Biological Assessment 

for 

Redlands Water and Power Company 

Fish Screen 

on the Gunnison River 

Prepared by 

U.S. Bureau of Reclamation 

Western Colorado Area Office 

Grand Junction, Colorado 

For 

Upper Colorado River Basin Endangered Fishes Recovery Program 

U.S. Fish and Wildlife Service 

Denver, Colorado 

August 2003 
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TABLE OF CONTENTS 

INTRODUCTION......................................................................................................................... 1

REDLANDS WATER AND POWER COMPANY ................................................................................. 1 

UPPER COLORADO ENDANGERED FISHES RECOVERY PROGRAM ................................................. 4 

PROJECT PURPOSE AND STATUS........................................................................................ 5

PURPOSE AND NEED FOR THE PROJECT.......................................................................... 5

PROJECT COMPONENTS ........................................................................................................ 6

DESCRIPTION OF THE AFFECTED ENVIRONMENT ...................................................... 7

ALTERNATIVES INCLUDING THE PROPOSED ACTION ............................................... 9

NO-ACTION ALTERNATIVE .......................................................................................................... 9 

PUMP REPLACEMENT ................................................................................................................... 9 

FISH SCREEN-PREFERRED ALTERNATIVE..................................................................................... 9 

DETERMINATION OF ANTICIPATED INCIDENTAL TAKE LEVELS FOR RWPC 

OPERATIONS AND THE FISH SCREEN. ............................................................................ 10

ENDANGERED COLORADO RIVER FISHES .................................................................... 10

COLORADO PIKEMINNOW ................................................................................................. 12 

Colorado Pikeminnow Distribution-Colorado River............................................................ 12

Colorado Pikeminnow Distribution-Gunnison River ........................................................... 14

Colorado Pikeminnow Population Augmentation ................................................................ 15

Colorado Pikeminnow Habitat Use...................................................................................... 16

Colorado Pikeminnow Reproduction.................................................................................... 17

RAZORBACK SUCKER ......................................................................................................... 19 

Razorback Sucker Distribution-Colorado River................................................................... 19

Razorback Sucker Distribution-Gunnison River .................................................................. 20

Razorback Sucker Population Augmentation ....................................................................... 21

Razorback Sucker Habitat Use ............................................................................................. 24

Razorback Sucker Reproduction........................................................................................... 25

Humpback Chub and Bonytail.............................................................................................. 26

Bonytail Population Augmentation....................................................................................... 26

EFFECTS ON ENDANGERED COLORADO RIVER FISHES .......................................... 28

BALD EAGLE ............................................................................................................................ 28

Bald Eagle Habitat Preference............................................................................................. 29

Bald Eagle Distribution and Abundance .............................................................................. 29

EFFECTS ON BALD EAGLE ................................................................................................. 30 

INDIRECT PROJECT AND CUMULATIVE EFFECTS ..................................................... 30
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CONSIDERATION OF FEDERALLY THREATENED AND ENDANGERED PLANTS30

CRITICAL HABITAT ............................................................................................................... 31

MINIMIZING AND MITIGATING IMPACTS TO THE COLORADO RIVER 

ENDANGERED FISHES........................................................................................................... 31

SUMMARY AND CONCLUSIONS ......................................................................................... 33

REFERENCES............................................................................................................................ 34

LIST OF FIGURES 

Frontispiece Map-Project Location Map 

Figure 1-USGS Quadrangle Map with Project Area ...................................................................... 2 

Figure 2-USGS Quadrangle Map with RWPC Service Area ......................................................... 3 

Figure 3-Habitat Types within RWPC Service Area...................................................................... 8 

Figure 4-General Site Plan Drawing............................................................................................. 11 

Figure 5-Distribution of Colorado Pikeminnow in the Colorado and Gunnison Rivers. ............. 14 

Figure 6-Gunnison River Colorado Pikeminnow Distribution..................................................... 16 

Figure 7-Potential Colorado Pikeminnow Spawning Sites in the Colorado and Gunnison Rivers.

............................................................................................................................................... 19 

Figure 8-Razorback Sucker Distribution in the Colorado and Gunnison Rivers.......................... 21 

Figure 9-Larval and Junvenile Razorback Sucker Collections from the Colorado and Gunnison 

Rivers. ................................................................................................................................... 22 

Figure 10-Distribution of Humpback Chub and Bonytail in the Colorado and Gunnison Rivers.27 

Figure 11-Upper Colorado River Basin Endangered Fishes Critical Habitat............................... 31 
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INTRODUCTION 

Redlands Water and Power Company 

The Redlands Water and Power Company (RWPC) was established to supply irrigation water 

from the Gunnison River to the Redlands community near Grand Junction, Colorado. Gunnison 

River water is diverted at the Redlands Diversion Dam approximately 2.3 mile upstream of the 

Gunnison River’s confluence with the Colorado River (Figure 1). RWPC constructed the 

diversion dam in 1918 and has since modernized and updated the structure. The concrete dam is 

8.5 feet high and consists of a 312-foot-long spillway with a 6-foot-wide crest and two 10-footwide by 6-foot-high sluice gates. A flow of 850 cubic feet per second (cfs) is diverted through 

four 14-foot-wide headgates on the west side into the Redlands Power Canal. The Redlands 

Power Canal is approximately 4 miles in length and terminates at Redland’s electric pumps and 

power plant. Pumped water is lifted to smaller distribution pipelines and canals to service the 

Redlands community. Water that passes through the power plant is discharged directly into the 

Colorado River. Figure 2 shows RWPC’s service area, which incorporates the Redlands 

Diversion Dam, Redlands Power Canal and delivery systems, and RWPC’s pumps and power 

plant. 

During the irrigation season (April-October), water is lifted 120 feet by electric pumps to supply 

water to RWPC shareholders or used for hydropower generation at the Redlands Power Plant. 

During the remaining portions of the year, water is diverted only to the Redlands Power Plant. 

In 1983, the Federal Energy Regulatory Commission (FERC) exempted RWPC from licensing 

under FERC regulations. This exemption required that fish passage be allowed around the dam. 

The Redlands Diversion Dam is a recognized barrier to upstream endangered fish movements; 

and the operation of the Diversion Dam, Redlands Power Canal, electric pumps and power plant 

can all result in the unauthorized incidental take of all life stages of the Colorado River 

endangered fishes. To assist in recovery efforts for the Colorado pikeminnow (Prychocheilus 

lucius) and razorback sucker (Xyrauchen texanus), RWPC has worked with the Upper Colorado 

River Endangered Fishes Recovery Program (Recovery Program) to minimize take. To mitigate 

for unavoidable incidental take of the Colorado pikeminnow and razorback sucker, Redlands has 

agreed to address potential impacts to Colorado pikeminnow and razorback sucker associated 

with RWPC operations. This biological assessment was prepared in consultation with the U.S. 

Fish and Wildlife Service (Service) and Recovery Program, and RWPC. 
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Figure 1-USGS Quadrangle Map with Project Area 
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Figure 2-USGS Quadrangle Map with RWPC Service Area
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Upper Colorado Endangered Fishes Recovery Program 

The Upper Colorado River Endangered Fishes Recovery Program (Recovery Program) was 

established in 1988 to recovery four endangered Colorado River fish within the Upper Colorado 

River Basin. The endangered Colorado River fishes include the Colorado pikeminnow, 

razorback sucker, humpback chub (Gila chypha), and bonytail (Gila elegans). The Recovery 

Program is comprised of private, State and Federal interests and is designed to recover the 

endangered fishes, while providing for water development and use to proceed in a manner 

compatible with applicable State, and Federal laws. In 1996, the Recovery Program constructed 

a fish passageway around the Redlands Diversion Dam to allow endangered and native fish 

movement upstream. On behalf of the Recovery Program, the Bureau of Reclamation 

(Reclamation) constructed the fish passageway, and the Service operates the fish passageway to 

prevent the movement of non-native fish species upstream. The dam was identified by the 

Recovery Program as a barrier to fish movement and was included as an action item in the 

Recovery Program’s Recovery Action Plan (RIPRAP). The RIPRAP also includes action items 

to construct and operate a fish screen in the Redlands Power Canal to minimize endangered fish 

canal entrainment and incidental take. 

The RWPC currently owns lands to be used to construct the fish screen and the Recovery 

Program will provide funding as authorized by Congress to construct the fish screen. 

 

This biological assessment (BA) includes commitments for mitigation of all reasonably 

anticipated incidental take within the RWPC’s service area. The BA discusses methods to avoid, 

minimize, and mitigate impacts to the Colorado pikeminnow and razorback sucker. The 

mitigation section of this document provides commitments for minimizing the incidental takings 

the Colorado pikeminnow and razorback sucker within RWPC’s service area. 

