lacks palatine teeth (or shows feeble development) and has only one preopercular spine. The range of this species includes the Lahontan and Bsnneville basins and the Columbia River basin including the upper Snake River. It is likely that the Piute sculpin invaded the upper Colorado River basin from the upper Snake River or Bonneville basin after Cottus bairdi was already established. The Piute sculpin was probably blocked from a more general distribution in the basin by competitive exclusion of the sculpin niche by the mottled sculpin, although both species occur together in the Bonneville basin and upper Snake River drainage. Actual specimens of the Piute sculpin (excluding the type specimens) are known only from the Fraser River, Colorado River, Roaring Fork River, Sheephorn Creek, and Blacktail Creek in the Colorado basin. A native species with such a restricted distribution may be a valuable indicator species and more attention should be devoted in future investigations to proper identification of sculpin specimens.

Life History and Ecology Typically an inhabitant of trout streams, C. beldingi may prefer higher gradient streams than C. bairdi (Baxter and Simon 1970). Although typically characterized as a stream fish of fast flowing waters, the Piute sculpin is common in Lake Tahoe of the Lahontan basin. Nothing is known of its habitat characteristics in the upper Colorado River basin.

86 MOTTLED SCULPIN Cottus bairdi Girard

Background The mottled sculpin has a wide distribution in North America east of the Continental Divide, but also is native to the Bonneville basin and certain parts of the Columbia River basin including the upper Snake River. It is widely distributed in the upper Colorado River basin, suggesting that it became established in the basin prior to the invasion of the locally restricted Flute sculpin, Cottus beldingi. In the upper basin, the mottled sculpin typically occurs with trout, whitefish, speckled dace, and bluehead sucker. The large size attained by trout in many streams is often attributed to the forage value of the mottled sculpin.

Life History and Ecology The mottled sculpin's optimum habitat is clear, flowing streams with rocky substrate. Their peculiar morphology and adaptations for life in the substrate makes the sculpin "niche" relatively secure against displacement by non-native minnows and suckers. The mottled sculpin's diet consists mainly of insects, and it may reach six inches in size. An enigma of sculpin distribution in the upper basin is why the mottled sculpin is so generally distributed and the Piute sculpin so restricted.

87 FLANNELMOUTH SUCKER Catostomus latipinnis Baird and Girard

Background The flannelmouth sucker is endemic to the Colorado basin. It was found throughout the intermediate and lower zones of the basin in early studies. The flannelmouth sucker is known to hybridize with the bluehead, white, and razorback suckers (Holden 1973). Present distribution appears to be similar to past distribution except that it has become scarce or absent in large reservoirs (Graves and Haines 1969). The flannelmouth sucker is one of the most abundant species taken in collections from the intermediate zone of the rivers in the basin and often comprises the greatest fish biomass. It is less abundant in cooler headwater streams where it is replaced by the bluehead sucker (Catostomus discobolus). The flannelmouth sucker is also found in small, warm streams.

Life History and Ecology Preferred habitat of the flannelmouth sucker is in the pools and eddies of the main channels of larger streams. They do not often frequent backwaters as adults, but young are usually abundant in those backwaters associated with a main channel. Young are not common in sluggish, very warm areas, but have been reported as common in pools and slow runs (Holden and Stalnaker 1975a). Food habitat studies by Taba, Murphy, and Frost (1965) revealed primarily bottom materials in flannelmouth sucker stomachs. The flannelmouth sucker has been observed feeding on and between rocks in shallow riffles. Larvae probably feed on crustaceans and small aquatic insects much as most other sucker species do. Flannelmouth suckers spawn in late spring when water temperatures reach about 13C. Ripe females were found until late June and ripe males were found until early August in the Echo Park area of Dinosaur National Monument (Holden 1973). These fish were found in 3-4 feet of water over a gravel substrate in the upper Yampa River. As the spring runoff passed, this area became a riffle. McAda and Seethaler (1975) also

88 observed flannelmouth suckers on a gravel riffle in the lower Yampa River. Bosley (1960) reported flannelmouth suckers as large as 513 mm total length and weighing 1332 g from the Flaming Gorge before impoundment. McDonald and Dotson (1960) provide some age and growth data. They found flannelmouth suckers as old as age group VI with total lengths averaging 363 mm. Dotson (1960) noted large open sores on adult flannelmouth suckers in the vicinity of Green River, Wyoming, and attributed their cause to pollution from the town of Green River. External copepod parasites (Lernaea sp.) are commonly found on flannelmouth suckers. A relatively high percentage of flannelmouth sucker adults in collections are blind in one or both eyes, but the blindness does not appear to affect the fish. As a result of its abundance and wide distribution in the Colorado River basin, the flannelmouth sucker is a major forage species for native and introduced piscivorous species in the upper basin. It is not known if the introduction of exotic piscivorous species has affected flannelmouth sucker populations, but available information suggests that flannelmouth sucker populations have not decreased since historical times.

89 MOUNTAIN WHITEFISH Prosopium williamsoni (Girard)

Background The mountain whitefish has a widespread distribution in western North America. It is native to the Green River drainage of the Colorado basin, but not to the Colorado River proper. It has been established in the Roaring Fork River, a tributary of the Colorado River in Colorado. The whitefish is locally popular as a game fish in some areas such as the upper Yampa River. It is not common in any impoundments in the upper basins but is still relatively abundant throughout most of its original range in moderate to large triburary streams (e.g. upper sections of the Yampa, White, and Green rivers).

Life History and Ecology The whitefish feeds mainly on aquatic insects and its preferred habitat is open, slow run areas of cool, tributary streams of the upper basin. The upper limits of whitefish distribution may overlap the distribution of brown and rainbow trouts. They exist further downstream than trout and are found in warm waters (to about 75-80F). Because of their tolerance of warmer water and a habitat preference of open, riffle areas, whitefish have not suffered from loss of habitat (destruction of riparian vegetation and rip-rapping of banks) comparable to that of trout species. Whitefish typically attain a maximum size of 2-3 lbs. The largest size in the upper basin is found in the introduced population in the Roaring Fork River, Colorado. Some of the early references to "grayling" probably were based on the mountain whitefish. The whitefish must have been an important component of the native fish fauna in the Green River basin and was probably a dominant fish in the transition area between the trout zone ( 7000 ft) and the sucker zone ( 5000 ft). Present non- native fishes competing with the whitefish would be the redside shiner (Richardsonius balteatus) and the white sucker (Catostomus commersoni).

90 SPECKLED DACE Rhinichthys osculus yarrowi (Girard)

Background Jordan (1891) indicated the speckled dace was abundant in small streams in the mountains, less common in larger streams, and rare below the mountains. This general distribution was also noted by Vanicek, Kramer and Franklin (1970) and by Holden and Stalnaker (1975a, 1975b). They found the species most abundant in the intermediate zone of the upper basin ecosystem and much rarer in the larger and warmer rivers. There is no apparent difference between historical distribution and abundance and the present distribution and abundance of the speckled dace except that it has become much rarer below large dams where the habitat is drastically altered (Vanicek, Kramer, and Franklin 1970; Wiltzeus 1976; Sublett 1977).

Life History and Ecology Speckled dace are generally found in habitats associated with swift current and rocky substrates. While they are usually considered riffle fish, they are often found in pools or eddies at the bottom of riffles. Young dace are usually found in quieter waters than adults. Speckled dace are omnivorous as adults (Minckley 1973). Holden (in press) suggested juveniles may be more carnivorous than adults, which is common in omnivorous species. No information on reproduction was found. Natural predators of speckled dace were probably the roundtail chub and the Colorado squawfish. Presently, all omnivorous or piscivorous exotic fishes in the Colorado basin probably prey on the speckled dace.

91 MOUNTAIN SUCKER Catostomus platyrhynchus (Cope)

Background The mountain sucker is native to streams of the Great Basin in Utah, Nevada, and California; North Fork Feather River, California; headwaters of the Green River drainage in Utah Wyoming and Colorado; parts of the Columbia River drainage in Wyoming, Idaho, Washington, Oregon, and British Columbia; and the upper Missouri drainage (Smith 1966). This species predominated in smaller, cooler headwater streams of the Green River basin. In the warmer, larger streams of the Green River basin, the mountain sucker is replaced by the bluehead sucker. The mountain sucker is relatively common in Wyoming and in the streams draining the northern Wasatch and the Uinta Mountains of Utah, but is known only from the Piceance Creek basin tributary to the White River and Trout Creek tributary to the Yampa River in Colorado. This distribution in the upper Colorado basin is identical with the known historical distribution. It is generally found over rubble bottoms in moderate to swift current of small streams. It is occasionally found in lakes, but lacustrine habitat is apparently not optimal.

Life History and Ecology Food consists of algae, diatoms, and aquatic invertebrates. Maximum lengths are approximately 175 mm total length. Spawning occurs during late spring or early summer. Nothing is known of diseases or parasites attacking this species. Predators on mountain suckers are probably primarily introduced species at present. Historically, the roundtail chub was probably the major predatory of mountain suckers.

92 BLUEHEAD SUCKER Catostomus discobolus Cope

Background The bluehead sucker is native to the upper basin. Below Grand Canyon, the bluehead sucker is replaced by the desert sucker (Catostomus clarki). In the Green River tributaries in Wyoming, the bluehead sucker is rare, and its niche appears to be occupied by the mountain sucker (Catostomus platyrhynchus) (Baxter and Simon 1970). The bluehead sucker is known to hybridize with the flannelmouth and white suckers (Holden 1973). The bluehead sucker has two morphotypes in the upper basin, a "wide" and a "narrow" peduncled form, and intergrades are also known (Vanicek 1967, Holden 1973, Prewitt 1976). Both types have often been collected together, but only subtle differences in habitat preference are apparent.

Life History and Ecology The bluehead sucker is rather highly restricted to areas of rock or gravel substrate (Vanicek 1976, Holden and Stalnaker 1975a) although it has been found in areas of sand substrate in late winter (Holden, personal communication). Young bluehead suckers are found in slower water such as backwaters and eddies along with juveniles of most other native species (Vanicek 1967, Holden 1973). The subgenus (Pantosteus), to which the bluehead sucker belongs, is uniquely adapted for scraping periphyton from rocks. The bluehead sucker apparently feeds by scraping such material. Prewitt (1976) and Taba, Murphy, and Frost (1965) found algae to be the most abundant material in bluehead sucker stomachs. Holden (1973) found ripe male and female bluehead suckers in June and July in the upper Green and Yampa Rivers in his 1968 to 1970 studies. He suggested they spawn when temperatures are about 15-18C. The bluehead sucker is undoubtedly a major forage species for piscivorous fishes in the areas where it occurs. Since its abundance does not correspond with that of the Colorado squawfish, it probably did not serve as a major food item for squawfish in historical times. Present predators are largely introduced species and the roundtail chub. 93 IV. RIVER BASIN DESCRIPTIONS

Thus far we have discussed many aspects concerning the aquatic ecosystem of the upper Colorado River basin, including: the abiotic environment, the biotic factors, and detailed discussions of the important fish species. The upper Colorado River basin is comprised of numerous drainages each with its own character, resources, and potential for development. This section presents a more detailed description of the major basins and concentrates on those aspects peculiar to each. Included within each basin description is the distribution of important fishes. Please note that section III (Species Descriptions) presents distribution data for each species as accurately and as detailed as the literature would allow, and should be referred to for inclusive distribution analysis. Each basin description is organized according to the following outline:

BASIN DESCRIPTIONS OUTLINE

GENERAL A. Location B. Size C. Subdrainages D. History E. Physiography F. Climate G. Land Use H. Geology I. Water Sources and Quality J. Water Quality K. Native Vegetation

FISHES

A. Historical Native (including distribution) B. Present Native (including distribution) C. Introduced D. Known Spawning Habits (location, runs) E. Other Evidences of Reproduction (juveniles, etc.) F. Specific Effects of Water Quality Changes (including temperature)

94 ACTIVITIES IMPACTING FISH

A. Present 1. Mineral 2. Agricultural a. General b. Existing Dams and Diversions 3. Industrial 4. Recreational B. Future 1. Project Developments 2. Impacts on Native Fishes

95 YAMPA RIVER BASIN

General The Yampa River basin is located in northwest Colorado and south- central Wyoming and encompasses an area of 9,530 square miles. It drains Moffatt, Routt, Rio Blanco, Garfield, and Grand counties in Colorado, and Carbon and Sweetwater counties in Wyoming. The drainage basin is 128 miles long in an east-west direction and 75 miles from north to south. It is bounded on the north by the Red Desert, on the east by the continental divide, and to the south by the divide separating the Yampa and White River basins. The Yampa headwaters in the Park Range and flows westerly 128 miles to join the Green River in Echo Park, Dinosaur National Monument. The Yampa drains six percent of the land in Colorado and three percent of the land in Wyoming. Major tributaries of the Yampa include the Little Snake River, Elkhead Creek, Vermillion Creek, the Williams Fork, Trout Creek, and Oak Creek. Settlement began in 1876 when Colorado became a state, the Ute Indians were removed from the Meeker area, and gold was discovered at Hans Peak in Routt County. In 1913 with the advent of reliable transportation in the form of the Denver, Salt Lake, and Pacific Railroad, an influx of homesteaders flooded the Steamboat Springs and Craig areas. Agriculture is the main land and water using industry. Major urban centers are Steamboat Springs in Routt County, and Craig in Moffat County. Climatic conditions vary with elevation from arid desert in the lower basin to cold, humid, alpine zones along the continental divide. The eastern boundary of the basin reaches crest elevations of over 12,400 feet while the valley floor at Echo Park is about 5,000 feet in elevation. The annual temperature ranges from -48C to 38C. Average annual precipitation varies from 40 inches along the continental divide to less than nine inches in the desert areas. The annual frost-free period varies from less than 102 days in the upper basin to 125 days in the lower basin.

96 Most of the Yampa River basin lies within the southern part of the Wyoming basin physiographic province, a plateau area underlain by widespread deposits of relatively soft sedimentary rock and bordered by abrupt mountain slopes and ridges. The Park Range and White River plateau areas are the location of the headwaters for most of the major streams. The most outstanding feature of the Wyoming basin province is the spectacular canyons cut to depths of 3,000 feet by the Green and Yampa Rivers. The Green River flows southward through Lodore Canyon, and the Yampa River flows westward through Bear Canyon to their confluence at Echo Park in Dinosaur National Monument. Almost the entire basin is used for some form of agricultural production. Primary land uses are grazing, timber production, irrigated or dryland crop production, and recreation. The irrigated cropland occupies less than two percent of the land area. Almost all of the irrigated cropland is used for pasture or winter feed production for livestock. Climatic conditions, such as a limited growing season, make the land resource better suited for livestock production than cash crop production. Approximately 85 percent of the land in the Yampa River basin is used for grazing by domestic livestock and wildlife. Commercial timberland, primarily spruce-fir, occupies six percent of the basin and is located in the eastern portions. Public lands furnish about 46 percent of rangeland grazing for domestic livestock, most of the range and habitat for big game and wildlife, and most of the outdoor recreation. The Yampa basin is famous for its mountain scenery, and recreation is a major resource of the basin. The basin offers a variety of scenic wilderness opportunities; and fishing, boating, hunting, skiiing, guest ranches, hiking, and camping attract many tourists. Most of the water yield is produced by melting of the snowpack on the high mountain slopes. Summer precipitation adds little to the water supply. There is a considerable variation in watershed yield, reflecting climatological differences throughout the basin. The Yampa mainstem provides 74 percent of the water supply; 24 percent of the water is produced by the Little Snake, and two percent is produced by Vermillion Creek. Snowfall varies from an average of 160 inches at Steamboat Springs to about 30 inches at Echo Park. Floods are of short duration and low total water production, but peak flows are high. Evaporation losses from ponds and reservoirs range from 17 to 20 inches per year depending on location. There are 87 natural lakes and 111 small reservoirs developed for recreation, fishing, stock water, and irrigation within national forest boundaries, and about 5,500 small reservoirs on other lands used for irrigation, fishing, stock water, and recreation. No large impoundments exist on the Yampa River. The water quality of the Yampa River is high because the clean, clear, high elevation headwaters yield most of the water, while the lower elevation, intermittant streams produce most of the dissolved solids and suspended sediment that leave the basin. Industrial and human pollution has been limited, and base flows have not been significantly depleted. The natural vegetation of the Yampa River basin includes a number of grasses, forbs, and shrubs, depending on the climate and soil. The general acidity and salinity of the salt desert zone limits plants of the upland to: mat salt bush, Gardner salt bush, shadscale, fauning salt brush, bird sage, galleta grass, Indian rice grass, and black sagebrush. Lowlands have greasewood, rabbitbrush, big sagebrush, salt- grass, alkali sacatoon, and western wheatgrass. In the transitional foothill zone, cover is primarily big sagebrush, with pinyon pine, Utah juniper, mountain mahogany, and a variety of grasses. Native plant cover in the mountain zone is a luxuriant combination of grasses, forbs shrubs, and aspen trees. The forests are primarily spruce-fir types. An epidemic of Englemann spruce beetle in 1948 killed most of the merchantable spruce.

Fishes Four of the six threatened or endangered fishes have been found in the Yampa River basin in the past, but only the Colorado squawfish (Ptychocheilus lucius) and humpback chub (Gila cypha) are presently found above the lowest reaches of the river. The bonytail chub (Gila .t.l_e_aans) and the humpback sucker (Xyrauchen texanus) have been collected

98 in the lower section of the Yampa River in Dinosaur National Monument or in the Green River at the mouth of the Yampa (Holden and Stalnaker 1975b; Seethaler, McAda, and Wydoski 1976; Behnke personal communications). Other native fishes found in the basin include the mountain whitefish (ProsoRium williamsoni), roundtail chub (Gila robusta robusta), speckled dace (Rhinichthys osculus), flannelmouth sucker (Catostomus latipinnis), bluehead sucker (Catostomus discobolus) and the mottled sculpin (Cottus bairdi). These other native fishes are common to abundant within their preferred zone within the basin. (For a detailed description, life history, and distribution of each species, refer to Section III - Species Descriptions.) A number of exotic species have been introduced into the Yampa River. Some of these species have established reproducing populations and have become abundant. Included are the redside shiner (Richardsonius balteatus), the fathead minnow (Pimephales promelas), the carp (Cyprinus carpio), the white sucker (Catostomus commersoni), the channel catfish (Ictalurus punctatus), and, in some areas, the sand shiner (Notropis stramineus). Other introduced species have become established but have not become common or are periodically reintroduced such as the rainbow trout (Salmo gairdneri). While spawning is suspected in the lower reaches of the Yampa River - within Dinosaur National Monument, no juveniles of the rare large river endemic species have been found in the river. Only the Colorado squawfish and humpback chub have been found upstream of Dinosaur National Monument. These species have been collected as far upstream as the mouth of Milk Creek about 18 miles below Craig, Colorado, and in Cross Mountain Canyon, respectively (Holden and Stalnaker 1952a and 1975b). Because all collections prior to 1977 had been made during the spawning season, it was assumed that the presence of squawfish in the Yampa River was due to spawning migrations. The collection of squawfish by Prewitt in April, 1977, at Maybell, Colorado, however, indicates that a resident population of squawfish may exist in the Yampa River. At the present time there Is no evidence of reproduction in these middle reaches of the Yampa River, but the possibility of a resident reproducing population must not be

99 discounted. Continuing investigations by Prewitt and Wick for the Bureau of Land Management should contribute additional data on rare fish distribution in the Yampa River much more accurately in the near future. Specific effects of water diversions and associated temperature changes on fishes of the Yampa River are unknown. Effects of channel stabilization (in some areas) and irrigation return flows also have not been investigated.

Activities Impacting Fish Petroleum, natural gas, coal, and sand and gravel are the most important natural resources being developed currently in the basin. Most of the oil and gas development has been in Moffat County, Colorado. Oil and gas produced in the basin is largely exported to Wyoming and Utah by pipeline. Exploration for new oil fields has declined recently, and a resurgence in coal mining due to the demand of steam electric generating facilities is developing into a new industry in the basin. The coal resources of the basin are located mainly in the Yampa coal field in Routt and Moffat counties, Colorado. Most of the coal is of high-volatile C bituminous rank and is low in ash and sulfur content. Relatively little metalic mineral mining has occurred in the Yampa basin. Placer gold has been recovered on the Little Snake; alluvial sands and gravels contain placer deposits in several areas of Moffat County, particularly north of Lay, Colorado. Uranium is widespread throughout the basin, occurring mainly in the Browns Park formation. The mineralization is low grade, but mining has been substantial. Past impacts of these activities on fishes of the Yampa River is unknown, though some impacts probably have occurred. Similarly, agricultural activities must have had impacts on the fishes through diversions and return flows, but no documentation is available. Major impacts to fishes in other upper Colorado River streams appear related primarily to large dam construction which has not occured on the Yampa River. In fact, the Yampa River's mitigation of the effects of Flaming Gorge Dam on the Green River may be the only reason that the lower Green River Still supports rare fish at this time (Holden and Stalnaker, 1975b).

100 It appears likely that no major impacts to the fishes of the Yampa River have occurred, primarily due to lack of major developments in the basin. The Yampa River basin is one of the most rapidly developing areas in the upper Colorado basin. This development is related primarily to national energy requirements and involves coal, oil, and gas prospecting and development. Electrical power generation utilizing mine-mouth plants is rapidly expanding, and government-sponsored water developments of major proportions are currently proposed. Recreational development based on winter sports and corollary residential and seasonal housing is also increasing at a rapid rate. Future predictions of the magnitude of development are always speculative, but it seems inevitable that development in the Yampa basin will increase progressively for several decades. These developments will have effects on the Yampa River to a greater or lesser extent. Such developments as electric generation facilities, recreational housing, and agricultural water development may result in major depletions of water in the river. Historical evidence indicates that the latter two will almost certainly produce significant reductions in water quality as well and are subject to much less governmental control than are power generation facilities. Coal, oil, and gas production are relatively well regulated as to environmental impacts; and in addition, they are likely to have relatively little effect on the Yampa River unless they are located in or immediately adjacent to it. The principal impact will be associated with population increase which results from importing an additional labor force into the area. Undoubtedly the major impact on rare native fishes of the Yampa River basin lies with the proposed agricultural water development, specifically, the Juniper Springs project on the Yampa River and the Savery-Pothook project on the Little Snake River. The Juniper Springs project would inundate a major portion of the Yampa River in an area where the Colorado squawfish is known to occur. Cold water releases and depletion of Yampa River flows would unquestionably have significant adverse effects on the Yampa and Green rivers. In fact, it is almost a certainty that, if the two Juniper Springs project dams were constructed, the effect would be to eliminate the major spawning habitat in the Green

101 River for the Colorado squawfish and the razorback sucker. While less is known of the required habitat for the bonytail and humpback chubs, these two species also utilize approximately the same locations as the squawfish and razorback sucker. The humpback chub has been collected in the area to be inundated by one of the dams. Thus, it is likely that the Juniper Springs project would contribute significantly to, and might even be a major cause of the extinction of the four threatened or endangered large river endemic species in the upper Colorado basin. The Savery-Pothook project would have a less direct effect on the Yampa River, but could cause significant changes in water temperatures, salinities, and stream morphologies in the lower Yampa River and the Green River downstream of Dinosaur National Monument. The draft environmental impact statement for this project (Bureau of Reclamation 1976) provides no assurances in the data contained therein that major temperature changes would not occur in the Yampa River. Since the Yampa River appears to be critical in the maintenance of spawning temperatures in the Green River, lowered temperatures in the Yampa River would be critical. Both projects propose flood control as a beneficial impact. While this impact may be beneficial to recreational and farming development, it is in all probability highly detrimental to the survival of the large river endemic fish species. Floods and high water conditions create and maintain the backwater and cut off areas of rivers in which the young and juveniles of the large river endemic fishes are found. Thus, flooding may be a critical factor governing surviva; of these fishes, and the Prevention of flooding may mean the loss of those species that rely on IT. GREEN RIVER BASIN

General The Green River basin begins just southeast of Grand Teton National Park in Wyoming and extends south to the Colorado River basin in Utah. The Yampa and White rivers in Colorado and Utah are also part of the Green River basin; but, because of their size and importance to threatened and endangered fishes, these two basins are discussed separately. Other major tributaries to the Green River are covered in this discussion and include Blacks and Hams forks in southwestern Wyoming, and the Price, Duchesne, and San Rafael rivers in eastern Utah. The Green River is the largest tributary to the Colorado River. It has a length of about 730 miles and drains an area of approximately 45,000 square miles. The Green River drains a larger area but has a slightly smaller flow than does the Colorado River at the confluence of the Green River and Colorado River. Settlement within the Green River basin began at about the end of the fur-trapping era in the late 1840's. Early settlement was primarily mining-related, but ranching and farming soon followed. Most of the present irrigation systems were constructed prior to the 1920's. The Green River basin exhibits a diverse physiography, ranging from high alpine mountainous areas to low deserts. Most of the basin can be characterized as a high, arid plateau intersected by higher mountain ranges and deeply dissected by major drainages. Where the major drainages cross the intersecting mountain ranges, deep canyons result. As expected, climate varies widely within the basin in response to elevation and proximity of mountain ranges. Temperature extremes of 42C to -48C have been recorded. Annual frost-free periods vary between less than 70 days at the higher elevations to over 130 days in the lower desert regions. Annual precipitation shows a similar wide range of from greater than 40 inches on the west slopes of the high mountains to less than six inches in the desert lowlands. The climate is an important factor in the economy of the Green River basin. Because of low rainfall and short growilg seasons, most areas in the basin are suitable only for livestock grazing. Areas suitable for irrigation are largely limited to forage crops or small grains because of the short growing season and high water stress that results from the nearly constant warm, dry winds during the growing season. Because of the highly dissected topography which makes irrigation impractical in large sections of the basin, large areas are undeveloped and unpopulated. Even grazing is limited in these areas by the low annual production resulting from low rainfall. Geology of the Green River basin is predominantly sedimentary except in the areas of recent mountain building where igneous intrusives are present. A wide range of sedimentary deposits are present ranging from Mississippian limestone and shales to Quarternary aluvial deposits. Consolidated igneous deposits date from the most recent mountain building activity. It is believed that the Green River basin was developed as a north drainage into the North Platte River (and thence eventually to the Gulf of California), and a south drainage into the ancestral Colorado system. The divide between the north and south basins was the Uinta mountain range until sinking of the east end of the range allowed the south basin drainage to capture the north basin stream and the present drainage system resulted (Hansen 1969). The variations in areal geology result in variations in water quality. Headwater areas are characterized by calcium or calcium- magnesium bicarbonate waters of low dissolved solids. Further downstream in more arid areas, dissolved solids increase greatly, and the ionic composition is dominated by sodium and sulfate. Salinities are a major problem in the lower basin. Native vegetation varies from coniferous forests in the headwater areas to large-river riparian cottonwood communities in the lower reaches of the river. The introduced salt cedar (Tamarix pentandra) is also abundant in the lower reaches. Because much of the Green River flows through canyons, a sharp differentiation in vegetation is common near the river. Sagebrush desert and bunchgrass plateaus are found adjacent to the canyon areas in the middle and lower reaches of the river. Soils

104 vary from acid to alkaline in downstream progression from the headwaters, and low sand dunes are found in the desert areas in southern Wyoming.

Fishes Historically, native fish populations in the headwaters of the Green River were primarily Colorado cutthroat (Salmo clarki pleuriticus) (the Wyoming strain), mottled sculpins (Cottus bairdi), mountain whitefish (Prosopium williamsoni), and speckled dace (Rhinichthys osculus). The Kendall Warm Springs dace (Rhinichthys osculus thermalis) evolved in and was limited to Kendall Warm Springs and the short length of the stream between the springs and the river. Further downstream were found mountain sucker (Catostomus platyrhynchus), bluehead sucker (Catostomus discobolus), flannelmouth sucker (Catostomus latipinnis), roundtail chub (Gila robusta robusta), bonytail chub (Gila elegans), humpback chub (Gila cypha), Colorado squawfish (Ptychocheilus lucius), and razorback sucker (Xyrauchen texanus). A considerable number of other species have been introduced into the Green River, and many of the introduced species are now common. Among those introduced species which have become common are rainbow trout (Salmo gairdneri), brown trout (Salmo trutta), Yellowstone cutthroat (Salmo clarki lewisi), brook trout (Salvelinus fontinalis), Utah chub (Gila atraria), redside shiner (Richardsonius balteatus), fathead minnow (Pimephales promelas), carp (Cyprinus carpio), red shiner (Notropis lutrensis), Creek chub (Semotilus atromaculatus), white sucker (Catostomus commersoni), channel catfish (Ictalurus punctatus), and black bullhead (Ictalurus melas). Other species occasionally found in the drainage include largemouth bass (Micropterus salmoides), smallmouth bass (Micropterus dolomieui), green sunfish (Lepomis cyanellus), northern pike (Esox lucius) and walleye (Stizostedion vitreum vitreum). At the present time, all of the native species are still found in some part of the watershed though, in most instances, abundances and/or ranges of native fishes have been much reduced. For example, all of the Colorado basin large-river endemic species have been eliminated from the Wyoming portion of the Green River basin by Flaming Gorge Dam. While

105 reductions in abundance are apparent in most areas as indicated by reduced catches during collecting efforts, no quantitation of the degree of reduction is available. Even tliough all of the large-river endemic species have been reduced in abundance and distribution, the reductions in other sub-basins of the upper Colorado basin appear even more severe. The result is that the Green River below the mouth of the Yampa River comprises the best habitat still available in the upper basin to these rare species. Most of the headwater species in the Green River basin have a distribution and abundance similar to their historical situation. The major exception is the Colorado cutthroat, which is absent as a pure strain except in several isolated headwater areas. As in other sub- basins in the upper Colorado basin, this species has been reduced as a pure strain primarily by hybridization with other introduced cutthroat subspecies and rainbow trout. The Kendall Warm Springs dace, which is limited to Kendall Warm Springs and the short length of stream between the spring and the Green River, is probably present in approximately the same numbers as it was in historical times. Because of the extremely limited habitat utilized by this subspecies, changes in population level or distribution can be readily observed. No significant changes have occurred in this habitat since historical times, and since the habitat is government-owned and protected, future changes are not anticipated. Historically, all of the large-river endemic species presumably spawned throughout their range. Presently, spawning by these species is known in the Green River basin only in the reach from Jensen, Utah, to the mouth. The presence of Colorado squawfish in the Yampa and White rivers at considerable distances above their mouths and at other than spawning times suggests a resident population in these streams and implies that spawning occurs in these rivers as well as in the Green River. Past spawning runs of the Colorado squawfish occurred as far upstream as 30 miles above Green River, Wyoming. For some time after construction of Flaming Gorge, large numbers of Colorado squawfish were reported to

106 accumulate at the dam in their apparent attempt to migrate upstream. Past spawning runs of other large-river endemics are undocumented. Present spawning runs are speculative and undocumented for any of the large-river endemics. The elimination of spawning or resident populations of these species between Flaming Gorge Reservoir and the mouth of the Yampa River is apparently caused by low summer discharge temperatures. The effects of diurnal fluctuations in flow and introduction of exotic species are undocumented, but most knowledgeable professionals believe they are very significant.