RWPC has requested extended coverage for incidental take and RWPC’s depletions in 

conjunction with Reclamation’s Section 7 consultation for the construction and operation of the 

Redlands fish screen. Extended Section 7 coverage would allow RWPC to continue its historic 

diversions and depletions, and allow for the incidental take of Colorado pikeminnow and 

razorback sucker within RWPC’s service area. The Recovery Program will complete all 

mitigation, monitoring, and conservation measures. Other mitigation measures (i.e. operation of 

the Redlands fish passageway and fish screen) within RWPC service area will also require 

incidental take coverage. After sunset of the Recovery Program, any “take” within the said 

geographic boundaries will require reauthorization by the Service unless previously deferred 

based on agreements between the Service, RWPC and the Recovery Program. The intent is for 

the Recovery Program to continue for as long as the Secretary of Interior recommends and 

Congress appropriates funds. 
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PROJECT PURPOSE AND STATUS 

The purpose of the Redlands fish screen is to reduce the potential for incidental take of Colorado 

pikeminnow and razorback sucker associated with continued RWPC’s operations, and to provide 

mechanisms to avoid, minimize, and mitigate for any incidental take of the Colorado 

pikeminnow and razorback sucker within the RWPC service area. The Redlands fish screen is 

listed in the Recovery Program’s RIPRAP as an item needed to assist in the recovery of the 

endangered Colorado River fishes. 

Informal consultation with the Service identified the following federally listed species, which 

may occur within the project area, which includes the RWPC service area: 

Colorado pikeminnow (Prychocheilus lucius) 

 razorback sucker (Xyrauchen texanus) 

 bonytail (Gila elegans) 

 humpback chub (Gila chypha) 

 bald eagle (Haliaeetus leucocephalus) 

PURPOSE AND NEED FOR THE PROJECT 

The Recovery Program has identified a need to screen the Redlands Power Canal to reduce the 

potential for take of Colorado pikeminnow and razorback sucker from continued RWPC 

operations. The purpose of the project is to assist in endangered Colorado River fishes recovery 

efforts and to allow continued operations of the RWPC to deliver irrigation water supplies and 

generate hydroelectric power to meet the current and future needs of the Redlands community 

southwest of Grand Junction, Colorado. 

The Service and Recovery Program identified the Redlands Diversion Dam as a complete barrier 

to all fish movement. In 1996, the Recovery Program, in cooperation with RWPC, constructed a 

fish passageway around the Redlands Diversion Dam. The Service has operated the fish 

passageway since 1996 to allow endangered fish movement upstream to access additional critical 

habitat. Also, the fish passageway allows other native fish to move upstream but prevents nonnative fish movements with the operation of the selective passage (fish trap). From 1996 to 

2000, the Service reported 43,123 fish comprising 19 different species and three catostomid 

hybrids used the Redlands fish passageway. A total of 40,274 native fish, including 51 Colorado 

pikeminnow, used the passageway during this period (Burdick, 2001a). Additionally, in 2001, 

razorback sucker began using the passageway. Five razorback sucker were documented using 

the Redlands fish passageway in 2001 (Burdick, 2002). 

The Service has also identified the potential for incidental take of Colorado pikeminnow and 

razorback sucker as a result of diversion of the Gunnison River at the Redlands Diversion Dam 
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into the Redlands Power Canal. Fish could be incidentally taken at Redland’s electric pumps, 

power plant, during canal dewatering, or transported through ditches to irrigated fields. 

PROJECT COMPONENTS 

The Redlands Water and Power Company was established to deliver water to an area southwest 

of the confluence of the Gunnison and Colorado Rivers (known as the Redlands),. In 1918, 

RWPC moved its diversion dam on the Gunnison River, down stream 1⁄4 mile to its present 

location. The diversion dam is approximately 2.3 miles upstream of the Gunnison River’s 

confluence with the Colorado River. Gunnison River water is diverted at the dam into the 

Redlands Power Canal, which terminates at the Redlands Power House (electric pumps and 

power plant) and returns water to the Colorado River. About 70 cfs is pumped and delivered to 

the Redlands community for irrigation uses. Table 1 provides additional information on 

Redlands Facilities. 

Table 1.0 – Redlands Water and Power Facilities and Operations 

Feature Description Capacity 

Redlands Diversion Dam 8.5-foot high diversion dam constructed 

in 1918 that spans the Gunnison River, 

consists of two 10-foot-wide by 6-foot 

sluice gates and 14-foot-wide head gates 

Capable of diverting 750 cfs of 

the Gunnison River 

Redlands Power Canal Earthen canals and laterals 26 miles in 

length.8 Canal flows are monitored at a 

gage station operated by the State of 

Colorado 

850 cfs 

Redlands Power House 

- Pumps 

 - Power Plant 

Electric pumps capable of lifting water 

120 feet 

1 Generator 

~70 cfs 

1.5 Megawatts 

Water Rights 670 cfs-priority date July 31, 1905 

80 cfs-priority date June 26, 1941 

100 cfs-priority date 1995 

Allowed Uses: irrigation, 

domestic stock, and power 

generation 

Allowed Uses: irrigation and 

power generation 

Allowed Uses: All the above. 

Redlands Depletions Dewatering of Gunnison River (up to 

750 cfs, of which ~690 cfs is returned 

directly to the Colorado River). 

2.3 Miles 
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DESCRIPTION OF THE AFFECTED ENVIRONMENT 

RWPC facilities are located in Mesa County in western-central Colorado. The diversion dam is 

located on the Gunnison River approximately 2.3 miles southwest of the City of Grand Junction. 

The Redlands Power Canal parallels the Gunnison River for about 4 miles and terminates at the 

Redlands Powerhouse. At the Powerhouse, approximately 70 cfs of water used for irrigation is 

electrically pumped to an upper terrace along the Colorado River to the Redlands and the 

remaining ~680 cfs is used to generate hydroelectric power and is returned to the Colorado 

River. The irrigation season lasts approximately 6 months from April 15 to October 15. During 

the remaining 6-month period, the power canal is used solely for hydroelectric power. 

Mesa County has a population of about 120,000. Historically, land use in the Redlands area 

evolved much the same as other areas in the Grand Valley near the City of Grand Junction. 

Agriculture dominated as semi-arid lands were converted to productive farmland with the 

addition of irrigation. Gradually, due to the close proximity to a major city, residential 

development increased. Small subdivisions and many residential corridor developments are 

scatter throughout the Redlands area. The remaining land use is now residential with scattered 

agricultural parcels. Gravel mining, other water development projects on the Gunnison and 

Colorado Rivers (i.e. Reclamation’s Uncompahgre Project and Aspinall Unit on the Gunnison 

River, and Grand Valley Project on the Colorado River), and other land use changes have altered 

the Colorado and Gunnison rivers in the project area and decreased the size of the floodplain. 

The RWPC’s service area is bound by the Gunnison River from the east, the Colorado River to 

the north, and the Colorado National Monument to the south, and includes approximately 10,625 

acres (Figure 2). 

Colorado pikeminnow and razorback sucker habitat within the RWPC service area is limited to 

the Gunnison and Colorado Rivers. These river reaches are within the designated critical habitat 

for both species, which includes the river and its 100-year floodplain (USFWS, 1994). 

Historically, RWPC could divert all or a significant portion of the Gunnison River into the 

Redlands Power Canal. RWPC has a senior water right for 750 cfs, and a junior water right for 

an additional 100 cfs. In 1996, Reclamation entered into a temporary agreement with the 

Colorado Water Conservation Board to deliver water from the Aspinall Unit to ensure that a 300 

cfs minimum was maintained downstream of the Redlands Diversion Dam in the months of July 

through October for the benefit of the Colorado pikeminnow and razorback sucker. This 

agreement will be superceded by arrangements made in the future Aspinall Unit Section 7 

consultation. The 300 cfs below Redlands allows for the operation of the Redlands Fish Passage 

and allows endangered fish access in a reach of the Gunnison River below Redlands that would 

prevent fish movement if Gunnison River flows decreased below 250 cfs below the Redlands 

Diversion Dam. In 1996, the Recovery Program constructed the Redlands Fish Passageway, 

which was been described previously in Section 2.1 of this BA. Since completion of the fish 

passageway, the Service has operated the fish passageway from March through October each 
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year. Both Colorado pikeminnow and razorback sucker have used the fish passageway at the 

Redlands Diversion Dam to access the Gunnison River upstream (Burdick, 2001a). 

During the drought of 2002, RWPC entered into an agreement with the Colorado River Water 

Conservation District to forego power production in lieu of payment for power interference to 

prevent a “river call” to upstream junior water users. This also allowed for the continued 

operation of the fish passageway and sufficient flows downstream of the dam during the drought. 

Approximately 720 acres of irrigated agriculture, 20 acres of wetlands, 850 acres of riparian 

habitat, 4,150 aces of upland habitat, 270 acres of gravel mined areas, and 4,615 acres of 

residential and commercial development are located within the RWPC’s service area (Figure 3). 

Figure 3-Habitat Types within RWPC Service Area 
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ALTERNATIVES INCLUDING THE PROPOSED ACTION 

This section briefly discusses a range of project alternatives, including all “reasonable 

alternatives” considered for the proposed project and those “other alternatives” eliminated from 

detailed study. Included is a discussion of how and why the proposed alternative was selected 

for detailed study and why other alternatives were eliminated. This is section provided as 

background information on various alternatives examined and is not intended to fulfill the 

National Environmental Policy Act requirements. For further information regarding alternatives 

examined for the proposed project, see the Environmental Assessment for the Redlands Fish 

Screen in the Redlands Power Canal. 

No-Action Alternative 

Under the No-Action Alternative, RWPC would not implement measures to address incidental 

take during RWPC operations. A fish screen would not be installed in the Redlands Power 

Canal, however the operation of the fish passageway at the Redlands Diversion Dam would 

continue. RWPC would not receive Recovery Program funding to operate and maintain the fish 

screen, and maintain the fish passageway. 

The unauthorized incidental take of Colorado pikeminnow and razorback sucker would continue. 

This alternative does not meet the need for the proposed project. 

Pump Replacement 

The pump replacement alternative would replace the existing hydro-pumps used to lift irrigation 

and municipal water supplies up to the Redlands with electric pumps. This alternative would 

reduce the volume of water diverted at the Redlands Diversion Dam from 750 cfs to 70 cfs. 

While this alternative would provide some benefit, incidental take would still occur at the 

electric pumps and RWPC would not be able to put their entire water right for beneficial use 

generating hydroelectric power. Junior water rights upstream could divert additional water from 

the Gunnison River and negatively affecting upstream critical habitat. Because this alternative 

would not reduce the likelihood of incidental take and possibly dewater critical habitat upstream 

of the Redlands Diversion Dam, it was discarded from further discussion. 

Fish Screen-Preferred Alternative 

This alternative would construct a fish screen in the Redlands Power Canal to prevent canal 

entrainment and incidental take of adult and sub-adult Colorado pikeminnow and razorback 

sucker. The Recovery Program would design and construct the fish screen and provide operation 

and maintenance funding to RWPC for the fish screen. RWPC would assume ownership of the 

fish screen and could also operate the screen without Recovery Program funding. 
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RWPC would also assume ownership of the Redlands fish passageway. The Service would 

continue to operate the fish passageway and RWPC would perform maintenance activities with 

funding provided by the Recovery Program. 

The fish screen was designed based on the biology and characteristics of the Colorado 

pikeminnow and razorback sucker. Figure 4 provides a general site plan for the fish passage 

structure, which includes the fish screen, a bypass channel, and a fish return pipeline. The fish 

screen would be a “V-Type” configuration with each leg of screen being 160 feet long. The 

screen is designed for a total diversion flow of 890 cfs, returning 40 cfs for the fish return pipe, 

for a total screened flow of 850 cfs. The fish pipeline would be constructed using 36 inch PVC 

pipe with a total length of approximately 460 feet. Upstream and downstream bulkheads would 

be used for isolation during icing and other times when the fish screen is bypassed. 

DETERMINATION OF ANTICIPATED INCIDENTAL TAKE LEVELS 

FOR RWPC OPERATIONS AND THE FISH SCREEN. 

The potential for incidental take of Colorado pikeminnow and razorback sucker is anticipated to 

result from the continued RWPC operations and diversions of water from the Gunnison River via 

the Redlands Diversion Dam. Depletions from the Gunnison River are also anticipated to have 

an adverse affect on Colorado pikeminnow and razorback sucker and their designated critical 

habitat within the Gunnison and Colorado Rivers. RWPC would reduce the level of incidental 

take associated with diversions by screening adult and sub adult fish, and returning these fish to 

the Gunnison River and continue selective fish passage upstream of the diversion dam. The 

selective fish passage would prevent non-native fish species from moving upstream and 

occupying additional habitats. 

The incidental taking of adult and sub-adult Colorado pikeminnow and razorback sucker would 

likely occur when the fish screen is not operating because of fish screen icing, fowling, or 

mechanical failure. In addition, current technology allows for screening of only adult and sub 

adult fish. The current standard fish screen size of 3/32” would not prevent larval fish and eggs 

from continuing down the Redlands Power Canal, passing through the pumps and generating 

turbines, and onto irrigated properties. The area of impacts to Colorado pikeminnow and 

razorback sucker includes approximately 2.3 miles (80 acres) of the Gunnison River, XX miles 

of canal and laterals, 850 acres of riparian floodplain habitat, 720 acres of irrigated agricultural 

lands, and 4,615 acres of residential and commercial development. 

ENDANGERED COLORADO RIVER FISHES 

The Colorado River Basin originally supported a depauperate fish fauna with 36 species from 20 

genera and 9 families. Of these 36 native species, 64 percent were endemic to the basin and only 

eight were found in both upper and lower portions of the basin. Because of widespread 
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Figure 4-General Site Plan Drawing 
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introductions, over 100 species are now found in the basin (Carlson and Muth, 1989). In recent 

years, Tyus et al. (1982) documented 13 native and 42 non-native fishes reported from the 

Colorado River and its tributaries upstream of Lake Powell. Four native fish species to the large 

rivers of the Colorado River Basin are listed as endangered under the Endangered Species Act of 

1973. The endangered fish are the Colorado pikeminnow, razorback sucker, humpback chub, 

and bonytail. The Colorado pikeminnow and razorback sucker occur within the project area and 

are discussed in detail in this section. The humpback chub and bonytail do not occur within 

these reaches of the Colorado and Gunnison rivers, and are not discussed in great detail. 

This section is not intended to be an exhaustive literature review of the four endangered species, 

but to provide an overview of the known information that is pertinent to the fish screen and 

RWPC’s operations. Literature reviews of the life history and ecology of these species are 

available in Bestgen (1990), Minckley et al. (1991), Tyus (1991) and Muth et al. (2000). 

COLORADO PIKEMINNOW 

Colorado pikeminnow (formerly known as Colorado squawfish is a large piscivorus cyprinid 

endemic to the Colorado River Basin (Minckley 1973) and is one of four large cyprinids of the 

genus Ptychocheilus native to the western United States (Robins et al., 1991). 

Colorado pikeminnow is the largest of the four and reportedly reached lengths approaching 1.8 

m and weights of 45 kg (Minckley, 1973) during European settlement of the west. The largest 

Colorado pikeminnow captured in recent years was 960 mm long and exceeded 5-kg (McAda, 

2000). In 2002, an adult female Colorado pikeminnow 940 mm long and 7.6 kg was captured at 

the Redlands fish passageway. 

The species was once widespread in the large rivers of the Colorado River Basin, but it was 

eliminated from the basin downstream of Lake Powell by the late 1960s (Minckley, 1973). 

Although it still exists in the upper basin, its range has been reduced by construction of large 

reservoirs that eliminated habitat and changed downstream water quality (e.g. Vanicek et al. 

1970) and construction of instream barriers that blocked access to historic range (Burdick and 

Kaeding, 1990). The reduced habitat and declining number of fish occupying the remaining 

habitat prompted the species to be included as endangered when a list of endangered species was 

published in 1967 (USFWS, 1967). 

Colorado Pikeminnow Distribution-Colorado River 

Colorado pikeminnow are distributed throughout the Colorado River from Price Stubb Dam, an 

impassible barrier at the upper end of the Grand Valley (RM 188.3), downstream to Lake Powell 

(Figure 5, Osmundson and Burnham 1988). The Recovery Program is planning construction of 

a fish passageway at the Price Stubb Diversion Dam in 2005. The Grand Valley Project 

Diversion Dam, an additional barrier upstream of the Price Stubb Diversion Dam, will have a 

fish passage constructed in 2004. The removal of these two barriers will allow Colorado 

pikeminnow access to about 50 miles of critical habitat upstream to Rifle, Colorado. 
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Although pikeminnow use the entire river, there are distinct differences in distribution among 

age classes. In general, most adults are found in the upper reaches of the river and most subadults, juveniles, and young-of-year (YOY) are found in the lower reaches (McAda, 2000; 

Valdez et al. 1982b; Archer et al. 1985; McAda and Kaeding 1991; Osmundson et al. 1997). 

Osmundson and Burnham (1998) conducted an intensive river-wide study using mark recapture 

to estimate the population size of sub adult (250-500 mm long) and adult Colorado pikeminnow 

(>500 mm long) in the Colorado River. The river was divided into two sub reaches —

Westwater Canyon upstream to the Price Stubb Diversion Dam (RM 125-188) and confluence 

with the Green River upstream to Westwater Canyon (RM 0-113). They estimated that the 

average population size in 1991—1994 was 253 (95% CI, 161-440) for the upper reach and 334 

(95% CI, 196-604) for the lower reach. 

Although most adults were captured from the upper river, they were not distributed equally 

throughout the reach. Catch rates in two segments of the upper reach—known as the 18-mile 

reach (RM 154-171) and the 15-mile reach (RM171-185)—where five to six times higher than in 

the lower third of the reach (McAda, 2000). 

Density and distribution of YOY Colorado pikeminnow have been monitored in the Colorado 

River since 1982 (McAda and Ryel, 1999). Density has been highly variable over that period, 

but YOY have been captured every year since monitoring began (McAda, 2000). YOY 

Colorado pikeminnow were found throughout the Colorado River downstream from the 

confluence with the Gunnison River, but were most abundant in the 65 miles between Moab, 

Utah and the mouth of the Green River (McAda, 2000). 