Activities Impacting Fish The major activities in the Green River basin which have an impact on the river are energy production, mining, and agriculture. Because of the relatively unfavorable growing conditions in the northern basin, agriculture has relatively little direct impact, though some water is diverted out of the basin. Coal, oil, and trona production within the basin have not had a large impact on the river; the construction of large storage reservoirs for hydroelectric power production with their associated dams has been the major impact in the upper basin. Two major impoundments have been built on the Green River. Fontanelle Reservoir is located about 48 miles northwest of Rock Springs, Wyoming, and is an 8,058-acre impoundment at normal pool elevation. Flaming Gorge Reservoir is located 42 miles south of Green River, Wyoming, and about 11 miles upstream of Bridgeport, Utah. Flaming Gorge Reservoir is about 42,000 surface acres at normal pool elevations and extends upstream nearly to Green River, Wyoming. Both of these reservoirs have profound influences on the flow and water quality in the Green River. Peak flows are much reduced over preimpoundment levels, and both temperature and turbidities have been drastically reduced during summer months. These large impoundments have prevented summer water temperatures below the dam from increasing to levels high enough to permit spawning by the rare and endangered fish species. In addition, they have changed the downstream habitat to favor introduced salmonid species which compete With the native species, and have caused major unnatural diurnal fluctu-

107 ations in flows (because the hydroelectric plants are operated as peaking plants). The threatened and endangered species in the Upper Colorado basin require large river habitat and have disappeared from impoundments, probably because they cannot compete with introduced lacustrine-adapted species and because they do not find suitable spawning habitat in impoundments. Thus the construction of Flaming Gorge Reservoir has eliminated threatened and endangered fishes from approximately 120 miles of the Green River, and has probably affected the suitability of an additional 50-60 miles of the river below the confluence with the Yampa River. While the construction of Fontanelle Reservoir has similar effects on the river, the reach that it affects was not known to be suitable for rare fishes before construction, and its impact on rare fishes has probably been small. Modification of Flaming Gorge penstocks scheduled in 1978 may raise river temperatures enough to allow some large-river endemics to repopulate some of the Green River that is presently unsuitable. The sewage effluent from Green River, Wyoming, previously had an effect on fishes in the Green River (Dotson 1960). With the elimination of much of the native fish population after closure of Flaming Gorge Reservoir, and the dilution effect of the discharge by the reservoir, the effect of the sewage effluent on native fishes at this time is probably slight. Downstream of the effects of Flaming Gorge Reservoir (which are identifiable to approximately Jensen, Utah) to its mouth, the Green River runs through undeveloped areas and it is often isolated from much of man's influence by deep canyons and lack of major tributaries. There appear to be no major man-induced impacts to this lower reach of the river; indeed this reach of the Green River is probably very much like it was in pre-settlement, historical times except for lowered peak flows. Future development in the Green River basin will involve extensive water development. The majority of agriculture in the basin is dependent on irrigation. Dry land farming is already practiced on nearly all of the land which is suitable, and any future increases in crop production will depend on increased availability of irrigation water. In addition to agriculture, energy development is increasing within the basin, and will also require relatively large quantities of water. While both agriculture and energy development have the potential for releasing toxic substances and adding sediment to the streams, depletion of stream flows is expected to exert the greatest impact on the aquatic habitat. As a corollary to energy development, large population increases are expected within the basin. Population increase results in further consumptive water use as well as serious impacts of domestic sewage disposal and large increases in sediment in streams associated with business, housing, and road construction. Energy development within the basin is expected to occur primarily in the lower section in Utah and in southwestern Wyoming. Energy sources which may be developed include primarily coal and oil shale, but significant amounts of uranium also exist and could be developed. The only energy source of significant size under active development at this time is the coal deposits in southwestern Wyoming. Plans for oil shale and uranium development are too nebulous at this time to allow accurate predictions of their effects on the basin as a whole. Similarly, water storage projects associated with irrigation are only in the preliminary stages of planning. In each case, a number of alternative development schemes are proposed, but final choices have not been made. Because the alternatives vary significantly in magnitude and probable impact, accurate determination of impacts on rare fishes would not be possible at this point even if all habitat requirements of the rare fishes were known. The only impact that is certain to occur under any of the possibilities is the reduction of flows in the Green River. The magnitude of reduction possible ranges from minor to substantial. If all of the proposed development were to occur (including the development proposed for the Yampa and White rivers), it is virtually certain that serious negative impacts to the rare fishes would occur. In fact, since past limited water development has already placed the large-river endemic species under severe stress and caused significant reductions in both abundance and range, a major amount of future development is almost certain to entirely eliminate the remaining populations of these species.

109 Present reductions in the abundance and range of the large-river endemics are sufficiently severe that concern is expressed by most professionals over such small changes in habitat as the elimination of a single small backwater known to be a nursery area. Actions on this scale could easily be accomplished by county highway department, cities, or even individual ranchers. Because the Green River basin is the last river system to show changes in population of these rare species, it is presumably the best remaining habitat. As such, changes by man's activities should be more limited than changes that might be tolerated in areas where the large-river endemics have already been extirpated.

110 WHITE RIVER BASIN

General The White River basin is located in northwestern Colorado and east- central Utah. The basin is approximately 107 miles long, 35 miles wide and encompasses an area of 3,808 square miles. The White River headwaters on the north side of the White River Plateau and Flattops mountain range and flows generally west into Utah where it joins the Green River near Ouray, Utah. Drainage is from parts of Moffat, Rio Blanco, and Garfield counties in Colorado, and from Uintah county in Utah. Major tributaries are the South Fork, Piceance, and Douglas creeks in Colorado and Two Waters Creek in Utah. Settlement began in the basin soon after the signing of the 1868 treaty with the Ute Indian tribes and occurred primarily in the river valley and some higher meadow areas where water for irrigation was easily obtained. Livestock grazing operations and their associated irrigated hay production have been the basis of the agricultural economy of the White River Basin since the early settlement period. Timber production was also an important agricultural activity from early settlement until the Englemann spruce bark beetle and poor timbering practices ' destroyed most of the merchantable timber by the late 1940's. Other agricultural crops are limited by the short growing season (50 to 124 frost-free days, depending on elevation) and limited rainfall (nine inches mean annual precipitation at Rangely) which limits upland dry farming. Temperatures vary widely even at lower elevations and extremes of -421/4C to 3914C have been recorded at Meeker. Water supply in the basin is primarily from snowmelt in the mountainous headwater areas. Presently there are few reservoirs in the basin, and no large mainstem reservoirs exist, so flows in the White River are largely natural except for irrigation depletions and return flows. Since most irrigation water is applied to hay meadows, return flows are lower in dissolved and suspended materials than would be the case if row crops or small grains were irrigated.

111 The White River headwaters originate in primarily igneous schists and granite on the White River Plateau. The geology rapidly changes to calcareous sedimentary rock. Further downstream and in the lower basin, soft marine sedimentary rocks and Pleistocene glacial deposits predominate. Resulting water quality mirrors the change in geology, with calcium carbonate waters of low dissolved solids found in headwater streams to sodium calcium sulfate waters of high dissolved solids at the confluence with the Green River. Because of the easily eroded geology in the lower basin, suspended sediment is high by the time the White River joins the Green River. Native vegetation within the White River basin varies greatly with elevation. Lower elevations with alkaline soils support mat and Gardner saltbrush, shadscale, and several species of grasses and sagebrushes. High elevations are primarily aspen-fir-spruce woodlands with a grass understory or sagebrush grasslands. Intermediate elevations are predominantly big sagebrush grasslands with pinyon-juniper on rocky areas.

Fishes Historical native fish populations in the headwaters and upper White River were primarily Colorado cutthroat trout (Salmo clarki pleuriticus), mottled sculpins (Cottus bairdi) and speckled dace (Rhinichthys osculus). Further downstream, mountain whitefish (Pro- sopium williamsoni), mountain sucker (Catostomus platyrhynchus), bluehead sucker (Catostomus discobolus), flannelmouth sucker (Catostomus latipinnis), and roundtail chub (Gila robusta robusta) enter the fish fauna. Present distribution of native species are similar except for the Colorado cutthroat. Within the White River basin this species is presently restricted to Trapper's Lake where it may have hybridized to some small degree with the introduced Yellowstone cutthroat (Salmo clarki lewisi) and possibly with the rainbow trout (Salmo gairdneri), also an introduced species. Differences between present and past abundances are not known since no historical data is available. Present abundances are relatively high for the native species in the areas suitable to them; and except for the

112 Colorado cutthroat, historical and present distribution and abundances are probably similar. In the lower White River basin flannelmouth sucker, bluehead sucker, roundtail chub, and speckled dace were certainly present in historical times. The historical presence of the Colorado squawfish (Ptychocheilus lucius) in the lower sections of the White River was likely, and bonytail chub (Gila elegans) and humpback chub (Gila cypha) may also have been found in the lower sections of the White River. Prewitt (unpublished data) collected two adult Colorado squawfish from the White River approximately one mile above Piceance Creek in May 1977. This represents the only recent occurrance of any of the threatened or endangered species from the White River. No past or present evidence of spawning by the rare large-river species in known from the White River, through spawning may have or may still occur in the lower reaches. The Colorado cutthroat presently reproduces in the inlet streams to Trapper's Lake. Several non-native species are established in the White River basin. These include Yellowstone cutthroat, rainbow trout, brown trout (Salmo trutta), carp (Cyprinus carpio), red shiner (Notropis lutrensis), fathead minnow (Pimephales promelas), redside shiner (Richardsonius balteatus), creek chub (Semotilus atromaculatus), black bullhead (Ictalurus melas) and channel catfish (Ictalurus punctatus). Mountain whitefish, roundtail chub, fathead minniow, speckled dace, bluehead sucker, and flannelmouth sucker were all common or abundant in 1975 and 1976 (Prewitt, et al. 1976). In this study, sampling was not conducted in the upper portion of the White River basin or in Trapper's Lake, so the trouts were not collected. Cutthroats and rainbow are all common in Trapper's Lake, however, and stream fishing for trout indicates good populations in some headwater streams.

Activities Impacting Fish Mineral resources in the basin include coal, gas, oil, and oil shale. Small amounts of uranium are also present. Most of the known gas and oil in the basin was developed some time ago and present opera-

113 tions are considered primarily laststage recovery attempts and involve gas reinjection and water injection methods. Coal in the basin has not been significantly developed at this time, but future development is likely. Most coal resources are located near Rangely, but substantial deposits are also located north of Meeker in the Danforth Hills, most of which are in the Yampa River basin. The principal undeveloped mineral resource in the basin is oil shale, and the White River basin contains some of the world's largest deposits. Present development of oil shale in the basin is almost at a standstill because of economic unfeasibility and technological problems. However, Ashland and Occidental Oil companies have apparently initiated a joint attempt to develop oil shale deposits in the area. The relatively small tributary dams in the White River basin do not - significantly affect water quality in the mainstem White River. Agricul- tural diversions are numerous on both small tributary streams and the mainstem, but most diversions do not constitute a barrier to fish movement either up or downstream. Because of the vast oil shale reserves, and continuing coal and oil developments, significant changes related to energy development can be expected in the near future in the White River basin. Most of these changes will be to the lower basin, but several water storage and diversion projects are planned for the upper basin. Unfortunately, at this time, water development planning is in preliminary stages, and it is not possible to identify with certainty what will be done and where impacts will occur. A specific example is the Bureau of Reclamation's Yellow Jacket Water Development Project. Seven reservoirs are proposed for this project, and one reservoir is on the White River just upstream of the location at which Prewitt collected Colorado squawfish in June 1977. This dam, if built, would have significant impacts on existing squawfish , populations. However, the status of the Yellow Jacket Project is uncertain primarily because the development of oil shale is, likewise, uncertain. Major impacts of the water projects will be alteration in flows and reduction in discharge at the mouth of the White River. Potential changes associated with coal and oil shale development are primarily the

114 potential for increased sedimentation in the White River and flow reductions caused by alterations in aquifers. The most significant affect of these changes may be additional impacts on the already severely impacted Green River. These changes will occur through reduction of flows which will render the Green River less of a "large river" ecosystem and possibly alter temperature regimes. Present information is insufficient to predict the magnitudes of flow reduction or temperature change that may be expected. In addition, as other developments within the upper Colorado basin render the "large rivers" less suitable for endemic species, these endemic species may be forced into smaller river habitats (if they are suitable) and the lower White River may be an important alternate habitat.

115 UPPER COLORADO RIVER BASIN

General The mainstem Colorado River headwaters in Rocky Mountain National Park in northcentral Colorado, and flows west to the Colorado-Utah state line where it turns southwest. The upper Colorado River basin is generally considered that portion of the basin upstream of Lee's Ferry, Arizona (or Lee Ferry, a different location less than a mile from Lee's Ferry). The upper mainstem Colorado River is approximately 650 miles long, and the basin varies from about 50 miles wide in the headwaters to nearly 200 miles wide in the Glen Canyon area of Utah. Major tributaries are the Eagle, Roaring Fork, and Gunnison Rivers in Colorado, and the Dolores, Green, Dirty Devil, and San Juan Rivers in Utah. The Dolores, Green, and San Juan Rivers are discussed under separate headings. Settlement in the upper mainstem region began with the discovery of gold in 1859 and was related primarily to mining activities until 1880. Water rights date back to before 1880, and by 1885 extensive irrigation works had been established in the Grand Valley near Rifle, Colorado. The first large storage reservoir in the basin, Harvey Gap Reservoir, was constructed in 1891. Most of the present day irrigation works had been constructed prior to 1920. The general topography of the upper mainstem headwaters is highly dissected mountainous plateaus. Streams typically run in deep canyons

Which are often narrow resulting in narrow stream valleys. Highlands ; are typified by rolling ridges and flat-topped mesas. Below Glenwood Springs, Colorado, canyon areas are less frequent and broader valleys are common. Elevations vary from over 14,000 feet in the headwater areas to 3,100 feet at Lee's Ferry. The climate in the upper basin varies widely with altitude. Precipi- tation ranges from over 40 inches annually in the high mountain areas to less than six inches annually in the desert valleys. Wide variations in temperature also occur. The extremes recorded are -51C at Taylor Park,

116 Colorado, to 46C at Lee's Ferry, Arizona. Frost-free periods vary from less than 60 days in the alpine mountain areas to over 190 days at lower elevations. The major land use in the upper colorado River basin is agriculture. Most land is not suitable for cultivation of crops and is used for grazing of sheep and cattle. Timber production is also significant, and forests cover approximately one-third of the land area. In the lower river valleys, extensive irrigated agriculture is practiced. Major crops include hay, small grains, orchard fruits, and truck crops. The headwaters of the mainstem upper Colorado River arise on the igneous and volcanic intrusive rocks which form the backbone of the Rocky Mountains. Mississippian limestones are predominant in the upstream reaches while further downstream sedimentary rocks of the Tertiary or Cretaceous periods are prevalent. The middle reaches of the mainstem are deeply incised into the Green River and Wasatch formations which contain coal and oil shale deposits. The lower parts of the upper mainstem have formed canyons in predominately sand shales from the Jurassic and Triassic periods. The principal water source in the basin is snowmelt, and about one- half of the annual precipitation falls as snow. Summer thundershowers are frequent, but they contribute little to runoff in most instances. Because about 70 percent of the annual flow occurs during snowmelt, base flows in the upper mainstem Colorado River are low. While a large number of small reservoirs have been constructed on tributaries, no large mainstem reservoirs are present on the upper Colorado River below the headwaters except Lake Powell which is only 17 miles upstream of the lower boundary of the upper basin. The vast majority of the available storage capactiy in the upper basin lies with Lake Powell and Flaming Gorge Reservoir (90 percent); less than 1 percent is available on the mainstem above Lake Powell. Because base flows are low, consumptive water use after snowmelt runoff causes serious depletions in the upper Colorado River mainstem. Significant quantities of water are also diverted east of the continental divide and out of the basin, further reducing annual flows.

117 Water quality in the upper mainstem Colorado River is high and averages less than 50 mg/1 total dissolved solids in the headwaters. Because of consumptive uses, natural evaporation, and leaching from marine geologic formations, salinities increase downstream. Salinities average near 500 mg/1 at Grand Junction and Lee's Ferry, Colorado. The major contributors to salinity are irrigation return flows and dissolution of salts in the marine sedimentary rocks of the upper basin. Calcium and bicarbonate are the predominant ionic species in headwater regions, but sodium and sulfate predominate in the middle and lower reaches of the upper basin. Native vegetation in the headwater areas is primarily conifer forest at high elevations and mountain brush/bunchgrass at lower elevations. Middle and lower reaches of the upper basin support a mountain brush or pinyon-juniper community. The lower elevations are characterized by desert shrub or salt desert shrub communities except along streams where a riparian community of cottonwood, willow, and salt cedar is found.

Fishes Historically native fish populations in the headwaters of the Colorado River mainstem were primarily Colorado cutthroat (Salmo clarki pleuriticus), mottled sculpins (Cottus bairdi), Piute sculpins (Cottus beldingi), and speckled dace (Rhinichtyhys osculus). Further downstream in the mainstem were found bluehead sucker (Catostomus discobolus), flannelmouth sucker (Catostomus latipinnis), roundtail chub (Gila robusta robusta), bonytail chub (Gila elegans), humpback chub (Gila cypha), Colorado squawfish (Ptychocheilus lucius), and razorback sucker (Xyrauchen texanus). A considerable number of exotic species have been introduced into the Colorado River upper mainstem. Among the introduced species' which have become common in headwater and cooler upstream reaches are rainbow trout (Salmo gairdneri), brown trout (Salmo trutta), brook trout (Salvelinus fontinalis), Yellowstone cutthroat (Salmo clarki lewisi), and mountain whitefish (Prosopium williamsoni). Even more exotic species have been introduced into warmer water sections of the upper mainstem. Among those that have become common or abundant are fathead minnow (Pimephales promelas), carp (Cyprinus carpio), red shiner (Notropis lutrensis), sand shiner (Notropis stramineus), white sucker (Catostomus commersoni), channel catfish (Ictalurus punctatus), black bullhead (Ictalurus melas), Rio Grand killifish (Fundulus zebrinus), largemouth bass (Micropterus salmoides), and green sunfish (Lepomis cyanellus). Present distribution and abundance of some native species has been considerably reduced (the threatened or endangered species) while other species have undergone little or no change. Within the mainstem and small tributaries, the Colorado cutthroat is known only from one small isolated creek in the Parachute Creek basin. Ironically, this small population of Colorado cutthroat is the best representative of pure Salmo clarki pleuriticus known in Colorado. Within the last five years, another population of Colorado cutthroat in the mainstem headwaters in Rocky Mountain National Park appears to have been extirpated by introduced brook trout. The threatened or endangered large river species have also been reduced in abundance and distribution in the upper mainstem. Where these species once ranged and reproduced as far upstream as Rifle, Colorado, present distribution is limited to the area from Palisades, Colorado, downstream. Reproduction is reported from the upper main stem only from the Walker Wildlife area near Grand Junction for the Colorado squawfish and humpback sucker. Reproduction of the humpback chub is not documented from the main stem Colorado, though it is likely in the Black Rocks area as a small population is reported to be resident in the area. Reproduction by the bonytail chub probably occurs in the Utah portion of the mainstem Colorado as well. For all four species, considerable reductions in abundance are apparent.