Although they did not find a significant difference in population size among the 4 years of the 

study (1991-1994), Osmundson and Burnham (1998) noted what appeared to be a general 

increase in the number of adult pikeminnow in the upper river over time. Catch rates increased 

steadily in the upper reach during that period. Osmundson and Burnham (1998) attributed this to 

recruitment of a large group of individuals from 1985-1987 year-classes recruiting to young 

adulthood and moving into the upper reach. The strong year-classes of young adults 

corresponded to high density of YOY Colorado pikeminnow in 1985-1986. An increasing 

population in the Colorado River during the mid 1990s was also implied by a constant increase 

in catch per unit effort during spring Interagency Standardized Monitoring Program (ISMP) 

electrofishing (McAda et al. 1998). Osmundson (2002) investigated population dynamics of the 

Colorado River population of Colorado pikeminnow. Two multi-year data collection efforts 

were made: 1991 to 1994, and 1998 to 2000. Annual estimates of whole-river population size 

(all fish > 250 mm TL) averaged 582 during the early study period and 742 during the more 

recent study period, a 27% increase. Annual estimates of adults (> 500 mm TL) averaged 362 

during the early study period and 490 during the recent study period, representing a 35% increase 

in adults. Backwater-netting catch rates supported this trend with an increase in rates between 

1994 and 1998. 
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In both 1999 and 2000, males comprised 51% of the population: females, 49% (Osmundson, 

2002). Average body condition for almost all length-classes of pikeminnow significantly 

declined between the early and recent study periods (Osmundson, 2002). 

Figure 5-Distribution of Colorado Pikeminnow in the Colorado and Gunnison Rivers. 

Colorado Pikeminnow Distribution-Gunnison River 

Although isolated from the Colorado River population by construction of the Redlands Diversion 

Dam in 1917, a small, remnant population of Colorado pikeminnow persisted upstream of the 

dam (Figure 6.1). Burdick (1995) captured five adult Colorado pikeminnow (ranging from 497-

847 mm total length) in the Gunnison River upstream from the dam during an intensive study 

from 1992-1994. Four fish were positively identified while electrofishing but were not captured. 

Two of the captured fish were ripe males found together in a large eddy at RM 33.7 on July 14, 

1993. Of the remaining pikeminnows, one was captured at RM 33.5, one in the flooded mouth 
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of Kannah Creek (RM 18.2) on May 5, 1993 and another at RM 16.7 on the same day. Fish that 

were observed, but not captured were seen at RM 7.7, 30.8 and 32.9 in 1992 and at RM 48.4 in 

October of 1993 (Figure 6). In earlier investigations, Valdez et al. (1982a) captured four adult 

Colorado pikeminnow between RM 26.7 and RM 33 and observed, but did not collect, four more 

between RM 22.1 and 31.4 (Figure 6). The upstream limit of Colorado pikeminnow in the 

Gunnison River is Hartland Diversion Dam, an impassible barrier at RM 59.9, about 57 miles 

upstream from Redlands Diversion Dam (Burdick, 1995). 

In addition, 51 Colorado pikeminnow used the Redlands Fish Passageway from 1996 to 2000 

(Burdick, 2001a). Eight additional Colorado pikeminnow ascended the passageway in 2001 and 

2002. All pikeminnow used the passageway in July and August. There is some movement back 

and forth between the Colorado and Gunnison Rivers: two pikeminnow ascended the 

passageway in 1997, were recaptured in 1998. In addition, one other Colorado pikeminnow that 

ascended the passageway in 1997 was recaptured in 1998 from the Colorado River upstream of 

its confluence with the Gunnison River (Burdick, 2000). It is not know when these fish moved 

back downstream over the Redlands Diversion Dam or how many other fish have returned to the 

Colorado River and have not been recaptured. 

Colorado pikeminnow movements in the Gunnison River were monitored during 1993 and 1994 

(Burdick, 1995). Seven adult Colorado pikeminnow were implanted with radio transmitters. 

The radio-tagged fish used most of the Gunnison River between Redlands and Hartland 

Diversion Dams and one pikeminnow moved back downstream of the Redlands Diversion Dam 

after 78 days. Forty-eight percent of the radio contacts were made between RM 30—40.9, and 

thirty-two percent were made between RM 15—29. Colorado pikeminnow congregated in a 

short reach between RM 30—33 during the estimated spawning period in 1993, with four fish 

between RM 32—33. The reach contained numerous riffles with cobble and gravel substrates 

similar to reaches in other rivers identified as Colorado pikeminnow spawning areas (Lamarra et 

al., 1985; Harvey et al., 1993; Miller and Ptacek, 2000). Occurrence of a congregation at the 

same location for 2 consecutive years during the estimated spawning period suggests that 

Colorado pikeminnow were spawning there (McAda, 2000). 

Larval Colorado pikeminnow have also been collected from the Gunnison River in 1995 and 

1996 (Anderson, 1999), but downstream locations do not help locate specific spawning sites 

because the larvae may have drifted downstream for an unknown distance. 

Colorado Pikeminnow Population Augmentation 

The Recovery Program has identified Colorado Pikeminnow augmentation as a third priority 

behind razorback sucker and bonytail (Nesler et al., 2003). The integrated stocking plan for the 

Colorado River is presented in Table 2 (Nesler et al., 2003). 
16

Figure 6-Gunnison River Colorado Pikeminnow Distribution 

Table 2. Integrated stocking plan for Colorado pikeminnow, third priority species. 

Priority by State and 

River Reaches 

Fish age and 

Size (mm TL) Season Stocked1

Numbers of fish 

stocked per year 

Number of 

years stocked 

Colorado: 

Colorado River: 

Rifle to DeBeque Canyon 

Age 3+ 

150 

1o Fall 

2o Spring-Summer

1,1252 6 

Gunnison River: 

Hartland to Redlands dams 

Age 3+ 

150 

1o Fall 

2o Spring-Summer 

1,1252 6 

1

 1o refers to the primary season; 2o refers to secondary season to cull fish and allow smaller 

individuals to achieve stocking size by the next fall. 

2

 Represents one population in the Upper Colorado and Gunnison rivers. 

Colorado Pikeminnow Habitat Use 

Adult and Sub-Adults—Adult Colorado pikeminnow use a variety of habitats, but exhibit 

preferences for specific habitats during different periods of the year (Tyus and McAda, 1984; 

Osmundson et al., 1995). In the Colorado River near Grand Junction, pools and slow runs (<2.0 

ft/sec) accounted for 77 to 95% of all habitats used by Colorado pikeminnow from November 

through February (Osmundson et al., 1995). More than 74% of all observations during this 
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17

period had mid-column velocities <1.0 ft/sec. Eddies and backwaters were the only other 

habitats used by Colorado pikeminnow in the winter. 

During April—June, river discharge and velocities increased and Colorado pikeminnow sought 

off-channel habitats with reduced water velocities and warmer water temperatures that the main 

river channel (Osmundson et al., 1995). In the Colorado River, Osmundson et al. (1995) found 

that backwaters and flooded gravel pits (combined) comprised 45% of radio tagged Colorado 

pikeminnow locations in April, 49% in May, and 47% in June. These quiet, warm water areas 

allow Colorado pikeminnow to minimize energy expenditures and begin somatic growth or 

gonad maturation sooner than would be possible if they were unable to escape swift, cold water 

of the main river channel (Valdez and Wick, 1983). Other habitats such as eddies and shorelines 

were also used to a lesser degree (Osmundson et al., 1995). Use of main-channel habitats 

increased at summer base flows with slow and fast runs accounting for 49 to 52% of habitats 

selected during July—September (Osmundson et al., 1995). Eddies were used 9 to 16% , pools 

13 to 16%, and riffles 3 to 10% of the time. 

Osmundson and Kaeding (1991) determined that radio-tagged Colorado pikeminnow preferred 

river segments with complex channels (i.e. areas with islands, backwaters, and side channels) 

over simple channels with no side channels or islands. These braided areas provide a greater 

diversity of habitats for Colorado pikeminnow to exploit for resting or foraging and were 

preferred during all seasons. 

Young-of-Year and Yearlings—Small Colorado pikeminnow are highly dependent upon 

backwaters or shallow embayments for nursery habitat (Tyus and Haines 1991; Trammel and 

Chart, 1999a,b). Archer et al. (1985) concentrated sampling efforts on backwaters in the 

Colorado River. More than 98% of the small Colorado pikeminnow collected were found in 

backwaters. Although backwaters are preferred habitat, young Colorado pikeminnow move 

between backwaters and the main channel in response to environmental variables, including 

changes in water temperatures (McAda and Tyus, 1984; Tyus 1991). Trammel and Chart 

(1999b) divided backwaters into six categories, but two backwater types were found in greatest 

abundance in the lower Colorado River—scour channels and migrating sand waves. Scour 

channels are formed by the erosion of small channels behind large sandbars during spring runoff 

and are revealed by receding water levels and typically deep and permanent. Migrating sand 

wave backwaters are formed by the movement of migrating sand waves adjacent to sandbars and 

are relatively shallow and ephemeral. Density of Colorado pikeminnow was highest in scour 

channels and Colorado pikeminnow exhibited a significant preference for scour channels 

(Trammel and Chart, 1991a,b). Winter habitat use by YOY Colorado pikeminnow has not been 

studied. 