Activities Impacting Fish The upper mainstem basin was originally populated by miners, and hard rock minerals are still an important resource. Molybdenum, uranium,

119 vanadium, gold, lead, silver, and zinc are some of the most important minerals, but gypsum, salt, and limestone are also abundant. Oil and natural gas have been produced in quantity, and coal is becoming more important, but oil shale development is presently dormant in the basin. Several minerals such as manganese and bismuth are present but have not been extensively developed. While the potential for water quality degradation is associated with any mining operation, the amount of degradation resulting from currently operating mines in the upper Colorado mainstem basin is generally small. Such was not always the case, and several abandoned mines presently discharge wastes that prevent aquatic life from becoming established in streams below their discharge points. Early placer gold mines (long since abandoned) probably contributed significantly to the reduction in range and abundance of the Colorado cutthroat. Present mine tailings ponds periodically become flooded or washed out, resulting in the release of toxic metal solutions, but control efforts are generally successful. The upper mainstem Colorado River has been the site of extensive recreational development. What began as an effort to promote tourism shortly after World War II developed into extensive winter sports facilities and summer homes for east slope residents. Development was accelerated with completion of the Eisenhower tunnel which improved winter access to the west slope by east slope re3idents. Currently, tourism and both winter and summer sports development is expanding at a rapid rate. With this increased development, the potential for waste disposal and water supply problems is becoming acute. Water rights are presently held in excess of available supply and the cold climate (resulting in extended winter sewage treatment problems) and high quality receiving waters are posing major problems to recreational developers. Present industrial development in the upper mainstem basin is insignificant. No heavy industry, other than mining, currently exists or is likely in the future. What light industry does exist is of the type that has little, if any, effect on water quality or quantity. There are two primary causes for changes in the abundance and distribution of native fishes in the upper mainstem Colorado River.

120 Water use has necessitated construction of water storage in the form of reservoirs. The changes in flow and water quality associated with water use and storage have made large sections of the original range of some of the native species unsuitable. While changes associated with reservoirs are minimal over most of the upper Colorado mainstem, water depletions resulting from consumptive use have been substantial. Man has introduced a number of exotic species into the upper Colorado basin, either intentionally (e.g., the exotic trouts) or inadvertently (e.g., bait "minnow" introductions). Because the large river endemic species had evolved and become specialized for the large river habitat, the reduction in flow coupled with the increased competition from species more adapted to smaller, slower streams, resulted in declines in abundance and restriction of the ranges of the large river endemic species. The introduction of closely related trouts which were tolerant of a wider variety of water conditions and were less subject to angling pressure than the native Colorado cutthroat, resulted in reductions in numbers of the native species through hybridization and selective predation (by man). Other factors may be involved in the reduction of native species (e.g., pollution, climatic change, channelization, etc.) but are judged to be less important than man-caused flow reductions and exotic species introductions. The mainstem upper Colorado River is developing rapidly. Increased demand for energy will almost certainly result in increased coal mining and oil production in the future. Eventually the production of oil from oil shale will be both economically and technologically feasible, and oil shale mining will occur. Recreational development is proceeding at an accelerating rate. All these activities require water, either directly or in support of the increased labor force. Agricultural water demands are also increasing. The result of all these water requirements is that the potential demand on the upper Colorado basin is well in excess of the potential water available. Irregardless of what priorities eventually prevail, it is virtually certain that large changes in the existing flow regime will occur and that these changes will be in the directon of

121 severely reduced flows. The probability of construction of additional storage capacity on the upper main stem is also high. An example of such a project is the proposed West Divide Project of the Bureau of Reclamation. Both reduction in flows associated with increased withdrawals and the changes in flow that occur with reservoir construction will have significant negative impacts on the native fishes, and the mitigation, measures that might be employed are mutually exclusive of the objectives of any water development project. Water development may impact the Colorado cutthroat as well. Construction of high altitude storage projects may act as a barrier to upstream migration of other trouts. This could allow reintroduction of the Colorado cutthroat into areas now occupied by introduced trouts. With proper management and an adequate source of fish, additional pure populations may be initiated. Future development of oil shale will likely impact the last known pure population of Colorado cutthroat in Colorado since this population is located on a tributary of Parachute Creek scheduled to be impacted by oil shale development. This population of fish should be protected and possible used to establish populations in other suitable and protected areas. SAN JUAN RIVER

General The San Juan River basin is located in the Four-Corners area of Arizona, Colorado, New Mexico, and Utah. The basin has an east-west length of about 240 miles and extends nearly 150 miles north-south. Drainage area is about 25,000 square miles and comprises nearly one- fourth of the upper Colorado basin. The river headwaters primarily in Colorado and flows through a small portion of New Mexico before entering Utah and joining the Colorado River in the lower reaches of Lake Powell. A small part of the drainage is located in Arizona. Principal tributaries of the San Juan River are the Navajo, Piedra, Los Pinos, Animas, and La Plata rivers, all of which originate in the San Juan mountains in Colorado. These tributaries provide more than 90 percent of the annual flow in the San Juan River from a little over 20 percent of the drainage area. Early settlement in the area was initiated by gold and silver mining in the 1880's, but ranching activities soon followed. Irrigation for hay and crop production began at about this time also. The majority of the lower elevation lands are on several Indian reservations and this has limited agricultural development to some extent. Climate in the San Juan basin varies from alpine in the mountains to desert below about 6,000 feet elevation. Alpine areas receive more precipitation, have a shorter growing season, and have cooler mean temperatures than the lower elevations. Most precipitation in alpine areas falls as snow between October and April, but at lower elevations most precipitation comes from isolated summer thunderstorms between July and October. Frost-free periods in the basin range from less than 80 days to over 190 days, depending on elevation. Most of the San Juan Basin Lies within the northern Navajo section of the Colorado Plateau physiographic province and is underlain by horizontally layered sedimentary rocks. Erosion has created picturesque mesas, buttes, ridges, and terraces interspersed with broad valleys. Occasional canyons are also present. The downstream portion of the

123 basin is within the Canyon Lands section of the Colorado Plateau physiographic provence, and is typified by level plateaus dissected by deep canyons. While the headwaters of the San Juan River and its major tributaries arise in igneous intrusive and extrusive mountains underlain by sedimentary rocks, most of the basin is formed in various sedimentary formations. Geology in the basin ranges from Precambrian through Quarternary. Soils range from deeper mountain soils through shallow desert soils, and windblown silts and sands are common on the larger mesas. Coal, oil, and gas deposits are common in the basin as are the hard rock minerals uranium, vanadium, lead, zinc, copper, gold, and silver. Deposits of gypsum, halite, and potash are also known but have not been developed. Most surface water in the basin originates as snowmelt in the mountain headwaters; summer thunderstorms usually contribute little surface runoff as most of the rain is absorbed by the porous desert soils. Approximate annual discharge of the San Juan River is two million acre feet (including 0.1 million acre feet diverted from the Dolores River basin). Approximately 100 lakes and reservoirs exist within the basin, but most are very small. Only Navajo, Vallecito, and Lemon reservoirs are of significant size. While substantial quantities of ground water are present in the basin, yields from wells are usually low, and groundwater is higher in dissolved solids (salinity) than surface water. Water quality in the headwater streams of the San Juan basin is generally high, but a few localized areas exhibit toxic heavy metal concentrations from past mining operations. Total dissolved solids are generally under 100 mg/l. Downstream dilution and precipitation of the heavy metals completely mitigate toxic heavy metal concentrations, but salinities increase considerably from water depletions and solutions of salts from the marine sedimentary deposits which comprise the lower basin. Salinities over 1000 mg/1 are common in the lower basin during low flows and during the irrigation season. Because the sedimentary deposits in the lower basin are easily eroded, the suspended sediment load carried by the river is high. The sediment load is further increased by irrigation return flows and by what water does run off the easily eroded dry washes from summer thunderstorms. There is some indication that the sediment load in the San Juan River has recently (until closure of Navajo Dam) decreased from historical levels (period of record since 1904). Native vegetation in the basin varies from relatively barren desert areas to dense forests. Desert and low altitude stream valleys typically support greasewood, shadscale, blackbrush, and other desert shrubs. Higher and less arid areas support sagebrush, bunch grasses, mountain brush and pinyon-juniper forests. High altitude areas in the headwaters are typified by ponderosa pine, Douglas fir, or spruce-fir forests.

Fishes Historically, the native fish fauna of the San Juan basin was comprised of Colorado cutthroat trout (Salmo clarki pleuriticus), mottled sculpin (Cottus bairdi), and speckled dace (Rhinichthys osculus) in the headwater regions. In the warmer headwater sections of the river bluehead sucker (Catostomus discobolus), roundtail chub (Gila robusta robusta), and speckled dace predominated, and in the lower warm water reaches Colorado squawfish (Ptychocheilus lucius), bonytail chub (Gila elegans), flannelmouth sucker (Catostomus latipinnis), and razorback sucker (Xyrauchen texanus) were present. The humpback chub (Gila cypha) probably did not occupy the San Juan River except in the lowermost canyon reaches near the confluence with the Colorado River. Jordan (1891) reported the razorback sucker and Colorado squawfish as far upstream as Durango, Colorado, but the report is based on hearsay evidence. Because these waters were clear and cold during this period, it is unlikely that either species migrated that far upstream. At present, native species in the San Juan basin are much reduced in distribution and abundance. Some species such as the Colorado cutthroat are no longer present. Others such as the Colorado squawfish and razorback sucker are probably extirpated. The roundtail chub, which is still present in most of its previous range in the rest of the upper Colorado River basin and in approximately the same abundance as in historical

125 times, has shown a marked decline in distribution and abundance in the San Juan River. While water depletions and irrigation return flows may have had some effect on this species, the major impact appears to be the construction of Navajo Reservoir. The effects of the cold water discharge of this reservoir extend to below Farmington, New Mexico, or 60 to 70 miles below the dam, but the roundtail chub has become rare throughout the San Juan River below Navajo Dam, an area in which it was once common. Roundtail chubs are relatively common in the upper end of Navajo Reservoir and just upstream. In other similar situations in the upper Colorado River such as below Flaming Gorge Dam, once the effects of cold water discharges are mitigated, the roundtail chub is found at approximately its historical abundance, and appears to be the only Gila species not significantly affected by man's impoundments of the river. It has been suggested (Paul Holden, personal communication) that the reduction in roundtail chub is caused by the lack of a source for recolonization following the fish erradication program just prior to closure of Navajo Dam. This is plausible since the roundtail chub was not common in Lake Powell at the mouth of the San Juan River when Navajo Reservoir was constructed. Another significant cause of the reductions in range and abundance of native species has been the introduction of competitive exotic species. A number of non-native species have been introduced to the San Juan basin including rainbow trout (Salmo gairdneri), brown trout (Salmo trutta), brook trout (Salvelinus fontinalis), kokanee (Onchorhynchus nerka), coho salmon (Oncorhynchus kisutch), threadfin shad (Dorosoma 5 petenense), white sucker (Catostomus commersoni), fathead minnow (Timephal.. promelas), carp (Cyprinus carpio), red shiner (Notropis lutrensis), channel catfish (Ictalurus punctatus), black bullhead (Ictalurus melas), Rio Grande killifish (Fundulus zebrinus), mosquito-fish (Gambusia affinis), bluegill (Lepomis macrochirus), green sunfish (Lepomis cyanellus), smallmouth bass (Micropterus dolomieui), largemouth bass (Micropterus salmoides), white crappie (Pomoxis annularis), black crappie (Pomoxis nigromaculatus), white bass (Morone chrysops), yellow perch (Perca flavescens), walleye (Stizostedion vitreum vitreum), and northern

126 pike (Esox lucius). A number of these species (e.g. the salmons and smallmouth bass) are found only in Navajo Reservoir. Some, however, such as the channel catfish and red shiner are found in abundance in the lower sections of the San Juan River where they would be in direct competition with the razorback sucker or the Colorado squawfish if the latter species are still present in the river.

Activities Impacting Fish Development in the San Juan basin began with gold and silver mining in the 1800's. After the richest gold and silver veins were exhausted, mining became secondary to ranching in the basin's economy. Early mining and ranching activities resulted in considerable aquatic environmental degradation caused by heavy metal pollution and increased sediment loads from tailings and grazing-induced erosion. Improved range management practices and mine reclamation have largely eliminated this problem at present. Following mining and ranching as major economic factors in the San Juan basin, irrigated lands were under cultivation, and irrigation return flows and water depletions are now the major factors affecting the aquatic ecosystem. Dryland farming is also practiced and frequently contributes to an increased sediment load in the river because crop monocultures provide less water retention than undisturbed native vegetation communities. Except for mining there was little industrial activity in the basin until the development of large coal fired electric generation facilities and associated coal mines. Water depletions and associated impoundments represent the major impacts to the aquatic communities brought about by this type of development. Future development in the San Juan basin is expected primarily in the coal mining industry. Power generation associated with coal mining will most certainly increase. Future additional impoundments on the lower San Juan River are unlikely, since the high evaporation rate coupled with the very limited additional water entering from tributarie in the lower reach of the river renders additional impoundments impractical. Substantial development of additional irrigation is dependent on adequate

127 water supplies and on the reduction of the salinity of irrigation return flows. The U. S. Bureau of Reclamation and Soil Conservation Service have proposed salinity control projects in the San Juan Basin, but their realization is in doubt at this time. In any event, additional development in the basin is dependent on additional water supplies. Any additional water supply development will result in at least some further reduction in historical flows in the streams, and in addition, flow regimes will be further altered seasonally (and probably diurnally as well) from historical levels. Any such changes are almost certain to be detrimental to native large-river endemic species, but this fact may be inconsequential if the large-river endemics are already extirpated.

128 DOLORES RIVER BASIN

General The Dolores River basin is located in southwestern Colorado and southeastern Utah. It is approximately 100 miles long and varies from 30 to 70 miles in width. The river begins in the mountains north of Durango, Colorado, and flows southwest to Dolores, Colorado. Here the river turns and flows northwest approximately 100 miles to its confluence with the Colorado River south of Cisco, Utah. The San Miguel River is the only major tributary of the Dolores River. Settlement of the basin began early, and the first recorded irrigation diversion was made in 1844. The oldest reservoir in ,the basin was constructed in 1893. Gold mining established the boom towns of Telluride and Placerville, Colorado, in the San Miguel drainage, but silver, lead, zinc, and copper were also mined. Uranium (carnotite) was mined in the basin as early as 1910. Elevation and climate vary widely within the basin. Some of the headwater streams start at elevations over 14,000 feet while the mouth of the Dolores River is at an elevation of 4,095 feet above mean sea level. Temperatures of 41C to -38C have been recorded, and frost-free periods of 90 to 194 days occur in various parts of the basin. Annual precipitation varies from 7 to 9 inches in the desert valleys to 45 inches in alpine areas. The winter snowpack provides most of the streamflow in the basin. The snowmelt characteristically produces large volumes of water over a several-week period, but does not produce high peak flows. Summer thunderstorms which are typical at lower elevations tend to produce flash floods of high peak flow but do not provide significant volumes of water. The headwaters of the Dolores River begin in igneous mountains, but the majority of the basin is within the eastern part of the Canyon Lands section of the Colorado Plateau physiographic province which is underlain by thick horizontal layers of marine sedimentary rock. Soils in the basin vary from alkaline desert soils to acidic alpine and high mountain

129 forest soils. Both calcareous sandstone-derived soils and fine-textured Mancos shale-derived soils are found in the valleys. Lower elevations typically support a native vegetation of bunchgrass grasslands, aspen, sagebrush, and scattered coniferous timber. Higher elevations are timbered with conifer and aspen-conifer forests. Agriculture is based on livestock production, but cash crops and orchard fruits are also produced. Present day mining is principally for uranium and vanadium. No substantial oil fields occur, but natural gas is produced in San Miguel County, Colorado. A wide range of recreational activities is based on the national forest land and reservoirs. Water quality in the Dolores headwaters is high, but it deteriorates downstream,from the effects of irrigation and other consumptive water uses. In addition, a large anticlinal structure composed of 75 percent salt and gypsum occurs at the junction of the Paradox Valley and the Dolores River. This structure contributes 50 percent of the salinity present at the mouth of the Dolores River. Total non-filterable solids concentrations vary from less than 200 milligrams per liter (mg/1) in the upper basin to over 6,000 mg/1 at the mouth during periods of low flow.