Colorado Pikeminnow Reproduction 

Colorado pikeminnow spawn as spring flows decrease and water temperatures increase (Haynes 

et al., 1984; Nesler et al., 1988; Tyus 1990, 1991; McAda and Kaeding, 1991; Bestgen et al. 
18

1998; Anderson, 1999; Trammel and Chart, 1999a,b). In the Colorado River, Colorado 

pikeminnow do not migrate to the extent that they do in the Green River, but migration occurs 

with movement beginning in response to declining runoff and increasing water temperature 

(McAda and Kaeding, 1991). Although some spawning may occur at cooler temperatures, most 

spawning in the Colorado, Green and Yampa rivers occurs at water temperatures between 18—

22 o

C (McAda and Kaeding, 1991; Tyus, 1991, Bestgen et al., 1998; Anderson, 1999, Trammel 

and Chart, 1999a,b). 

Specific spawning sites in the Colorado River are not as well documented as those in the Green 

River sub-basin, although successful spawning occurs every year (Anderson, 1999; McAda and 

Ryel, 1999; Trammel and Chart, 1999a). McAda and Kaeding (1991) concluded that spawning 

in the Gunnison River is generally done by smaller groups and in more locations than Green 

River sub-basin. McAda and Kaeding(1991) reported a presumed spawning aggregation of 

radio-tagged Colorado pikeminnow upstream from the mouth of the Gunnison River, but the 

aggregation was not repeated in subsequent years. Recent efforts have identified five more 

possible spawning sites based on aggregation of Colorado pikeminnow during the presumed 

spawning season (Figure 7) (McAda, 2000). 

Aggregations of pikeminnow at one of the sites downstream of the mouth of the Gunnison River 

were documented in 3 different years. A total of 18 fish were collected from a pool-rifle 

complex in 1994 during the spawning period (D. Osmundson, unpublished data). Ten of these 

fish were ripe males and five others appeared to be females, but no eggs were emitted (sex of 

three other could not be determined). The area was sampled again during the presumed 

spawning period in 1998 and 12 fish were collected, including 7 ripe males and 4 apparent 

females (D. Osmundson, unpublished data). About 25 additional Colorado pikeminnow were 

observed during electrofishing, but could not be captured by the sampling crew. In 1999, nine 

Colorado pikeminnow were captured at this site, including five ripe males and one ripe female 

(gentle pressure extruded eggs when the fish was captured and it was spawned in the hatchery 

later that day without hormone injections [McAda, 2000]). 

Colorado pikeminnow are broadcast spawners that deposit their eggs on cobble substrates in 

riffles and runs (Tyus, 1991). Lamarra et al. (1985) described a known spawning site on the 

Yampa River as being composed of cobble substrate with large interstitial spaces. Hamman 

(1981) documented that Colorado pikeminnow embryos adhered to clean cobble substrate in 

hatchery raceways, so it is likely that a similar process occurs in rivers. After deposition and 

fertilization, the embryos incubate in the cobble for 4-7 days depending on water temperature 

(Hamman, 1981; Marsh, 1985; Bestgen and Williams, 1994). The larvae remain in the gravel for 

another 6-7 days after hatching before emerging from the substrate and becoming entrained in 

the river current (Bestgen et al., 1998). Colorado pikeminnow larvae may drift downstream for 

many miles before settling in low-gradient reaches with abundant backwaters and other quietwater habitats (Tyus and Haines, 1991, Bestgen et al., 1998; Anderson, 1999; Trammell and 

Chart, 1999a). 
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19

Figure 7-Potential Colorado Pikeminnow Spawning Sites in the Colorado and Gunnison Rivers. 

RAZORBACK SUCKER 

The razorback sucker is a large catostomid, endemic to the Colorado River Basin of the western 

United States (Minckley, 1973). The species belongs to a monotypic genus that is distinguished 

by a prominent dorsal keel that rises immediately posterior to the occiput (Minckley, 1973). 

Large individuals may reach a meter in length and weights of 5 or 6 kg (Minckley, 1973), but 

most individuals captured in the upper basin are less than 650 mm long and weigh less than 3 kg 

(McAda and Wydoski, 1980; Tyus, 1987; Tyus and Karp, 1990). It is long-lived and individuals 

may exceed 40 years of age (McCarthy and Minckley, 1987). The historic distribution of 

razorback sucker has been reduced by 75% (Minckley et al., 1991) and its extremely low 

abundance within remaining habitat caused it to be listed as endangered under the Endangered 

Species Act of 1973, as amended (USFWS 1991). 

Razorback Sucker Distribution-Colorado River 

In the Colorado River upstream of Lake Powell, most razorback suckers have been captured in 

the Grand Valley (Loma to Palisade) near the confluence of the Gunnison and Colorado rivers 

(Figure 8). However, their abundance has decreased to the point that they were only 
20

infrequently captured there. During intensive efforts that were specifically targeted at known 

concentration areas of razorback sucker, Kidd (1977) and McAda and Wydoski (1980) captured 

a combined total of 54 razorback suckers in 1974 and 204 in 1975 from two gravel-pit ponds 

connected to the Colorado River near Grand Junction. These numbers reflect the combined total 

of independent collections, but probably include some recaptures of the same fish since sampling 

was done in the same area and Kidd (1977) did not mark fish before release. All of these fish 

exhibited signs of old age (i.e. large size, missing eyes, heavy scarring) (McAda, 2000). The 

high numbers of razorback suckers captured in 1975 were not repeated in subsequent years 

(summarized by Osmundson and Kaeding, 1991). The highest number captured in later years 

was 30 fish that were collected in 1982 from the same gravel-pit pond sampled by Kidd (1977) 

and McAda and Wydoski (1980). Only 11 razorback suckers have been collected from the 

Grand Valley since 1990 despite intensive sampling in some years (Osmundson and Kaeding, 

1991; McAda, 2000). All of these fish have been removed from the river to support propagation 

activities for the Recovery Program (McAda, 2000). 

Although most razorbacks have been collected from the Grand Valley, they have also been 

collected both up and downstream of the area. Kidd (1997) reported 22 razorbacks from the 

Colorado River near DeBeque (RM 209.7) in 1974-1975. No razorbacks have been collected 

from that reach since then (Valdez et al., 1982; Burdick, 1992). Burdick (1992) captured one 

razorback sucker from a gravel-pit pond along the river at RM 243.8 and discovered a small 

population in another gravel-pit pond at RM 204.5. About 75 razorback suckers were captured 

from the second pond, but DNA analysis revealed that they were siblings. They were probably 

offspring from two or three razorback suckers trapped in the pond during the high water year of 

1983 or 1984. Three razorbacks were incorporated into the propagation program, but their close 

relationship precluded extensive use in the brood stock program. Forty-five razorback suckers 

stocked in the Gunnison River as part of an experimental stocking; six of those fish were 

confirmed alive at the end of the 2-year study (Burdick and Bonar 1997). 

Few razorback sucker have been captured downstream from the Grand Valley, between Loma 

and Lake Powell. Taba et al. (1965) captured eight juveniles in backwaters of the Colorado 

River downstream of Moab, Utah. One adult was captured near Salt Wash (RM 144.2 in 1988 

(McAda et al. 1994). Further downstream, Valdez et al. (1982) captured two razorback suckers 

within 2 miles of the confluence with the Green and Valdez (1990) captured one more in the 

same area. 

Razorback Sucker Distribution-Gunnison River 

Anecdotal accounts indicate that razorback sucker were common in the Gunnison River near 

Delta in the early and middle portions of the 20th Century (Kidd, 1997; Quartrone, 1993). 

Razorback suckers in the Gunnison River recorded from knowledgeable collectors are rare. Two 

specimens from the 1940s are in the University of Michigan Museum of Zoology (reported by 

Wiltzius, 1978). Wiltzius (1978) captured one razorback sucker near Delta in 1975 and Holden 

et al. (1981) captured three razorbacks in the same general area in 1981 (Figure 6.4). 
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21

Figure 8-Razorback Sucker Distribution in the Colorado and Gunnison Rivers. 

Extensive sampling by Valdez et al. (1982a) and Burdick (1995) failed to capture any razorback 

suckers from the Gunnison River. Sampling efforts in 2002 collected the first larval razorback 

suckers at two locations on the Gunnison River at a site near Roubideau Creek and a site near 

Whitewater (Figure 9) (C. McAda, unpublished data). These were the first collection of larval 

razorback suckers from the Colorado or Gunnison rivers. In addition, Taba et al. (1965) 

collected the only record of juvenile razorback sucker from the Colorado or Gunnison rivers. 