Fishes Historically, the Dolores River probably supported populations of the native "large river" endemic species only in its lowest reaches since virtually all of the river is too small to provide adequate habitat for large river species. Since very early in its history of settlement, the Dolores River has been diverted for agricultural purposes, and today it supports only a depauperate fish fauna in most areas. Trout may be found in the colder headwaters, but the native Colorado cutthroat is unknown from the basin. Native species presently in the basin are roundtail chub (Gila robusta robusta), speckled dace (Rhinichthys osculus) flannelmouth sucker (Catostomus latipinnis), and bluehead sucker (Catostomus discobolus). These native species are common to abundant in the areas of habitat suitable to them (Holden and Stalnaker 1975b). Introduced . fishes found by Holden and Stalnaker (1975b) included carp (Cyprinus

130 carpio), fathead minnow (Pimephales promelas), sand shiner (Notropis stramineus), red shiner (Notropis lutrensis), channel catfish (Ictalurus punctatus), green sunfish (Lepomis cyanellus), and largemouth bass (Micropterus salmoides). All of the introduced species except the largemouth bass were common or abundant in at least one of the seven locations sampled. Holden and Stalnaker (1975b) concluded that the Dolores River was neutral in respect to impacts on the rare native fish species in the upper Colorado basin.

Activities Impacting Fish The U. S. Bureau of Reclamation's Dolores Project will impound all the unappropriated flood flows in the Dolores River and will seriously alter the flow regime of the river. The major man-related depletions at present are irrigation, reservoir evaporation, and export of water out of the basin These depletions account for 14 percent of the total precipitation. So long as the Dolores River does not contribute toxic flows to the Colorado River, it is unlikely that future development in the Dolores River basin will have significant effects on rare fishes. It is unlikely that any conceivable future changes would provide habitat for rare fishes in the Dolores River basin or that the river flows would be raised sufficiently to augment existing flow reductions in the Colorado River. GUNNISON RIVER BASIN

General The Gunnison River basin is located in the west central section of Colorado, encompasses an area of about 8,020 square miles, and drains portions of Gunnison, Montrose, Delta, Mesa, Hinsdale, Saguache, and San Juan counties. The drainage basin is approximately 145 miles long in a east-west direction and 95 miles wide in a north-south direction. The river flows northwesterly from its origin on the west slope of the continental divide to join the Colorado River at Grand Junction, Colorado. Major tributaries of the Gunnison River are the North Fork of the Gunnison, Taylor River, Tomichi Creek, Cebolla Creek, Lake Fork, and the Uncompahgre River. Settlement of the upper basin began about 1873; but settlement of the lower basin began later after a treaty with the Ute Indians. Mining was the major stimulus for early settlement, but agriculture has dominated activities in the basin since about 1893. Climatic conditions in the basin vary considerably because of the wide range in elevations. Some headwaters are at elevations in excess of 14,000 feet while the elevation of the Gunnison River at its mouth is 4,550 feet. Headwater areas may receive more than 40 inches of precipitation annually while the lower valleys receive less than 10 inches. Upper basin lands have an annual frost-free period of less than 70 days while lower basin valleys near Grand Junction average in excess of 190 frost-free days. The geology of the upper basin along the continental divide is predominantly intrusive igneous. In the northern part of the basin, this igneous geology rapidly changes to marine sedimentary formations including the Mancos shale formation. Abundant coal deposits exist in this area and have been mined by underground methods since the turn of the century. The '.gneous geology persists further down the basin in the south part of the basin, but eventually gives way to marine sedimentary . rocks. Soils range from those typical of high mountain woodlands to alkaline desert types and generally tend toward desert soils in a downstream progression. 132 The water supply in the Gunnison basin is derived principally from snowmelt on the Anthracite, West Elk, and San Juan mountains. Watershed yields within the basin vary from less than one inch to over 30 inches annually. Peak streamflows in areas not influenced by the Currecanti Project dams generally occur in late spring or early summer. A number of reservoirs have been constructed, primarily to supply irrigation water, but only those of the Currecanti Project on the mainstem Gunnison River above the Black Canyon of the Gunnison, have a major effect on stream flows in the river. The dominant use of water in the basin is for irrigation with about twice as much water depletion occurring from this use as from all other uses combined. Water quality at high elevations in the basin is generally excellent with low dissolved solids content. The effects of irrigation depletions and leaching of marine-derived soils becomes progressively greater downstream, and by the time the Gunnison River reaches the Colorado River, it is turbid, high in dissolved solids, and relatively warm. The dominant native vegetation ranges from alpine mountain forest to desert shrubs. A large portion of the basin is used for irrigated crop production ranging from hay to orchard fruits. Most of the land which is unirrigated is used for grazing of sheep and cattle. National forests within the basin support a moderate timber industry.

Fishes Native fishes historically found in the Gunnison River included all six threatened or endangered species except the Kendall Warm Springs dace and humpback chub. The bonytail chub (Gila elegans), Colorado squawfish (Ptychocheilus lucius), and razorback sucker (Xyrauchen texanus) were common in both the Gunnison and Uncompahgre rivers at least as far upstream as Delta, Colorado (Evermann and Rutter 1895). Coldwater streams in the upper basin supported the Colorado cutthroat trout, but stocking of non-native trouts soon eliminated this species.

133 Other native species found in the basin included roundtail chub (Gila robusta robusta), speckled dace (Rhinichthys osculus), bluehead sucker (Catostomus discobolus), flannelmouth sucker (Catostomus latipinnis), mottled sculpin (Cottus bairdi), and Paiute sculpin (Cottus beldingi). All of these species except the Paiute sculpin were easily collected and were apparently abundant in appropriate habitats. Present distribution of the rare species in the basin may be limited to the squawfish and possibly the razorback sucker. While these species may have ranged somewhat further upstream than Delta, Colorado, in the Gunnison and Uncompahgre rivers, it is unlikely that they presently range above Delta if they are present at all. Abundances have been greatly reduced and bonytail chub, squawfish and razorback sucker have not been collected in the Gunnison River above Grand Junction in recent years. A number of exotic species have been introduced into the Gunnison River basin. These include Yellowstone cutthroat trout (Salmo clarki lewisi), rainbow trout (Salmo gairdneri), brown trout (Salmo trutta), brook trout (Salvelinus fontinalis), lake trout (Salvelinus namaycush), kokanee (Oncorhynchus nerka), northern pike (Esox lucius), fathead minnow (Pimephales promelas), carp (Cyprinus carpio), red shiner (Notropis lutrensis), and sand shiner (Notropis stramineus), white sucker (Catostomus commersoni), longnose sucker (Catostomus catostomus), channel catfish (Ictalurus punctatus), black bullhead (Ictalurus melas), Rio Grande killifish (Fundulus zebrinus), largemouth bass (Micropterus salmoides) and green sunfish (Lepomis cyanellus). Several of the exotic species have become abundant. Of these the fathead minnow, carp, red shiner, sand shiner, and green sunfish may have deleterious effects on the native species because of their abundance and competitive habits. While no populations of pure Colorado cutthroat are known in the basin, if any do remain, they are in potential danger because of the possibility of hybridization with the abundant rainbow trout. Activities Impacting Fishes Major development is occurring in the Gunnison River basin at the present time. Most of this development is related to coal mining, but additional agricultural water development is also proposed. Because the Gunnison River basin native fishes are already heavily impacted by past water developments and exotic fish introductions, the overall impacts from proposed new water developments (such as the Fruitland Mesa project) on native fishes will be less significant than they would be in a basin with little water development such as the Yampa River basin. A major portion of the coal development presently occurring or proposed is by underground mines. With the exception of mine drainage and coal processing activities such as screening and washing, underground mines create less land disturbance and have a smaller impact on the aquatic ecosystems than do surface mines. Because most of the coal being developed in the Gunnison River basin is low in sulfur, acid mine drainage is unlikely to cause significant aquatic impacts. Residue from screening and washing activities and runoff from waste piles are presently well regulated by both state and federal agencies and are unlikely to have a significant impact on basin aquatic systems. The major'impact of any of the proposed mineral resource developments in the basin is likely to be water depletions. The waters of the basin are already depleted to a major extent by agricultural development downstream of the majority of the mineral development. Major downstream impacts of the mineral development will fall then on agricultural uses. Little if any of this impact will carry through to the aquatic ecosystem to add additional impact above that resulting from the agricultural impacts. A possible impact from mineral extraction activities may occur in the headwater streams through water depletion. If such depletions were to occur on streams supporting the Colorado cutthroat trout, the impact on this species could be significant. While no populations of Colorado cutthroat trout are known in the Gunnison basin, all areas with a potentia for harboring a remnant population of this species have not been surveyed. Thus any development in the basin which would impact headwater streams should be preceeded by thorough surveys of the headwater streams to establish the presence or absence of the Colorado cutthroat trout. 135 The lower portions of the Gunnison and Uncompahgre rivers, which once supported reproducing populations of Colorado squawfish, razorback suckers, and bonytail chubs, do not appear to support the reproduction of these species now. Once the range of habitats suitable for reproduction of these species is defined, it may be possible to restructure the water regime in the lower Gunnison River basin to again support the rare large-river endemic species. V. MAJOR FACTORS INDUCING ENVIRONMENTAL CHANGE

It is difficult to document conclusively the changes that have taken place in the upper Colorado River system or their causative factors. The problem lies primarily with the lack of quantitative documentation concerning historical environmental conditions. Although a problem, this data gap should not represent an insurmountable obstacle. Data, professional expertise, and scientific judgment are important and valid parts of professional documents and are essential to this section. The physical character of the upper Colorado River system has changed considerably over the past 100 years bringing about parallel changes in the flora and fauna. Agriculturally induced changes such as channelization and rip-raping to prevent stream bank cutting, irrigation withdrawals and return flows, fertilization, cultivation, and grazing represent gradual but accumulative impacts to the aquatic ecosystem dispersed in time and place. Dams, large quantity water withdrawals, major channel changes, and point source pollution represent abrupt impacts. Abrupt changes are obvious and less difficult to quantify; however, both gradual and sudden habitat modifications have favored establishment of non-native fish in most of the upper basin, have induced population alterations, and may lead to the elimination of sensitive species. Gradual changes generally effect a large area and are sometimes not identified until the effect is severe, and because of their less obvious nature may seem to be less important than a sudden obvious change which affects only a small area in a minor way. This section will attempt to identify significant gradual and sudden changes, the factors responsible, and their significance.

Livestock Grazing Livestock grazing takes place on about 84 percent of the land of the upper basin. An estimated 850,000 cattle and 1.3 million sheep grazed the upper basin during 1965. Two distinct grazing seasons are recognized. In the summer, the herds of cattle and sheep are grazed in the high mountain valleys,

137 usually on public land where grass and water are abundant and the temperature is cool. In the winter, the herds are taken from this upper zone to the more moderate climate of the intermediate zone, usually onto private lands. The result of this practice is that extensive grazing activities are distributed throughout the upper basin, although use of the land is seasonal. The increase in sediment in the river and accelerated bank erOsion in the early 1900's is likely correlated with the increase in grazing in the upper basin (Upper Colorado Region State-Federal Inter-Agency Group 1971). Livestock grazing can be characterized as a gradual, cumulative impact, rather than as a sudden or catostrophic impact. Western lands have been grazed for more than 100 years, and many degraded areas may appear natural, even to local residents. Heavy livestock grazing results in the eventual loss of riparian vegetation through excessive use. This in turn leads to destabilized stream banks and greatly altered stream channels. The stream morphology can be changed from a natural, clean-cut meandering stream with rock or gravel bottom, to down-cut entrenched, or spreading, braided streams with silted substrate and poorly defined banks. This alteration in channel morphology converts an optimum trout habitat (stable undercut banks, deep water, rock or gravel substrate) to a very poor one (no undercut banks, shallow, high flow fluctuation), favoring replacement of trout by minnows and suckers or small non-native fishes. The direct impact is on the physical habitat, but the indirect impact of warmer, silt laden waters may extend far downstream. The concentration of livestock along streams and rivers renders the banks unstable, usually destroys their soil-holding capacity, and acceler- ates local erosion. Animal activity on the banks breaks up the integrity of the root-soil matrix, and grazing reduces the stands of vegetation necessary for moisture and soil retention. Grazed areas are capable of recovery if fenced exclosures are constructed. The effects of grazing have been well documented and a symposium was held in Sparks, Nevada, on May 3-5, 1977, on the impacts associated

138 with grazing in the west. It was revealed at this symposium that trout biomass is 3-4 times greater in protected areas than in overgrazed areas within the same stream (Duff, Marcuson, Clair, and Storch 1977). Lorz (1974) found that a section of the Little Deshutes River, Oregon, that had good riparian vegetation and stable stream banks had a standing crop (biomass) of 175 lb/acre of trout; whereas only 48 lb/acre occured in a section where livestock impact had destroyed the riparian vegetation and destablized the stream banks. Hunt (1969, 1976) demonstrated by experimental alteration of sections of Lawrence Creek, Wisconsin, that shallow, high velocity flows without suitable cover produce considerably less trout biomass, and that this result was due to differences in physical habitat and not food supply. The relationship of suitable habitat and natural channel morphology to trout abundance was discussed by Mullan (1975) in regard to the Duchesne drainage, Utah, of the upper Colorado River basin. White (1973) and Wesche (1972, 1974) also document that undercut banks, adequate cover, and proper stream morphology are necessary for normal trout production. Ten years of study have shown that ungrazed water sheds averaged 45 percent less sediment runoff than grazed watersheds in the upper Colorado River basin (Lusby 1970, Lusby et al. 1971). Chapman (1933) described tremendous sediment loads and erosion problems due to overgrazing during the "open range" period. Livestock grazing is compatible with trout production if range managers are cognizant of reasonable livestock densities and vulnerable stream segments. In meadow areas where dense stands of willows may completely encase small headwater streams, moderate grazing pressure may be beneficial by opening sections of the stream to sunlight and by allowing angler access (Behnke, 1977). Likewise compatible grazing could occur at high elevations with reasonable livestock densities. The grazing season is short and the riparian vegetation of conifers and large woody plants provides dense, deep root systems which stabilize the banks well. Severe damage typically occurs in arid and semi-arid foothill regions where livestock concentrate along stream bottom lands, because by mid-summer such areas hold the only water and green vegetation.

139 Cattle excrement reaching the river generally does not represent a significant impact on fishes in a drainage, but if cattle density is extremely high and the stream is intermittent, the water quality changes could have a severe negative impact. In typical headwaters organic enrichment by cattle would most likely increase primary and fish productivity. Other major impacts of livestock on native fishes include: loss of spawning gravel and reduced feeding efficiency due to increased sediment load and siltation; higher water temperatures due to loss of shading vegetation; and loss of water retention in the watershed due to vegetation removal. This last impact may alter flow regimes resulting in increased peak flows and decreased minimum flows. Streams in denuded watersheds have boom-bust cycles and may dry up completely by late summer where formerly permanent flows and fish populations were present.

Parasites and Diseases Parasites and disease probably do not pose a serious threat to the fishes of the upper Colorado River basin, with the possible exception of the cestode Proteocephalus in Colorado squawfish. Sporadic occurrences will be found in any system, however, in natural populations, mass infestations or deaths are uncommon. Dotson (1960) noted open sores on flannelmouth and bluehead suckers. This condition was probably associated with pollution emanating from the city of Green River, Wyoming, for the incidence of occurrence increased in the vicinity of the city. Vanicek (1967) noted that tapeworms were a common infestation in squawfish and up to 80 percent of the intestines analyzed were infected. The tapeworm in question, Proteocephalus ambloplias, has its intermediate stage in forage fish, and completes development in predator fish consuming infected prey. This tapeworm may be a serious threat to Colorado squawfis because it is probably not native to the Colorado River basin. Therefore the Colorado squawfish would not have had time to evolutionarily adjust to infestation by physiological adaptations characteristic of parasite host relationships of long evolutionary standing. If this is the case,

140 then Proteocephalus places Colorado squawfish at a competitive disadvantage to non-native predators such as channel catfish and largemouth bass which have always coexisted with this tapeworm. The evidence that Proteocephalus is not native to the Colorado basin is circumstantial, but convincing. This parasite has a completely aquatic life cycle (predator fish is the final host) and would be expected to transfer from one drainage basin to another only by movement of fishes. The high degree of endemism of Colorado basin fishes would suggest the same endemism for parasites restricted to water for their entire life cycle. Bangham (1951) did not find this parasite in the upper Snake River or Yellowstone River which are contiguous drainages to the upper Green River. Thus, it is likely that Proteocephalus was introduced into the Colorado River basin with introduced fishes. Reduced size of captured (last 20-30 years) Colorado squawfish in comparison with historical size also supports evidence that Proteocephalus may have negative impact. Leeches were reported attached to most fishes of the upper Green River (Dotson 1960). Hagen and Banks (1963) and Vanicek (1967) found an external parasite, the copepod Lernaea sp., on Colorado squawfish and roundtail and bonytail chubs. Heavy infestations of this copepod were found on squawfish and razorback suckers caught in large, man-made backwaters near Grand Junction, Colorado (Seethaler, Holden personal communication). This warm, eutrophic area apparently provides ideal conditions for this parasite, and Colorado squawfish collected from this area were found to be in relative poor condition (Toney 1974).