In 2001 and 2002, six razorback suckers ascended the Redlands fish passageway (B. Burdick, 

unpublished data). The fish passageway was constructed in 1996, however, razorback suckers 

did not begin using the passageway until 2001. 

 

Razorback Sucker Population Augmentation 
22

Although razorback sucker populations have dramatically declined in abundance in recent years, 

the Recovery Program considers the Colorado and Gunnison rivers to be suitable habitat for 

razorback suckers and has begun a reintroduction program to restore populations in the two 

rivers (Burdick, 1992). The Recovery Program developed a broodstock to supplement razorback 

sucker populations in the Colorado and Gunnison Rivers. The Recovery Program in 1996 

initiated a five-year stocking program with the stocking of 7,700 young razorback suckers into 

the Gunnison River near Delta, Colorado (Burdick, 1999). The stocking program has continued 

with the fish stocking of 18,423 juvenile, sub-adult, and adult razorback sucker in the Gunnison 

River and 31,531 juvenile, sub-adult, and adult razorback sucker in the Upper Colorado River 

between April 1994 and October 2001 (Burdick, 2001b). Table 3 presents the sizes, number and 

locations of razorback stocking from 1996—2001 (Burdick, 2001b). The goal of the stocking 

plan is to establish a self-sustaining population of 600 individuals in the 57 miles of usable 

habitat between Harland and Redlands diversion dams. 

Figure 9-Larval and Junvenile Razorback Sucker Collections from the Colorado and Gunnison Rivers. 

 

The Recovery Program also approved a stocking plan by the Colorado Division of Wildlife 

(CDOW) (Nesler, 1998) for the Colorado and Gunnison rivers that includes and expands on 

Burdick’s (1992) plan. The goal of CDOW’s plan is to establish populations of 475 razorbacks 
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per mile in suitable habitat within Colorado. An equivalent plan has been developed for the 

Colorado River within Utah (Hudson et al., 1999) which recommends a population of about 

3,190 or an average of about 30 fish per mile in the section of river razorback suckers are 

expected to inhabit. An integrated stocking plan for Colorado and Utah was developed in 2002 

to address inconsistencies between the states stocking plans (Nesler et al., 2003). Table 4 on the 

follow page presents priority by State and river reaches as well as fish size, seasons to stock, 

number of fish per year, and number of years to stock razorback sucker. 

Burdick (2001b) reported that 235 razorback sucker stocked in the Gunnison and Colorado river 

were either captured (226) from sampling or were found dead (9) during other research sampling 

efforts. This represented about 0.5% of all razorback suckers stocked prior to 2002 (50,254) An 

additional 93 razorback sucker were found dead on the trash grates at the Redlands fish 

passageway in 1999 and 2001 (Burdick, 2001b). 

Table 3. Recovery Program razorback sucker stocked in the Gunnison and Colorado rivers 1996—2001. 

Year Stocking Location Mean Size of Fish 

Actual Number of Fish 

Stocked 

Prior to 1996 Gunnison River 

Colorado River 

18”-21” 

18”-21” 

25 

20 

1996 Gunnison River near Delta 8” 316 

1997 Gunnison River near Delta 8” 

12” 

3,732 

282 

1998 Gunnison River near Delta 12” 608 

1999 Gunnison River near Delta 8” 

12” 

2,742 

30 

1999 Colorado River near Parachute 8” 3,498 

2000 Gunnison River near Delta 8” 6,587 

2000 Colorado River near Parachute and 

Price Stubb Diversion Dam to the 

confluence with the Gunnison River 

8” 25,859 

2001 Gunnison River near Delta 8” 4,101 

2001 Colorado River near Parachute and 

Price Stubb Diversion Dam to the 

confluence with the Gunnison River 

8” 2,154 
24

Table 4. Integrated stocking plan for razorback sucker, first priority species. 

Priority by State and 

River Reaches 

Fish age and 

Size (mm TL) Season Stocked1

Numbers of fish 

stocked per year 

Number of 

years stocked 

Colorado 

1C: Colorado River: 

Rifle to DeBeque Canyon 

Age 2+ 

300 

1o Fall 

2o

 Spring-Summer

3,3102 6 

2C: Gunnison River: 

Hartland to Redlands Dams 

Age 2+ 

300 

1o Fall 

2o

 Spring-Summer 

3,3102

 6 

3C: Colorado River: 

Palisade to Stateline 

Age 2+ 

300 

1o Fall 

2o Spring-Summer 

3,3102 6 

Utah 

1U: Middle Green River: 

(RM 302-249) 

Age 2+ 

300 

1o Fall 

2o

 Spring-Summer 

9,930 6 

2U: Lower Green River: 

(RM 120-249) 

Age 2+ 

300 

1o Fall 

2o

 Spring-Summer 

9,9303 6 

1

 1o refers to the primary season; 2o refers to secondary season to cull fish and allow smaller 

individuals to achieve stocking size by the next fall. 

2

 Represents one population in the Upper Colorado and Gunnison rivers. 

3

 Represents an additional population in case of catastrophic event. 

 Razorback Sucker Habitat Use 

Adults and Sub-adult—Because few razorback suckers remain in the Colorado River, little 

habitat use data are available. Early collections by Kidd (1977) and McAda and Wydoski (1980) 

concentrated in gravel-pit ponds connected to the river. The most heavily used pond was in 

Walker State Wildlife Area (near Grand Junction, Colorado) where razorback sucker were 

collected year-round even though there was access to the Colorado River at all times. This site 

was highly altered by high spring run-off in 1983 and 1984, and razorback sucker use was 

reduced. Osmundson and Kaeding (1989) monitored radio tagged razorback sucker in the 

Colorado River and found in the river, pools and slow runs were the most commonly used 

habitats on a year-round basis, with highest use occurring from early autumn through late winter. 

Backwaters were also used year round, but were most heavily used during spring runoff when 

use of flooded gravel-pit ponds was also high. The greatest variety of habitats were used in 

summer when eddies, riffles, fast runs, and shorelines were occupied; however, slow runs were 

still the most heavily used habitats during that period. Burdick and Bonar (1997) also monitored 

radio-tagged razorback sucker habitat use from fish stocked into the Colorado and Gunnison 

rivers after rearing in riverside gravel-pit ponds. These fish primarily used the main river 

channel (47%), backwaters (23%), and eddy/pools (16%). Fish movements were monitored 

from March—October, however the data was not partitioned by season. 

Larvae and Juveniles—Prior to 2002, no razorback sucker larvae had been collected for the 

Colorado or Gunnison rivers. In 2002, razorback sucker larvae were collect from the Gunnison 

River. Larval razorback sucker were collect downstream of the mouth of Roubideau Creek and 

downstream of Whitewater, Colorado providing evidence that stocked razorback sucker have 
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25

successful spawned in the Gunnison River. Habitats were consistence with those reported by 

Muth et al. (1998) from the middle Green River where 95% of razorback sucker larvae were 

collected from the flood mouths of tributaries or other floodplain-type habitats. It is presumed 

that swim up larvae emerge from the gravel and are carried by the rising river into floodplain 

habitats where they remain during the runoff period (McAda, 2000). 

The only juvenile razorback suckers reported from the Colorado River were captured by Taba et 

al. (1965), who found eight juveniles (90-115 mm TL) in a “quiet backwater area” of the river 

between Moab and Dead Horse Point. This observation was consistent with juvenile razorback 

sucker collected from backwater habitats on the Green River (Modde, 1996). 

Razorback Sucker Reproduction 

Because of the limited number of razorback suckers found in the upper Colorado River, most 

information comes from other parts of the basin. Ripe female razorback sucker have been found 

in Lake Mohave from December through early June (Minckley et al. 1991), but most spawning 

occurs in January—April (Minckley, 1983; Langhorst and Marsh, 1986; Mueller, 1989). Based 

upon capture of ripe fish and subsequent capture of larvae, riverine razorback suckers in the 

upper basin spawn in spring during increasing and peak snow-melt flows (McAda and Wydoski, 

1980; Tyus, 1987; Tyus and Karp, 1990; Muth et al., 1998; Modde and Irving, 1998). 

Osmundson and Kaeding (1991) summarized data collected from the Colorado River near Grand 

Junction and reported that 42 of 157 razorback suckers captured were in spawning condition 

when handled. Of the 42 ripe fish, 40 (95%) were captured between May 24 and June 17. 

Riverine razorback suckers spawn in riffles or shallow runs over gravel or cobble bars (McAda 

and Wydoski, 1980; Tyus, 1987; Tyus and Karp, 1990). Water depths and water velocities vary, 

but are generally relatively shallow (<1 m) and swift (>1 ft/s). In the upper Colorado River 

basin, most ripe fish have been captured from main-channel habitats, but a few were found in 

floodplain habitats (Tyus and Karp, 1990.). In most cases, floodplain habitats were near known 

spawning bars and the fish were probably staging in preparation for spawning (Tyus and Karp, 

1990). McAda and Wydoski (1980) captured two ripe females with a single tremmel net along a 

shoreline with gravel and cobble substrate at Walker State Wildlife Area. Also, 38 of the 42 

razorbacks sucker in spawning condition collected in the Grand Valley during 1974—1991 were 

found in flooded gravel pits (Osmundson and Kaeding, 1991). 