Dams Dams and their associated reservoirs are one of the major factors causing change in the upper Colorado River basin ecosystem. The impoundments and downstream tailwaters have virtually eliminated all native species from these environments and represent a key factor in the future of the basin fishery. The effects of impoundments are largely twofold: 1) replacement of lotic ecosystems by large lentic environments, and 2) significantly

141 altered water quality in tailwaters and reaches downstream from the dam. A third impact applicable only in two cases involves pre-impoundment fish eradication programs (Navajo Dam and Flaming Gorge Dam). The change from a lotic to a lentic environment appears to be the major factor causing shifts in species composition. The four rare fishes of the lower and intermediate zone have evolved characteristics suitable for life in turbid lotic environments and lack lacustrine adaptations. The clear, deep lentic character of reservoirs is not favorable for sustaining populations of these fish especially when in competition with non-native, lacustrine-adapted fishes. Most species originally inhabiting a river are found in the reservoir soon after dam closure but disappear within a few years. This suggests that fish populations of flooded river sections remain in the reservoir for a time and either move slowly upstream or remain in the reservoir. Those individuals that remain in the reservoir fail to reporduce and ultimately die of old age. Bonytail chubs and razorback suckers have been observed spawning in several reservoirs, however, no juveniles have been found (Douglas 1952, Utah Division of Wildlfie Resource 1968). The razorback sucker may be the exception for indications of recruitment have recently appeared in lower Colorado River reservoirs (Kobetic, personal communication, Holden 1976). The major problem concerning bonytail chub, humpback chub, and Colorado squawfish within reservoirs appears to be the loss of adequate habitat necessary for maintaining self-sustaining populations. In situations where these native fishes are locked in (chain of repeating reservoirs such as in the lower Colorado River), the populations consist of old, large fish; when as avenue of escape is open, such as in Lake Powell, these species disappear from the reservoir rather quickly. It is reasonable to conclude that the four mainstream rare fishes are not adapted to large, lacustrine environments. The decrease in native fish populations below Flaming Gorge Dam immediately after closure has been documented (Vanicek, Kramer, and Franklin 1970). They concluded that reduced water temperature was the

142 main factor precluding reproduction from the dam to the mouth of the Yampa River, a distance of 65 miles. Holden and Stalnaker (1975a) found that the same situation occurred in the area below Glen Canyon Dam comprising all of Marble Canyon and most of Grand Canyon. Other studies have come to the same conclusion (Minckley and Deacon 1968, Wiltzius 1976, Mullan et al. 1976). Holden and Stalnaker (1975a) noted the loss of reproduction by Colorado squawfish and bonytail chubs in the Green River of Dinosaur National Monument during their 1969-1971 studies. Earlier studies by Vanicek, Kramer, and Franklin (1970) demonstrated that abundant reproduction occurred there from 1964 through 1966. After closure of Flaming Gorge Reservoir, a trout fishery was established in the tailwaters. As the water level in the reservoir increased in 1966, the hypolimnion rose closer to the discharge level and the tailwaters became colder. The Utah Division of Wildife Resources noted that the reduced temperatures altered the trout fishery below the dam by reducing growth rates. The colder discharge from Flaming Gorge has had a significant effect on downstream temperatures. Prior to 1966 Holden (1973) indicated that the Green River was sufficiently warm above the mouth of the Yampa River in Dinosaur National Monument for Colorado squawfish reproduction. After 1966, temperatures in the Green River were too low for Colorado squawfish reproduction until the river had mixed with the warmer Yampa River (Holden 1973, Vanicek 1967). Since 1976 no indication of Colorado squawfish reproduction has been noted in the Green River in Dinosaur National Monument (Seethaler, McAda, and Wydoski 1976) although young squawfish have been collected below the monument. Large numbers of sexually ripe Colorado squawfish have been noted in the lower Yampa River (Holden and Stalnaker 1975a, 1976b), and it is probable that this represented a spawning migration. It appears probable that these fish are being diverted from upstream migration in the Green River by the more suitable temperatures in the Yampa River, since Vanicek, Kramer, and Franklin (1970) did not find the same movement into the Yampa River during their studies. Successful

143 spawning has not been noted in the Yampa River, at least in collections since 1969, although fish collected in the lower section of the river were successfully spawned at Willow Beach National Fish Hatchery in 1973 (Toney 1974). In addition, recent collections by the Colorado River Fishes Recovery Team has recently found young squawfish only below Jensen, Utah. This indicates that the effect of the cold water discharge from Flaming Gorge Dam may extend further downstream than Dinosaur National Monument, and that the Yampa River may not offset the cold water discharge as much as it did in the 1966 to 1969 period. While the distribution data is meager, it appears that 1966 to 1969 may have been the end of successful squawfish reproduction in the Green River above Jensen, Utah, and the recent movement of squawfish into the Yampa River may be an attempt to escape the colder waters of the Green River. With the completion of penstock modifications on Flaming Gorge Dam, warmer water will be released, and a possibility exists that native fishes will become reestablished in the Green River above the mouth of the Yampa River. This discussion of temperature alteration by large dam construction provides a relatively well documented example of one impact that dams with deep-water withdrawal have on warm water fisheries. Additional physical alterations that occur below dams include altered daily and seasonal flows. These altered flows may upset fish movements by causing maximum discharge to occur at different seasons than in an unaltered stream. They may also result in altered sediment transport capacity for great distances downstream. This change is usually in the form of increased sediment transport capacity at reduced flows caused by deposition of the original bed load in the reservoir, and may result in increased channel entrenchment.

Introduced Fish Species Exotic fishes may have negative impacts on native fish in four ways: first, through competition for food and space; second, as predators on eggs, larvae, and young fish (Miller 1961; Minckley and Deacon 1968; Holden and Stalnaker 1975a; Seethaler, McAda, and Wydoski 1976); third,

144 through hybridization and loss of pure gene pools; and fourth, through introduction of disease and parasites. The major supportive data for these hypotheses is the correlation between the decrease of native species and the increase of exotic species and hybrids. Introduced species that may be considered potential threats to native fish in the upper basin are channel catfish, carp, white sucker, longnose sucker, red shiner, sand shiner, redside shiner, green sunfish, and rainbow, brown, brook, and non-native cutthroat trout. Other species may pose a potential threat in restricted areas but they are not of serious concern throughout the basin. The white sucker is often a dominant fish in major tributaries such as the upper Yampa. Its niche is probably somewhat intermediate between the bluehead and the flannelmouth and it hybridizes with both (Prewitt 1976). The longnose sucker is sporadic in distribution but is now a dominant species in the upper Gunnison River below Taylor Reservoir and below Blue Mesa in Black Canyon (Wiltzius 1976). This tailwater environment is a niche to which the longnose is better suited than any native species. Carp and razorback suckers are found in similar habitats and use similar food sources. Carp flourish in warm, still backwater areas which are probably essential for early stages of razorbacks, while the adult razorbacks utilize the river proper more than carp. Both species are bottom feeders and utilize plant debris and associated invertebrates. While abundant quantities of plant debris are common in most sections of the Colorado River basin, aquatic invertebrates are often scarce. However, the wide range of foods utilized by both species suggests that competition for food is not likely to be a major problem except in localized situations. Carp were introduced into the basin near the turn of the century. The populations have not become extensive in most areas of the upper basin except near large man-made backwaters. This suggests that unmodified conditions in the basin are not well suited to carp and that if future channel alterations are limited, carp are not likely to become overabundant as they have in eastern waters. Channel catfish are omnivorous and use much the same food sources as Colorado squawfish and bonytail and humpback chubs. However, channel

145 catfish are often less piscivorous than either Colorado squawfish or roundtail chubs and thus may not be significant competitors with these two native species. Channel catfish were introduced into the Colorado River basin quite early and had become well established prior to the sharp declines noted in squawfish populations in the 1960's. This fact indicates that competition between the channel catfish and squawfish is not entirely responsible for squawfish declines, but the presence of large channel catfish populations may be a contributing factor in the long-term declines noted since the 1930's. Another potential impact of the introduction of exotic fishes occurs when small forage species (e.g. red shiner, sand shiner, and redside shiner) become established in areas such as the Colorado River basin. The adults of these small fishes feed on the same foods as juvenile native species. In addition, the larvae and juveniles of these exotic fishes feed on the same foods and in the same areas as larval native species. Of the non-native species found in the Colorado River basin, the red shiner especially is noted for feeding on smaller fishes, and this species may be predacious on native larvae and juveniles. Thus the exotic minnow introductions may result in a high degree of predation and competition with larval and juvenile forms of the native species. The red shiner was well established in the Green River in the areas where Vanicek (1967) found good reproduction of squawfish and bonytail chubs. Holden (in press) indicated that the competitive advantage of the red shiner over juvenile native species decreased where pools and riffles dominated in the Escalante River of Utah. Man-caused changes in the Colorado River may have also shifted the competitive advantage to red shiners. Predation on young native fishes by exotic species certainly takes place, but probably does not always represent a significant factor. When non-native or introduced species "ruin" a fishery, it usually is not from predation but from competition for a common food supply. Redside shiners, creek chubs, Utah chubs, and golden shiners (all forage fish) can virtually destroy a trout fishery because they monopolize the food supply.

146 Redside shiners were first found in the upper Green River in 1938 and became the dominant species by 1959-1960. This increase in the redside shiner population paralleled a decrease in abundance of Colorado squawfish to the point that in 1959-1960 squawfish were rare and no young were found. Redside shiners were first found in the Yampa River in 1961; they were moderately abundant in 1964-1966 and were dominant in 1975-1976. No squawfish reproduction has been noted since 1969. The negative interaction of introduced species will almost always be the result of food competition or environmental modification (such as carp "rooting" which increases turbidity and disrupts habitats) rather than predation. The influence and impact that exotic species exert on native population generally increase significantly when native populations are already reduced by other factors such as habitat alteration. The competitive advantage generally favors the exotics in conditiion of habitat alteration, Another influence on squawfish status is that historically, squawfish ate native fishes (probably Gila elegans, because of its main channel association). Now they must eat non-native fishes for the bulk of their diet. The non-native cyprinids are much smaller than bonytails, and none are abundant in the large, open areas of main channels. Thus, the bonytails are essentially gone and no substitute forage have taken their place. In competition for non-native forage species, the squawfish is probably at a disadvantage when compared to non-native predators.

Hybridization Hybridization in fishes may result from a number of factors. The introduction of closely related species provides opportunity for hybridization that was not available prior to their introduction. Exotics 01 hybridize and severely reduce the native population's pure geneLP0 , a relatively short period of time as has occurred with the natiie trout. 0 Shifts in population structure may induce hybridizati n.

populations are reduced, individual fish may find it diffica a conspecific mate. In searching they may extend their a

147 into adjacent populations of the same or different species and mate with them. As species abundance is reduced to a very low level, the chance of finding a conspecific mate is severely reduced and frequency of mating with a closely related species is increased. Environmental alteration (including introduction of non-native species) is believed to be one of the major factors bringing about hybridization in upper Colorado River fishes. It is well documented (particularly for cyprinid fishes) that man-induced environmental dis- ruptions which tend to breakdown or obscure specific niches and stimulate hybridization between two species which formerly maintained reproductive isolation (Gilbert 1961, Hubbs 1955, Hubbs and Strawn 1956; for a general discussion on isolating mechanisms in fishes see Hubbs 1961). Because the factors maintaining reproductive isolation have been removed or ob- scured and hybridization occurs, the validity of species recognition does not change. For an indepth treatment refer to the discussion on speciation introducing the section on species description (Section III). Verified and suspected hybrids of roundtail, bonytail, and humpback chubs, and between flannelmouth and razorback suckers have been collected in the upper basin. In the case of the chubs, Holden and Stalnaker (1970) found that of 309 Gila specimens studied only three were grouped as robusta x elegans hybrids. These results indicate that this cross does not appear to have occurred to any significant extent. Suspected hybrids between elegans and cypha appear more common. The morphological characteristics do not place them directly between the suspected parents but form a stepped series bridging the morphological gap (Holden and Stalnaker 1970). However many values appear outside the range of either elegans or cypha. This indicates that introgression and back-crossing may have occurred and that probably gene flow from robusta was also present in Holden's older specimens. These intergrades have been reported from the upper Green River (Bosley 1960, Smith 1960), the middle Green River (Holden and Stalnaker 1975a) the lower Yampa River (Holden and Stalnaker 1975b, Seethaler, McAda, and Wydoski 1976), and Lake Powell (Holden and Stalnaker 1975, Hinckley 1973). Specimens from the Colorado River near the Utah-Colorado border (Kidd 1977) appear to be hybrids between cypha and robusta as do specimens from the upper Green River and the Yampa River (Holden, personal communication). This suggests that in the area where robusta is the dominant population cypha x robusta hybrids are common; whereas in areas where elegans predominates, elegans x cypha crosses will be found. Because elegans is so rare now, only robusta is left to hybridize. Humpback chub hybrids were known from areas such as the upper Green River prior to completion of Flaming Gorge Dam (Holden, personal communication) and Kobetich and Holden (1976) suggest that cypha populations have been decreasing over a long period of time. This would suggest then that hybridization and population changes were caused by natural circumstances and not necessarily by man. This could be true, but man- induced changes did not start with the construction of Lake Powell or Flaming Gorge Reservoir, but began when man first grazed his cattle, rip-rapped the banks, or withdrew water. Destruction of the barriers maintaining reproductive isolation could have began at that time, and the rate of destruction could have only relatively recently increased due to major developments in the basin. Hybrids between razorback and flannelmouth suckers have been collected since 1889 and were taken in several upper basin locations before 1950 (Hubbs and Miller 1953). Vanicek, Kramer, and Franklin (1970) collected 73 razorbacks and 16 hybrids (18 percent) from the upper Green River, Holden and Stalnaker (1975a) found 53 razorback suckers and 40 hybrids (43 percent) in their studies, and Seethaler, McAda, and Wydoski (1976) caught 8 hybrids (14 percent) and well over 50 razorback suckers. Kidd (1977) captured 234 razorback suckers in the Colorado River, but reported no hybrids (absence or hybrids in this study is unlikely--it is believed that the researcher was unable to identify hybrids). It is not certain from these data that hybrids are increasing in abundance as suggested by Seethaler, McAda, and Wydoski (1976), but there is no baseline data from which to base comparisons, and recent data is not sufficient to make a judgment either way. McAda and Seethaler (1975) note that razorbacks and flannelmouth suckers spawned at the same time and in the same sites in the Yampa River. The spawning behavior of razorback suckers was observed by Douglas (1952) and Jones and Summer (1954). They noted that one female was surrounded by several males and believed that this behavior would tend to guard against hybridization unless flannelmouth suckers had a similar behavior and mates were readily swapped. Spawning in groups generally guards against interspecific mixing. The question remains whether spawning sites were historically shared or whether recent changes within the river have caused this phenomenon. The occurrence of hybrids in early razorback sucker populations suggests site sharing, at least in some areas, occurred naturally. Recent habitat modification may have increased this sharing, especially in certain areas, and thus increased the rate of hybridization. When the razorback sucker population was larger, the rate of hybridization probably did not present a threat. At present, with the population severely reduced, the rate of hybridization may be a serious factor. If the hybrids are fertile the impact will be much greater. Kidd (1977) mentions that razorback suckers hybridize with bluehead, white, and longnose suckers, however, he presented no supportive data. Gustafson (1975) noted hybrids between razorback suckers and the Utah sucker (Catostomus ardens) from Lake Mohave. The coastal cutthroat trout, Salmo clarki clarki, is sympatric with the rainbow trout from California to Alaska, where the two species maintain reproductive isolation as a result of niche separation. This sympatric distribution of naturally occurring cutthroat and rainbow trouts with reproductive isolation is the basis for recognition of separate species for rainbow and cutthroat trout. When rainbow trout have been introduced by man into interior waters and where the only native trout are various subspecies of cutthroat trout, hybridization has been the invariable result. The hybrids are fertile and this generally leads to hybrid swarms with the rainbow trout genotype typically becoming dominant in warmer, lower elevation waters. Often the persistence of a predominant native cutthroat trout genotype occurs in smaller, colder, higher elevation headwater streams (Behnke and Zarn 1976).

150 Besides the problem of rainbow trout hybridization, the purity of interior subspecies of cutthroat trout has been affected by the historical practice of fish culturalists to lump all cutthroat trout as "native" trout. This led to the widespread introduction of Yellowstone cutthroat trout (Salmo clarki lewisi) into the Colorado River basin, and subsequent hybridization. Other subspecies of cutthroat trout have been stocked into the upper Colorado River basin and hybridize with the Colorado cutthroat trout (S. c. pleuriticus). The greenback cutthroat trout (S. c. stomias), was propagated from Twin Lakes in the 1890's and early 1900's in Colorado. Utah continues to stock a hybrid between rainbow trout and Yellowstone cutthroat trout from Strawberry Reservoir as "native" trout. Wyoming stocks cutthroat trout native to the upper Snake River (fine spotted Snake River cutthroat, an undescribed subspecies) in the basin. The consequence of introductions of rainbow trout, non-native subspecies of cutthroat trout, and various hybrid combinations during the last 100 years into the upper Colorado River basin, has been the virtual disappearance of pure populations of S. c. pleuriticus. Pure populations only exist in waters completely isolated from contamination by non-native rainbow and cutthroat trouts (Behnke 1974, 1975, 1976a, 1977; Behnke and Zarn 1976).

Industrial and Municipal Pollution Industrial utilization of the upper basin is light and large population centers other than Grand Junction, Colorado, do not exist. Pollution from industrial or municipal locations is usually a point source discharge having a very site specific effect. Reduced or altered fish populations may be found in those specific areas, but probably pollution has not contributed significantly to the overall declines of the rare fishes. On the other hand, the reduced population status of the rare fishes increases the need for looking in detail at where development is taking . place and how it can be done and be made compatible with the environment. Sewage from Green River, Wyoming, and oil wastes from the Union Pacific Railroad yards had a major impact on the Green River which

151 4 extended far downstream. The Colorado squawfish and even the channel catfish were rare by 1960 (Bosely 1960). Investigators collecting numerous humpback chub and squawfish at Hideout Flats on the Green River near Flaming Gorge Damsite in 1950 would be covered with oil on entering the water. Other investigators have noted site specific alterations of fish population near the town of Green River, Wyoming (McDonald and Dotson 1960, Woodbury 1960) and Grand Junction, Colorado (Holden and Stalnaker 1975a). Mining activities played a major role in the history and development of the upper Colorado River basin. The coal reserves, vast oil shale reserves (one of the largest in the world), uranium deposits, and other mineral reserves dictate that present mining activities will increase, and major new development will soon be taking place. Mining can have a wide range of environmental impacts. The magnitude depends upon the mineral mined, the scale of mining, mining and processing methods, transportation methods, and other vairables associated with any development such as population increase, road and railroad construction, water use, and the usual socioeconomic impacts. Nolting (1956) demonstrated the detrimental effects of uranium mill waste disposal on the fish populations of the lower San Miguel and Dolores Rivers in southwestern Colorado. He observed that progressive increases in ore processing resulted in progressively more harmful effects on fish populations downstream. Depletion of fish stocks paralleled the uranium production years. Fish life was totally eliminated and productivity greatly reduced in large sections of the streams. The overall impact that mining activities are having on the upper Colorado River is difficult to determine quantitatively for the number of studies are limited. The potential future development indicates that the threat of industrial pollution should be very carefully evaluated.

Logging Logging operations generally result in an increase in the temperature and turbidity of associated streams. Almost all timber cutting occurs in the upper zone where natural waters are clear and cold. Clear cutting

152 activities open large, steep areas to erosion and usually result in high sediment loads in nearby streams. The suspended solids and resultant sediment deposition represent a major impact to the stream. Large areas critical to spawning activities may be silted in completely over a very short period of time. The temperature regime of any stream is a key factor in determining the quality of habitat, for temperature is a principal regulator of biological activity in the aquatic environment. Water temperature influences oxygen availability to fish and can be a critical factor, especially in the early stages of fish development. As water warms it becomes more conducive to the growth of bacteria, some of which are pathogenic to fish. A small temperature rise in the Columbia river allowed Columnaris, a pathogenic organism, to attain epidemic proportions and nearly eliminated a population of sockeye salmon (Brett 1956). Temperature greatly influences the composition of an aquatic community by influencing the species which can survive and determining which species will predominate. Green (1950) studied the effect of clear cutting on trout streams and noted that the maximum weekly recorded temperatures during May were 13C higher than those recorded on a nearby forested stream. Other studies which demonstrate the same effects of logging operations are those by Meehan et al. (1969), Patric (1970), Swift and Messer (1971), Brown (1969, 1970, 1972), and Brown and Krygier (1970, 1971). One of the most intensive studies of water temperature and logging was undertaken by Brown and Krygier (1970). They demonstrated that by patchcutting and leaving a buffer strip from 50-100 feet wide along a stream to provide the needed shade, no increased in temperature attributable to logging could be detected. Logging roads, skid trails, fire lanes, etc., have a significant influence on sediment input into nearby streams. A jammer logging operation (high density road system) in Idaho yielded as much as 12,400 2 tons/km in one season to the streams in one small watershed (Copeland 1965) while an insignificant turbidity increase resulted from skyline logging systems that use no roads (Fredrikses 1970). An in depth discussion

153 of the impacts of logging can be found in the proceedings of the Symposium on Trout Habitat Research and Management published by the Southeastern Forest Experiment Station, Ashville, North Carolina, 1975.

Water Depletions and Flow Requirements The quantity and quality of water in any river is critical to the maintenance of a viable ecosystem. Water withdrawals due to agriculture, domestic, and industrial use have been greatly increased, and the demand is steadily rising. Dam and reservoir water storage, channel changes and water withdrawals have greatly altered the flow regimes of the upper basin. Changes in the quantity and flow of water in the upper basin have had a significant impact on the fishes of this system. Reduced water quantities and reduction in flow have a direct effect on many factors relating to the well being of resident fishes including: space, temperature, dissolved oxygen, substrate aeration (necessary for egg development), and stream bank undercutting (creating or maintaining habitat). Wesche (1976) demonstrated in a three year study of several streams that 75 percent of all trout larger than six inches were found utilizing overhead bank cover while 50 percent of mailer trout were found in rubble-boulder areas. He indicated that competition may be a factor preventing smaller trout from using the same areas as larger individuals The availability of trout habitat in any particular stream can be used as a guide in establishing minimum flow reductions that could take place without severe impact (Wesche 1974). Flow depletion may have immediate and long-term effects. Immediate effects are those brought about by the reduction of stream size so that fish can no longer find adequate habitat. Distribution patterns adequately demonstrate that the four rare species of the lower and intermediate zones are restricted by river size. Depleting flow below the critical level would result in loss of the rare fish populations. The precise level considered critical for these species has not yet been determined. . Long-term effects of flow reduction include the parallel changes in channel hydraulic parameters which in turn alter stream bank cutting,

154 meander patterns, backwater building, sediment transport capacities, and velocities. With time, eddies, pools, riffles, river banks, and river beds along with depth, width, and flow pattern can be greatly altered. Reduction in flow in the upper basin has undoubtedly altered the available fish habitat, and these changes may have altered reproductive success. Since spawning occurs in the main channel it does not appear likely that the actual spawning area has been reduced. More likely the impact is due to loss of backwater nursery areas for the young. Also a shift in habitat may give a competitive advantage to introduced species. In comparing the Lower Green River with the lower zone of the upper Colorado River, we see that quantitatively, exotic species appear more abundant in the Colorado, while native species are more abundant in the Green (Holden and Stalnaker 1975a). The lower Green River is one of the least disturbed areas of the entire upper Colorado River basin. The sheer topography, narrow to non-existant stream banks, and rapid flows severely limit development by man. There are no roads, railroad settle- ments, or major towns along the Green from Oray, Utah (mouth of the Dushesne), to its confluence with the Colorado. It has remained relatively unchanged, and a higher percentage of native species would be expected. The Colorado River suffers more depletion loss, man's presence is not limited, and changes in the river are greater. It appears logical to hypothesize that the altered habitat of the Colorado River gives exotic species a competitive advantage, whereas the more natural habitat of the Green River favors the native species.

155 VI. URGENT NEEDS AND RECOMMENDED RESEARCH PRIORITY

Introduction During the course of this study it became clear that a great deal of information concerning the threatened and endangered species of the upper Colorado River basin did not exist. While studies on the upper Colorado basin fishes have not been lacking, such studies were usually funded for a specific purpose which was often unrelated to the problem of threatened or endangered species. In addition, many of the earlier studies were conducted before threatened or endangered status of a species was clear, with the result that all the information that might have been obtained on rare species was not recorded. As in any field of investigation, a considerable store of background material is necessary before an adequate overview of the problem appears. Without this overview, research is often directed at specific problems without identifying an overall goal. As an example, consider the habitat requirements of the Colorado Squawfish. Holden (1973) studied the habitat requirements, ecology, and life history of this species, and other studies (Prewitt and Wick for the USBLM) are presently underway. The squawfish is generally regarded as a large-river warm water species, but the question of how large is the required "large river" has not been directly addressed. In fact, professional opinion is even divergent on this point. The s general consensus is clearly that some rivers are at least adequately large to be classed as "large-river" habitat (e.g. the Green River in Desolation Canyon) and that some rivers are not presently large enough to classify as "large-river" habitat (e.g. the upper Dolores River), but the critically important grey area between the obvious caseu is subject to debate. Further, the reasons why the rare endemics use only "large-river" habitat are not clear and are also subject to debate. Since this grey area of river size is most likely to receive the majority of future water development impacts, it is an area deserving high research priority. Indirect answers based on the characteristics of river locations where the species is known to occur are unsaeisfacotry, because quantifi-

156 cation of these river sections is inadequate to allow prediction of impacts from future developments. Furthermore, the squawfish is already under stress, and characterizing its present habitat may accomplish little more than defining the lower limit at which it can exist. It is, in fact, unknown if the species will survive even if no further changes occur in the upper Colorado basin. Thus characterizing its present habitat may be characterizing a habitat below the minimum requirements for survival. Based on the lack of an inclusive, reliable data base, it would be presumptious to attempt to outline the research necessary to fill in all data gaps and answer all the unknowns concerning the rare fishes. In some instances the required research is obvious and straight forward. In other areas, only detailed research efforts would be of value. This effort would require the judgments and opinions of many individuals. The recent interest in the upper Colorado River basin and its rare and endangered fishes has brought to the attention of many agencies, schools, and individuals the need to gather the information necessary to answer the many concerns over the future of these fishes in the basin. The authors of the report feel that a concerted effort must be expended to accomplish the following: A. Identify those individuals who understand, are experienced with, and appreciate the upper Colorado River basin ecosystems. B. Hold a conference with these persons to: 1. Establish a goal upon which to focus operations. 2. Scrutinize all past data to identify the critical gaps or unsound results. 3. Identify and establish priorities for future research efforts. 4. Design efficient and realistic sampling programs. 5. Identify monies available. 6. Coordinate all research through one office. 7. Jointly compile and analyze all data. 8. Draw conclusions regarding what must be implement if the rare and endangered fishes are to survive and reproduce in the basin. 157 It is indeed essential to coordinate all future research in the basin. We can no longer afford to merely go our own way with our ideas with no attempt to join other researchers to design efficiency and avoid duplications. The best use of monies, time, and expertise can only be accomplished through coordinated efforts and mutual goals. Some of the general gaps in information are presented below as they apply to the specific species. Specific studies to fill these gaps may be required; however, frequently either ongoing research or proposed research can be modified or extended to provide the desired information more economically and more quickly than a specific study. The actual research and logistics determinations should be made by the group of individuals described above. Major information gaps are listed below by species. I. Colorado Cutthroat (Salmo clarki pleuriticus) A. How many pure populations still exist? Do the previously identified pure populations still remain as such? Are there any other undiscovered pure populations? What areas that potentially contain pure populations have not been studied? For the areas that have been studied and in which Colorado cutthroat were not found, how thorough was the study and how accurate were the species identifi- cations? B. Where are there areas that are sufficiently isolated or which could be isolated (by an artificial barrier) from waters containing exotic trouts to allow reestablishment of new pure Colorado cutthroat populations? Humpback Chub (Gila cypha) A. What is the true taxonomic (genetic) status of this species? Where do genetically pure populations of humpback chubs still exist? What are its actual habitat requirements; i.e. why are they found only in or adjacent to fast-water canyon areas? What are the mechanisms that maintain reproductive isolation and therefore prevent hybridization with the roundtail and bonytail chubs? What ecological

158 characteristics must be maintained in the environment to allow the species to persist? to increase? Can the species be successfully propagated in a hatchery? B. Because the species is presently so rare and is found only in areas extremely difficult to sample, answers to any of the questions above will be difficult (and therefore costly) to obtain. Bonytail Chub (Gila elegans) A. Where do genetically pure populations of bonytail chubs still exist? Where is reproduction of bonytail chubs still occurring? What are its detailed ecological requirements? What are the reproductive isolation mechanisms that inhibit hybridization with the roundtail and humpback chubs? Under what conditions do they breakdown? What are the environmental characteristics necessary for the success of the species? Can the species be artificially propagated? IV. Roundtail Chub (Gila robusta robusta) A. What factor(s) have recently caused the large decrease in abundance of the roundtail chub below Navajo Reservoir on the San Juan River? V. Colorado Squawfish (Ptychocheilus lucius) A. Are there resident populations of Colorado squawfish in major tributaries such as the Yampa, White, Gunnison, and Duchesne rivers? What are the reproductive (spawning and nursery) requirements of the Colorado squawfish? Where is reproduction successful at present? Can such reproductive habitat be created in areas where it is not now present? What factors in a "large river" cause it to be more favorable squawfish habitat than a smaller river? Where might this species be successfully reintroduced? Where does the Colorado squawfish presently exist? VI. Humpback (Razorback) Sucker (Xyrauchen texanus) A. Do humpback suckers spawn only over gravel bars at the head of islands that split the current or do they spawn in other locations? What are the requirements of nursery areas for this species? Why has there been an apparent increase in hybridization with the flannelmouth sucker? What characterizes the environment where hybridization is most common? least common? The questions posed are broad, but answers are necessary if the ecology and actions necessary for preservation of these endangered and threatened species are to be understood and implemented. The answers to some of these questions would involve a great deal of field research and may be prohibitive due to cost if they are addressed directly and individually. A better approach would be to combine research efforts so as to gain answers to questions in several areas or related to several species during a single field effort. For example, all the "large river" species occupy the same general habitat type, and research directed at one species can be directed at all the "large river" species for little additional cost and effort. In some instances, the field effort has, de facto, already been accomplished, and only additional laboratory work need be done. As a case in point, Kidd's collections of humpback chub intergrades in 1974 and 1976 (Kidd 1977) and recent collections by Kidd in the Colorado River and by the Utah Cooperative Fishery unit with the BLM in Green River have been the only verified occurrences of this species in recent years. This material would provide an excellent starting point for verification of the taxonomic status of the humpback chub. Only additional laboratory analyses are required. A second case is that the best example of a pure population of Salmo clarki pleuriticus known in Colorado is found in Northwater Creek, tributary to Parachute Creek. This population was discovered during baseline studies associated with oil shale development. The second best example of a pure population of Salmo clarki pleuriticus in Colorado is (was) known from the North fork of Cunningham Creek. This population

160 was discovered by studies made in connection with the Fryingpan-Arkansas diversion project, but the discovery was made after development. A negative impact (perhaps even extinction of this population) was assured because of the lack of thorough baseline studies before development. Such occurrences can be avoided in the future at very little cost to any given development if only the possibility of occurrence of Salmo clarki pleuriticus is recognized, and the required studies are designed to include a demonstration of the presence or absence of this species. It is apparent that non-native fishes pose a serious threat to several of the fishes endemic to the upper Colorado basin. This threat occurs via two mechanisms: the threat of loss of pure populations through hybridization as in the case of the Colorado cutthroat versus the introduced non-native cutthroat and rainbow trouts; and the threat of predation on the eggs and young, and of direct competition with endemic species as in the case of the Colorado squawfish and humpback sucker versus a host of introduced warm water species, especially the redside shiner. Fishery biologists in western states are often relatively untrained in the identification of non-game species, and in addition, job priorities prevent adequate collection of data on non-game species. It would be highly desirable to provide adequate funding for state fisheries biologists to collect more detailed and extensive surveys of the non-game species In conjunction with other game-fish related efforts. The last specific case to be mentioned is the current modification efforts of the penstocks of Flaming Gorge Dam. The water released from Flaming Gorge Reservoir has been so cold that even the growth of trout has been inhibited. The proposed modifications will allow reservoir discharge from selected depths and thus some control of the discharge temperatures. While an impact assessment was provided relative to these modifications, no follow-up monitoring study appears to be planned. Such a monitoring study is mandatory to document the effects of the modifications on the warm water species downstream of the cold water trout region as well as the effects on the trout fishery. Since the results of these modifications may greatly influence the design of