No specific spawning sites have been identified in the Colorado, but the presence of ripe adults 

and presence of mid-channel cobble bars similar to those used in the Yampa and middle Green 

rivers suggests that most spawning in the Colorado River occurred near Grand Junction, 

Colorado (McAda, 2000). The collection of razorback sucker larvae at two locations on the 

Gunnison River (C. McAda, unpublished data), confirms that suitable spawning habitat occurs in 

the Gunnison River, however, no spawning locations have been identified. 

In rivers, razorback sucker larvae emerge from the gravel after swim up and are entrained in the 

current, which carries many of the young fish into floodplains, backwaters, flooded tributary 
26

mouths or other quiet-water habitats for rearing (Tyus and Karp, 1990). Timing of spawning (at 

or approaching the peak of runoff) ensures that these habitats are available to the larvae when 

they emerge from the substrate. Floodplains, backwaters, and other quiet-water areas are the 

most productive habitats of the river (Wydoski and Wick, 1998) and provide important nursery 

habitat for young razorback suckers during the first few months of their lives (Tyus, 1987; Tyus 

and Karp, 1980; Modde, 1996, 1997;Wydoski and Wick, 1998; Muth et al., 1998). These 

habitats are temporary and, with the exception of main channel backwaters, usually do not last 

the growing season. Reduced spring flows caused by water development, and construction of 

dikes and levees reduced the availability of flooded bottomlands (McAda, 2000). 

 

Humpback Chub and Bonytail 

The humpback chub and bonytail are mid-sized cyprinid endemic to the Colorado River Basin 

(Minckley 1973). Both species closely related to the roundtail chub (Gila robusta). 

Humpback chub are currently found in discrete populations, within canyon-bound reaches or 

other areas of similar habitat (Valdez and Clemmer, 1982). Bonytail is the most imperiled of the 

four endangered fishes (Maddux et al., 1993) and it distribution in recent years is limited to 

scattered individuals. Most recently collected individuals were from reservoirs in the lower 

basin where remnant populations remain (Figure 10). One individual humpback chub was found 

during an intensive survey of the Gunnison River from Delta, Colorado to its mouth (Burdick, 

1995). It was captured in a deep eddy-pool complex within a canyon-bound reach at RM 22.0 

and is the only record of a humpback chub from the Gunnison River. The Black Canyon of the 

Gunnison contains habitat similar to that of other canyon-bound areas where humpback chubs 

are currently found. It is possible that they were eliminated from the Black Canyon after water 

temperature was reduced by Blue Mesa Reservoir, but only Gila spp. Reported during preimpoundment surveys were roundtail chub (summarized by Wiltzius, 1978). The humpback 

chub and bonytail, except for the one humpback chub record as noted, do not occur within the 

Gunnison River are not discussed in further detail. Because all four of the endangered fish 

evolved together in the Colorado River ecosystem and flow recommendations based on habitat 

requirements of the more common species and basic river restoration principals (Stanford et al., 

1996) should also benefit humpback chub and bonytail (McAda, 2000). The Recovery Program 

has plans to stock bonytail in the Colorado River from Palisade to Loma including the its 

confluence with the Gunnison River as presented in the next section. 

Bonytail Population Augmentation 

Because of its extreme rarity, the Recovery Program began a reintroduction program in 1997 and 

has stocked about 35,000 bonytail into the Colorado River near Moab to reestablish populations 

(McAda, 2000). Nesler et al. (2003) in the Colorado/Utah integrated stocking plan, identified 
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Figure 10-Distribution of Humpback Chub and Bonytail in the Colorado and Gunnison Rivers. 

Table 5. Integrated stocking plan for bonytail, second priority species. 

Priority by State and 

River Reaches 

Fish age and 

Size (mm TL) Season Stocked1

Numbers of fish 

stocked per year 

Number of 

years stocked 

Colorado: 

Colorado River: 

Palisade to Loma 

Age 2+ 

200 

1o Fall 

2o

 Spring-Summer

2,6652 6 

Utah 

Colorado River: 

(RM 110.5) 

Age 2+ 

200 

1o Fall 

2o

 Spring-Summer 

2.6652 6 

1

 1o refers to the primary season; 2o refers to secondary season to cull fish and allow smaller 

individuals to achieve stocking size by the next fall. 

2 Represents one population in the Upper Colorado River. 
28

bonytail stocking in the Colorado River between Palisade and Loma as a secondary priority 

species behind razorback sucker. The integrated stocking plan for the Colorado River is as 

follows in Table (Nesler et al., 2003). 

EFFECTS ON ENDANGERED COLORADO RIVER FISHES 

Construction, operation, and maintenance of the Redlands fish screen is predicted to be 

beneficial to the Colorado pikeminnow, razorback sucker, and bonytail. The Redlands Power 

Canal is currently unscreened and the fish screen will reduce the potential for incidental take in 

the canal, laterals, ditches, hydraulic pumps, and generating turbines. The fish screen is designed 

to return adult and sub adult fish to the Gunnison River. Larval fish and eggs may still become 

entrained and in the canal downstream of the fish screen resulting in incidental take. In addition, 

there is potential for adult, sub-adult, and larval fish to become impinged on the fish screen, 

stranded in the fish return pipe or entrained when the fish screen is bypassed, resulting in death 

or injury. The fish screen has been designed with adequate mesh size and sweeping velocities to 

minimize the potential for take. However, incidental take may occur. Therefore, the proposed 

Redlands fish screen project is predicted to may affect, likely to adversely affect, the Colorado 

pikeminnow, razorback sucker, and bonytail. 

The proposed fish screen is predicted to have no effect on humpback chub. There is one isolated 

record of humpback chub collected upstream of the Redlands Diversion Dam. This is thought to 

be a remnant from prior to construction of the Aspinall Unit (McAda, 2000). The State of 

Colorado does not plan to augment the humpback chub populations and the closest population in 

Westwater Canyon is a considerable distance downstream in the Colorado River and humpback 

chub movement upstream to the Redlands Diversion Dam and fish passage is not predicted. 

RWPC operations would continue reduced flows in the lower 2.3 miles of the Gunnison River 

and deplete water from the Gunnison River. The continued RWPC operations may affect, likely 

to adversely affect, the Colorado pikeminnow, razorback sucker, bonytail and humpback chub. 

During previous consultations regarding historic depletions, the Service has identified the Upper 

Colorado River Endangered Fishes Recovery Program as the reasonable and prudent alternative 

to avoid jeopardy to the endangered Colorado River fishes. 

BALD EAGLE 

The bald eagle (Haliaeetus leucocephalus) was classified as endangered in 43 of the 48 

contiguous states on February 14, 1978. The species was reclassified threatened by the U.S. Fish 

nd Wildlife Service August 11, 1995 (USFWS, 1995b). 

 

The bald eagle is distinctive by it white head, white tail plumage, dark brown to charcoal black 

wing and body plumage, and massive yellow bill. The bald eagle ranges from 30-43 inches (75-

108 cm) in height and has a wingspan between 7-8 ft. Males often appear darker than females. 
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Females are larger than males. Immature bald eagles (6 months to 2 years old) have a dusky 

head and tail plumage (Peterson, 1990; USBR, 1994). 

Feeding habitats are eclectic, reflecting the opportunistic behavior of large raptors. Prey species 

includes: fishes, ground dwelling scuirids, waterfowl, ungulate carrion and lagomorphs (USBR, 

1994). 

Age of first breeding is commonly assumed to be coincident with acquisition of definitive adult 

plumage. Breeding commonly occurs between ages 6 and 7 years old. Nest building and repair 

occur every year. Both male and females build stick nests used over many years. Nests can be 

as large as 3 m (10 ft.) high and 2.1 m (7 ft.) wide. Alternate nests may be present in the 

breeding area, but pairs usually use one nest until it either falls from the tree or the tree is lost 

(USBR, 1994). 

Egg laying normally occurs in early February to mid-April depending on elevation. Average 

clutch size is two eggs. Incubation averages 31 to 35 days. Eggs hatch in mid-March to midMay and the nesting period lasts 11 to 14 weeks. Both genders incubate, brood and feed young 

but the female performs most of the tasks. Fledglings are dependent on adults for 6 to 10 weeks 

and adults will feed juveniles other than their own (USBR, 1994). 

Bald Eagle Habitat Preference 

Bald eagles occupy riparian or lacustrine habitats almost exclusively during the breeding season, 

but occasionally exploit upland areas for food and roost sites, especially during the winter. Nests 

sites are mostly commonly distributed around the periphery of lakes and reservoirs larger than 80 

acres in size. Nesting also occurs linearly along forested corridors of major rivers, usually within 

1 mile of shore, however cases have been reported of birds nesting as far as 9.3 miles from water 

while exploiting locally abundant prey such as prairie dogs (USBR, 1994). 

Bald Eagle Distribution and Abundance 

The bald eagle is the only species of Haliaeetus occurring in and restricted to North America. 