161 future dam outlet structures, a thorough study of the effects is important. While the effects of the modification on river temperatures can be ascertained merely by evaluation of USGS water data, the effects of various degrees of warming could also be correlated with range extensions of the warm water endemic species. This approach would also provide additional insight into the individual endemic species habitat requirements, thus furthering knowledge at relatively little additional cost. Undoubtedly other situations where research can be expanded or dovetailed with other study goals will occur in the future. It is just this kind of situation which a central group, through which all research is coordinated, can utilize to implement time and cost savings in obtaining the required information necessary to the survival of the threatened and endangered fishes in the upper Colorado basin. The first step is to establish a mechanism whereby the opinions and professional expertise of all knowledgeable, interested individuals can be utilized to identify, design, and undertake needed research efforts. LITERATURE CITED

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173 APPENDIX A

This paper was prepared by

Dr. Robert F. Behnke

For

The U.S. Fish & Wildlife Service

Albuquerque, New Mexico Name: Colorado River cutthroat trout Salmo Clarki pleuriticus Date Prepared: May, 1973

Order: Salmoniformes Family: Salmonidae

STATUS: RARE (DEPLETED)

I. Taxonomy A. Distinguishing characters: Typically, S. c. Pleuriticus is a brightly colored, large-spotted and fine-scaled cutthroat trout. Virtually no detailed taxonomic data on this subspecies has been published. Several samples from disjunct localities in the Colorado Cooperative Fishery Unit's collection exhibit con- sistant similarities and they form the basis for the following diagnosis: Spots, large and pronounced, concentrated mainly posteriorly; scales in lateral series (counted 2 rows above lateral line) 175-200+; scales above lateral line 38-48; vertebrae 61-63; pyloric caeca, mean values typically 30-40; gillrakers, 18-22; basibranchial teeth present, typically 1-15. Coloration may be gaudy, particularly on males in breeding season; red- crimson and orange and yellow colors emphasized. In some specimens, whole ventral region may be crimson.

B. Validity of subspecies and taxonomic problems. Cope (1872) described "Salmo pleuriticus" based on cutthroat trout specimens from the Green River, Wyoming, and from several localities in the Missouri and Columbia river basins. Of all the specimens considered by Cope in his description, the Colorado-Green River drainage was the only locality with an unnamed cutthroat trout at that time and the name pleuriticus has since been associated with the cutthroat trout of this basin. The diagnostic character used by Cope to describe pleuriticus was a ridge on the mid line of the skull - undoubtably an artifact of preservation. Jordan (1891) added some observations on trout he examined in Colorado. The specimens Jordan described from the Eagle River near Gypsum,

175 Colorado, are of particular interest. The Eagle River cutthroat collected by Jordan in 1889 had a profusion of very small spots - quite unlike the large spotted pleuriticus found elsewhere. Recent collections in headwater tributaries of the Eagle River have turned up only the typical large-spotted type of cutthroat trout (but these populations have been influenced by introductions).

C. Current activities. A M.S. thesis by Colorado Cooperative Fishery Unit student Gary Wernsman, now near completion, (May, 1973) details the taxonomy and distribution of S. c. pleuriticus.

II. Range and Distribution A. Historical: Throughout the upper Green and Colorado river system of Wyoming, Colorado, Utah and New Mexico (San Juan drainage), the southernmost distribution was the Dirty Devil River, Utah, in the west and the San Juan River, Colorado-New Mexico, in the east. Early records of S. c. pleuriticus from the headwaters of the Little Colorado River, Arizona, are erroneous. The trout originally found in the headwaters of the Little Colorado was Salmo apache, not S. c. pleuriticus (Miller, 1972).

B. Virtually gone in its pure form except in relatively few, isolated headwater tributary streams in Wyoming, Utah and Colorado. Based on evaluation of samples (personal data and in Mr. Wernsman's thesis) the following sites in the Green River drainage are judged to possess essentially pure S. c. pleuriticus. Headwaters Douglas Creek (trib. Little Snake R.) Medicine Bow National Firest, Carbon Co., Wyoming; Forth Fork Beaver Creek, Sublette Co., Wyoming; Rock Creek (trib. LaBarge Creek) Sublette Co., Wyoming; Little West Fork of the Black Fork, Wasatch National Forest, Summit Co., Utah. Three sites in the main Colorado River drainage, Northwater Creek (trib. to head of Parachute Creek) Garfield Co., Colorado; Cunningham Creek (trib. Frying Pay River) White River National Forest, Pitkin Co., Colorado and the very headwaters of the Colorado

176 River in Rocky Mountain National Park are judged to hold populations ideally approximating the diagnosis of S. c. Pleuriticus. Trout which phenotypically resemble cutthroat trout are not rare in the higher eleveation streams and lakes of the Colorado-Green River basin of Wyoming, Utah and Colorado. The overwhelming majority of these trout, however, have been influenced by, or are the direct result of, introductions. From the early 1900's to about 1950, millions of Yellowstone Lake cutthroat trout were stocked in Utah, Colorado and Wyoming (also rainbow trout were indiscriminantly spread throughout headwater areas). The present stocks of "native" trout propagated for stocking in the Colorado-Green River basin are: Strawberry Reservoir (Utah), a mixture of various cutthroat races and rainbow trout; Snake River Cutthroat (Wyoming) a fine-spotted form native to the Snake River and an undescribed subspecies; and Trappers Lake (Colorado). Based on a sample of 25 specimens made in 1970, the Trappers Lake cutthroat trout, despite past introductions of Yellowstone Lake cutthroat trout and rainbow trout is surprisingly close to the approximation of pure S. c. pleuriticus. It has not been greatly influenced by massive stocking of Yellowstone trout as believed by Snyder and Tanner (1959).

C. Ownership. Douglas Creek, Little West Fork of the Black Fork, and Cunningham Creek are on National Forests. The very headwaters of the Colorado River are in Rocky Mountain National Park. North Beaver Creek and Northwater Creek are on B.L.M. lands, but Northwater Creek is on the Naval Oil Shale Reserve section. Rock Creek has its very headwaters in Bridger National Forest but the main watershed is on B.L.M. or private holdings.

D. Competition from other uses (threatening factors). If all of the potential threats to the present populations are realized and if other pure populations of S. c. pleuriticus are not found, the status of this subspecies should change from rare to endangered. Oil shale development would pose a threat to the Northwater Creek trout. Cunningham Creek is part of the Bureau of Reclamation's Frying Pan-Arkansas water diversion project and its flow is scheduled for drastic reductions. Information on these populations has been made available to Colorado Division of Wildlife and the Bureau of Reclamation for impact considerations. The Little West Fork of the Black Fork population, now isolated from contamination by natural barriers, would be threatened by the proposed China Meadows Dam of the Bureau of Reclamation. If constructed, the irrigation reservoir would innundate the lower section of the stream with the barriers and allow rainbow trout to gain access and hybridization would almost certainly result. North Beaver Creek is on B.L.M. land which is a prime area for exploratory oil drilling.

III. Life History and Ecology A. Relative abundance. Most of the sites are small, headwater streams with populations of a few hundred to a few thousand fish.

B. Habitat description. Formerly occurring in a variety of habitats - large rivers and lakes and small tributaries. Now restricted to small, headwater tributary situations. The North Beaver Creek (Wyoming) population exists in a habitat badly degraded from overgrazing, but their persistence in this atypical cutthroat trout habitat indicated the ecological tolerance which might be expected of this subspecies, evolving in the highly variable environment of the upper Colorado-Green River drainage. All of the present habitats, with S. c. with the exception of the very headwaters of the Colorado River, are<=:, isolated from contamination by physical or biological barrieri.momp- sit No lakes are tributary to these streams (lakes are a prime

for stocking trout). The cutthroat trout in the very heaciwa

of the Colorado River occur about one mile above the hiito

178 site of Lulu City in Rocky Mountain National Park in about one mile of habitable water at an elevation from 9600-9700 ft. One mile below the collection site, at Lulu City, the trout population consists mainly of introduced species - brown, brook and rainbow trouts. There is a gradient of about 300 ft. in the Colorado River from Lulu City th the area where the sample was taken in 1970, but no obvious, absolute barriers were noted. It is difficult be believe that a pure cutthroat trout population has been maintained without benefit of a barrier preventing migration of rainbow trout and hybrids from downstream. This area should be curveyed again with a view of understanding how apparent purity is maintained in the cutthroat trout population at the very source of teh Colorado River. This population might serve as the nucleus for re-introductions of S. c. pleuriticus in Rocky Mountain Park.

C. Food and feeding. No detailed data but may be assumed to be characteristic of cutthroat trout in general - opportunistic on a wide range of invertebrates.

D. Reproduction: No indication that reproduction is any different from other subspecies of S. clarki. Spawns in spring or early summer depending on temperature in flowing water in clean gravel.

E. Interdependence and competition with other animal species. Originally, S. c. pleuriticus coexisted with several species of minnows, suckers and sculpins which were native to the Colorado drainage. Most of the native fauna, as with the cutthroat trout, have been replaced by introduced fishes. The greatest impact causing the drastic decline of the native cutthroat has been from other trout species - displacement by brown and brook trouts and hybridization with rainbow trout. Most of the known populations of S. C. pleuriticus exist in complete isolation from all other fishes. The cutthroat trout in Douglas Creek,

179 Wyoming, however coexists with brook trout and dominate them in abundance by a ratio of about 10-1 (1968 data). This fact indicates that under optimum environmental conditions, S. c. pleuriticus can coexist with introduced trout and indeed be the dominant species - as is also the case of S. C. virginalis and Salmo trutta in the Rio Chiquito in New Mexico.

IV. REsearch Needs (Management recommendations) Special consideration will be necessary to protect and perpetuate those populations under threat from reclamation projects, oil shale development and oil exploration. The B.L.M. land of the foothills area of the Green River drainage in Sublette Co., Wyoming, holds considerable promise for habitat restoration projects. Protection from overgrazing should result in rapid revegetation, stream bank stabilization, reduced siltation, reduced temperatures and increased food supply. Those watersheds with introduced trout or hybrids can be treated with toxicants and fish from North Beaver Creek and Rock Creek can be transplanted to establish new populations. A proposed plan for habitat improvement with a goal of enhancing the survival and abundance of S. c. pleuriticus has been developed by the Casper, Wyoming, B.L.M. office. Possibilities exist for re-introductions of S. c. pleuriticus in the Colorado River drainage of Rocky Mountain Park from transplants of the present population in the headwaters of the Colorado River in the Park. The 1972 Annual Project Report of the Fishery Management Program of Rocky Mountain National Park, prepared by James Mullen, U.S. Bureau of Sport Fisheries and Wildlife biologist, Vernal, Utah, reviews the drainage of the Park and their fisheries potential. The upper Colorado basin of Utah, Colorado and Wyoming covers an immense geographical area. Collections have generally sampled the most likely sites where pure populations may have persisted, but a complete survey of potential native trout populations is far from completed and future samplings should be expected to discover other pure populations of S. c. pleuriticus.

V. Authorities Robert Behnke, Colorado Cooperative Fishery Unit, Colorado State University, Ft. Collins, Colorado 80521. The Coop. fish collection maintains a large series of trout samples from the Colorado drainage including those mentioned in this report. Two mimeographed Coop. Unit reports have been prepared on S. c. pleuriticus (see references). James Mullen, U.S. Bureau of Sport Fisheries and Wildlife, Vernal, Utah. Mr. Mullen coordinates fisheries programs in Rocky Mountain National Park. Included in teh 1973 objectives are plans to re-establish pure populations of native trout (S. c. stomias and perhaps S. c. pleuriticus) in Park waters. Annotated Bibliography

Behnke, R.J. 1968. Progress Report: Cutthroat trout of the Rio Grande and Colorado river basins. Colo. Coop. Fish. Unit Rare and Endangered Species Rept., mimeo: 7 p. Data and comparisons of S. c. pleuriticus and S. c. virginalis. . 1970. Rare and Endangered Species Report: The native trout of the Colorado-Green River basin, Salmo clarki pleuriticus. Colo. Coop. Fish. Unit, Colo. St. Univ., Ft. Collins, Colo. 80521. Further information on status of S. c. pleuriticus. Cope, E.D. 1872. Report on the reptiles and fishes obtained by the naturalists of the expedition. U.S. Geol. Surv. Montana and adjacent territories (Hayden's Surv.); part 4, botany and zoology: 467-476. Original description of "Salmo pleuriticus". Drummond, R.A. 1966. Reproduction and harvest of cutthroat trout at Trappers Lake, Colo. Colo. Dept. Game, Fish and Parks Spec. Rept. 10: 26 p. Although the Trappers Lake cutthroat has been influenced by hybridization, they are predominantly S. C. pleuriticus. Jordan, D.S. 1891. Report of the explorations in Colorado and Utah during the summer of 1889, with an account of the fishes found in each of the river basins examined. Bull. U.S. Fish Comm., 9:1-40. Obser- vations on S. c. pleuriticus and other Colorado River fishes. Miller, R.R. 1972. Classification of the native trouts of Arizona with the description of a new species, Salmo apache. Copeia (3):401-422. Corrects former distribution record of S. c. pleuriticus in Arizona. Fig. 1 illustrates original range of S. c. pleuriticus. Snyder, G.R., and H.A. Tanner. 1960. Cutthroat trout reproduction in the inlets to Trappers Lake. Colo. Dept. Game and Fish Tech. Bull. 7:4 86 p. The authors believed that introductions of Yellowstone Lake cutthroat trout had a considerable influence on the trout under study. A sample of trappers Lake cutthroat trout in 1970 revealed no apparent influence of Yellowstone Lake stock in several characters, examined.

182 Wernsman, G. 1973. The native trouts of Colorado. M.S. Thesis, Colo. State Univ. (in final stages of completion, May 1973). Comprehensive survey of information on S. C. pleuriticus and comparisons with S. C. stomias and S. c. virginalis.

183 50272-lot REPORT DOCUMENTATION 1. REPORT NO. 3. Recipient's Accession No. FWS/OBS-77/62 PAGE PB 279 545 4. Title and Subtitle An Evaluation of the Status, Life History, and 5. Report Date Habitat Requirements of Endangered and Threatened Fishes of the September1977 Upper Colorado River System (FWS/OBS-77/62) 6.

7. Author(s) Robert BehnkeTr 8. Performing Organization Rept. No. Timothy W. Joseph, James A. Sinning, Paul Holden

9. Performing Organization Name and Address 10. Project/Task/Work Unit No. Ecology Consultants, Inc. WELUT Project 024-76 1716 Heath Parkway 11. Contract(C) or Grant(G) No. Fort Collins, Colorado 80526 (C) 14-16-0009-77-012 and BioWest, Inc. (G)

12. Sponsoring Organization Name and Address 13. Type of Report 8. Period Covered Western Energy and Land Use Team Office of Biological Services, U.S. Fish & Wildlife Service 2625 Redwing Road, Fort Collins, Colorado 80526 14.

15. Supplementary Notes EPA-IAG-D7 E685 Part 2 of 3 parts Western Water Allocation Project Funds

16. Abstract (Limit: 200 words) The focus of this report are the endangered and threatened fishes, but a full appreciation would not be possible without an adequate knowledge of the ecosystem in which they live. The six major sections of the report are: abiotic components, biological components, species description,river basin descriptions, major factors inducing environmental change, and urgent needs and recommended research priorities.

17. Document Analysis a. Descriptors Fish Endangered Species Colorado River Threatened Species Fish Habitat

b. Identifiers/Open.Ended Terms Colorado Wyoming Utah New mexico

c. cosim Field/Group Arizona

18. Availability Statement 19. Security Class (This Report) 21. No. of Pages Unclassified 194 Release Unlimited s i 8 . * tRiniegISE1ba' e) Ot!Xdb/MF:A01 (See ANSI-239.18) ornomALFomd272 (4-77) (Formerly NTIS-35) 184 Department of Commerce

41. U. S. GOVERNMENT PRINTING OFF ICE 1978 - 777-138/3117 Reg. 8