Historic bald eagle distribution included every state (except Hawaii) and Canadian province and 

portions of northern and eastern Mexico (Brown, 1976). Populations became depressed in the 

1960's from effects of use of the pesticide DDT. 

The Gunnison and Colorado rivers both provide suitable wintering habitat for the bald eagle and 

are considered to be good winter areas. Bald eagle nesting is uncommon. The closest known 

nest site is on the Colorado River near Ruby Canyon approximately 30 miles downstream of its 

confluence with the Gunnison River. Eagles have also attempted to nest at sites near Walter 

Walker and Horsethief Canyon State Wildlife Areas downstream on the Colorado River 

(CDOW, 2003). Bald eagles are known to be seasonal winter residents to the Colorado River 

Wildlife Area located at the confluence of the Gunnison and Colorado rivers approximately 2.3 
30

miles downstream of the project area (Shannon, 2003). These birds have been observed roosting 

in large cottonwood trees on the Colorado River in the fall, winter and early spring. No eagles 

have been observed roosting within the wildlife area along the Gunnison River. 

EFFECTS ON BALD EAGLE 

Roosting and nesting habitat occur within the project area, however no bald eagles nesting has 

been documented. Eagles may use the project area during winter for foraging. Large 

cottonwood trees are found on both sides of the Gunnison River upstream and downstream of the 

diversion dam, however no known winter concentration area occurs within the project area. It is 

estimated that approximately 7 mature cottonwood trees would be removed during construction 

of the fish screen return pipeline. The cottonwood trees lost would be mitigated on-site with a 

planting ratio of 10 cottonwood saplings to 1 mature cottonwood tree removed. Fish screen 

construction would begin prior to the arrival of wintering bald eagles. Bald eagles may avoid 

the project area during construction, however, project effects are predicted to be short-term in 

duration. Continued operation and maintenance of RWPC’s facilities is predicted to have no 

effect on the bald eagle. 

INDIRECT PROJECT AND CUMULATIVE EFFECTS 

The continued operations of RWPC will likely have indirect effect within the project area 

including increased noise levels, impacts to air quality and water quality, increased light levels, 

and land use changes within the project area. 

As part of the Reclamation’s proposed mitigation, endangered Colorado fishes will be preserved 

through actions of the Recovery Program including the continued operations of the Redlands 

Fish Passageway, construction and operation of the Redlands Fish Screen, continued Colorado 

pikeminnow and razorback sucker population augmentation, and re-operation of the Aspinall 

Unit to attempt to meet Gunnison and Colorado River flow recommendations (McAda, 2000) to 

assist in the recovery of the endangered Colorado River fishes. The goal of the proposed 

mitigation is to protect, preserve and enhance endangered Colorado River fish habitats within the 

project area as well as known endangered fish populations upstream and downstream of the 

project area potentially affected by RWPC’s operations. Additionally, Reclamation relies on the 

Recovery Program’s educational and outreach components to educate the public about the 

endangered Colorado River fishes within the proposed project area. 

CONSIDERATION OF FEDERALLY THREATENED AND 

ENDANGERED PLANTS 

At this time, there are no known federally threatened or endangered plants within the proposed 

project area. A total of six habitat types were identified during the biological assessment for this 

project. The primary cover types in the area are: 1) residential and commercial development 

(building, roads, lawns, dams, gravel mines, golf courses, etc.), agricultural, riparian, wetland, 

rivers, and upland habitats. 
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31

CRITICAL HABITAT 

The Colorado and Gunnison rivers and their 100-year flood plains within the project area 

designated as critical habitat for the endangered Colorado River fishes (USFWS, 1994) (Figure 

11). 

. 

Craig

Steamboat Springs

Rifle Glenwood Springs

Fruita Aspen

Grand Junction

Delta

Montrose Gunnison

Ouray

Cortez

Durango

Green River

Colorado River

White River

Yampa River

Gunnison River

Lake Powell

Flaming Gorge

Reservoir

Blue Mesa 

Reservoir

San Juan

River Navajo

Reservoir

Utah

Colorado

Wyoming

Arizona New Mexico

N

W E

S

Upper Colorado and San Juan

River Basin Critical Habitat

Figure 11-Upper Colorado River Basin Endangered Fishes Critical Habitat 

MINIMIZING AND MITIGATING IMPACTS TO THE COLORADO 

RIVER ENDANGERED FISHES 

The Governors of the states of Colorado, Utah, and Wyoming, the Secretary of the Interior, and 

the Western Area Power Administrator established the Upper Colorado River Endangered Fish 

Recovery Program in 1988. The Recovery Program is a cooperative partnership involving public 

and private agencies and interests dedicated to recovering the endangered Colorado River fishes 

while water development proceeds in compliance with Federal and State laws. Recently in 2002, 
32

the Recovery Program participants signed a ten-year extension of the cooperative agreement, 

extending the program through September 30, 2013. 

The Recovery Program, through the implementation of the Recovery Implementation Program 

Recovery Action Plan (RIPRAP), has been the reasonable and prudent alternative to avoid 

jeopardy for Service consultations on 707 water projects depleting approximately 1,719,273 

acre-feet per year in the upper basin. The Service simplified the Section 7 consultation process, 

and waived depletion charges for water projects that deplete less than 100 acre-feet of water per 

year. Through the implementation of the RIPRAP action items within the lower Gunnison River, 

it is reasonable to assume that the continued operations of RWPC will have minimal impact on 

the continued existence of the endangered Colorado River fishes. Incidental take, however may 

occur, and requires Service authorization through Sections 7 and 10 of the Endangered Species 

Act. 

It is Reclamation’s recommendation that the authorized level of incidental take be consistent 

with that issued for consultation under the “15 mile Reach” Programmatic Biological Opinion 

(PBO) (USFWS, 1999). The PBO set the level of incidental take at 1 percent of the current adult 

Colorado pikeminnow population above Westwater Canyon. The PBO also estimated the 

anticipated level of take for razorback sucker to 2 adult fish per year until augmentation efforts 

are successful above the diversion structures. The Service estimated the future incidental take to 

be 1 percent of population. The following activities would be implemented to avoid, minimize, 

and mitigate for the impacts to the endangered Colorado River fishes as a result of the continued 

RWPC operations: 

◄The Recovery Program would continue to fund operation and maintenance of the 

Redlands Fish Passageway to provide Colorado pikeminnow and razorback sucker passage 

upstream of the Redlands Diversion Dam. The Service would continue to operate the fish 

passageway to allow endangered and native fish passage upstream, while removing non-native 

fish species. The fish passageway would continue to be operated each year from April through 

October or at times determined as reasonable by the Service. RWPC, through an executed 

Operating and Maintenance (O&M) Agreement with Reclamation, would perform maintenance 

on the fish passageway, subject to funding from the Recovery Program. 

◄RWPC would assume ownership of the Redlands Fish Passageway from Reclamation 

and allow the Service continued access to the fish passageway for operations. 

◄RWPC would allow Reclamation to design and construct a fish screen in the Redlands 

Power Canal to return canal entrained adult and sub-adult Colorado pikeminnow and razorback 

sucker to the Gunnison River. RWPC will assume ownership of the Redland Fish Screen and 

through an executed O&M agreement, operate and maintain the fish screen with funding 

provided by the Recovery Program. 

◄RWPC would operate the fish screen at all times with exceptions to periods when the 

screen is not functioning properly because of inadequate river flows, icing, or screen fouling. 
H:\Home\700Lib\FishUCRIP\Fish Screens\Final Biological Assessment

33

RWPC would work directly with the Service and Reclamation to promptly address fish screen 

operation and maintenance issues to ensure that incidental take of the endangered Colorado 

River endangered fishes is limited. The Recovery Program would monitor incidental take levels, 

and would assume responsibility of modifying the fish screen as needed in consultation with the 

Service and RWPC. 

◄Reclamation, the Service, Western Area Power Administration, and the National Park 

Service (Federal Agencies of the Recovery Program) would continue to participate in and 

support the Upper Colorado River Recovery Endangered Fishes Recovery Program. 

◄Reclamation would continue to work with the Service to implement Colorado and 

Gunnison River flow recommendations when finalized. 

SUMMARY AND CONCLUSIONS 

The construction, operation and maintenance of the Redlands fish screen is predicted to have no 

effect on the humpback chub and bald eagle. The Redlands fish screen would reduce canal 

entrainment and the potential for incidental take of Colorado pikeminnow, razorback sucker and 

bonytail. Incidental take may still occur, but at a significantly lower level. Therefore, the 

construction, operation and maintenance of the Redlands fish screen is predicted to may affect, 

likely to adversely affect, Colorado pikeminnow, razorback sucker and bonytail. Incidental take 

coverage is needed for the operation of the fish screen. 

RWPC depletions and operations may affect, likely to adversely affect, the Colorado 

pikeminnow, razorback sucker, bonytail and humpback chub. The Upper Colorado River 

Endangered Fishes Recovery Program has served as the reasonable and prudent alternative to 

avoid jeopardy during consultations since 1988 on 707 water projects. 

 
34

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