Native Fish of the Lower Dolores River
Status, Trends, and Recommendations
Dan Kowalski Rick Anderson
Jim White Barry Nehring
Native Fish of the Dolores River
• Native Fish Species
• Current Status and Trends
• Comparisons to Other Rivers
• Native Fish Habitat-Flow Relationship
• Conclusions and Recommendations
– Ann Oliver's Questions
– Non-Native Fish Control
– Lower Dolores Working Group Wild and Scenic
Alternatives
• Discussion
Native Fish Species of the Dolores River
• Colorado Pikeminnow FE, ST
• Bluehead Sucker SS
• Flannelmouth Sucker SS
• Roundtail Chub SSC, SS
• Speckled Dace
• Mottled Sculpin
• Colorado River Cutthroat Trout SSC
• Not Confirmed
– Razorback Sucker FE
– Humpback Chub FE
– Bonytail FE
FE- Federally Endangered
ST- State Threatened
SSC- State Species of Special Concern
SS- BLM Sensitive Species
Native Species Accounts
• Colorado Pikeminnow
– Large predatory fish (70+ inches and 80 lbs)
– Naturally lower density, move great distances
– Habitat generalist but dependent on natural peak flows for
habitat and spawning cues
– Population declines associated with reduced peak flows in
Colorado and Gunnison rivers
• Bluehead Sucker
– Facultative herbivore, forages in riffles for algae, detritus,
occasional invertebrates
– Strongly associated with medi-riffle habitat, dependant on
adequate base flows and quality of riffle habitat
– Currently occupy about 50% of historic habitat
Native Species Accounts
• Flannelmouth Sucker
– Omnivore consumes algae, detritus, invertebrates
– Associated with deep semi-swift run habitat, can withstand
reduced peak flows but limited by base flows and quality
riffle-run habitat
– Currently occupy about 45% of historic habitat
• Roundtail Chub
– Opportunistic predator, aquatic insects major prey
– Habitat generalist more associated with pool habitat,
prefer murky water
– More likely to be limited by food resources than habitat
– Currently occupy about 45% of historic habitat
Flannelmouth Sucker
Roundtail Chub
Bluehead Sucker
Colorado Pikeminnow
Colorado Pikeminnow in the Dolores River
• Pikeminnow documented in the Dolores from 1950’s to 1970’s
as far up river as Paradox Valley and into the lower end of the
San Miguel
• Last sampled in the Dolores in 1992 in Utah and 1973 in CO
• Dolores confluence with the Colorado is an area with
documented aggregations of pre-spawn pikeminnow
• 1992 pikeminnow habitat evaluation concluded the Dolores
potentially contained habitat to support all life stages of CPM
but habitat was severely impacted by low base flows
• Concluded that base flows of 20 to 40 cfs reduced native fish
habitat in the lower 170 miles of the Dolores River through
decreased fish holding areas, dewatered nursery backwaters,
impeded movement, and enhanced sedimentation
Historic Fish Population Sampling
• 1975 Holden and Stalnacker
– 11 species, 4 natives: flannelmouth, bluehead, roundtail,
speckled dace
• USFWS 1982
– 16 species, 4 natives: flannelmouth, bluehead, roundtail,
speckled dace
• Valdez 1992
– 19 species, 6 natives: flannelmouth, bluehead, roundtail,
speckled dace, mottled sculpin, Colorado pikeminnow
– Concluded that native fish numbers and distribution were
similar to 1982 study
Current Status of Fish Populations
Current Fish Populations
2007 Longitudinal Survey
Pyramid
Big Gypsum
Slickrock
Gateway
Flannelmouth
0.4
4.5
2.7
2.2
Bluehead
0.1
0.5
0.2
3.9
Roundtail
0.5
18.6
1.8
0.1
3 Native Spp.
1
23.6
4.7
6.2
Native Fish
Composition
10%
94%
79%
51%
Catch Per Unit Effort (CPUE) in Fish Per Mile
Current Fish Populations
2009 Sampling Below the San Miguel
Species
% Catch
Mean Length
(in.)
CPUE
(fish/mile)
Bluehead Suckers
33
8.5
26.3
Flannelmouth Suckers
33
14.6
26.1
Roundtail Chubs
14
7.1
11.4
Speckled Dace
9
3.4
7.6
Channel Catfish
8
11.1
6.3
Common Carp
2
21.3
1.6
Red Shiner
1
3.0
0.4
Sand Shiner
0
2.8
0.2
Native Fish Population Trends
Fish Population Trends
Metaska to Bradfield Bridge
0
20
40
60
80
100
120
140
160
180
200
1992
1993
1997
1998
1999
2000
2005
Number Sampled
Flannelmouth Suckers
Bluehead suckers were also sampled in low numbers from1992-1997.
Biomass of flannelmouth suckers in 1993 was estimated at 23.1 kg/ha.
Average length of flannelmouths sampled 1992 to 1999 was 415 mm (16 in).
Fish Population Trends
Bradfield Bridge to Dove Creek
Biomass of flannelmouth suckers in 1993 was estimated at 57.9 kg/ha.
Average length of flannelmouths sampled 1993 to 1997 was 445 mm (17.5 in).
0
50
100
150
200
250
300
350
1993
1997
2005
2007
Number Sampled
Flannelmouth
Bluehead
Fish Population Trends
Dove Creek Native Suckers
0
2
4
6
8
10
12
14
16
86
89
91
93
95
97
99
02
04
06
08
Number Sampled
Flannelmouth
Bluehead
Fish Population Trends
Dove Creek to Gateway
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
1990
1991
2007
CPUE (fish/hr)
Flannelmouth
Bluehead
Roundtail
Surveys: 1990, 1991 Valdez, 2007 White and Kowalski
Fish Population Trends
Dove Creek Roundtail Chub
0
20
40
60
80
100
120
140
86
89
91
93
95
97
99
02
04
06
08
Number Sampled
Fish Population Trends Big Gypsum
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
2000
2001
2004
2005
2006
2007
CPUE (fish/Mile)
FMS
BHS
RTC
Total Natives
Native Fish Population Trends
• Native suckers increased in abundance from 1986 to early 1990’s
and then declined in numbers and range
– Today native suckers are almost absent from 53 miles of
previously occupied habitat above Disappointment Creek and
their numbers have declined in the occupied range below
• Large (>400 mm) adult flannelmouth suckers were common in the late
80’s to early 90’s up to Bradfield bridge and biomass was estimated
between 20 and 60 kg/ha
– Presently native fish appear no better or worse than pre-dam
– Colorado pikeminnow has been extirpated from river post-
dam
• Trout fishery below dam has followed similar trends
Comparisons to Other Rivers
(Anderson 2002-2006)
Gunnison (Delta)
Colorado
(Clifton)
Dolores (Big
Gypsum)
Hydrograph Alterations
Reduced Peak,
Good Base
Flows
Reduced
Peak, Good
Base Flows
Reduced Peak,
Reduced Base
Flows
Mean Annual Flow (cfs)
2,564
2,817
284
Slope (%)
0.16
0.2
0.15
Typical Base Flow (cfs)
1000
1000
30
Mean Velocity (m/s)
0.69
0.44
0.28
Mean Width (m)
42
59
21
Width/Depth Ratio
52
77
46
3 Species Biomass (kg/ha)
422
232
0.6*
Native Species
Composition
69%
64%
42%
*Dolores River from dam to Dove Creek supported 20-60 kg/ha native suckers in the
early 1990’s
Dolores and San Miguel River Comparison
Dolores @ Bedrock
San Miguel @
Uravan
Watershed Size (mi
2
)
2,024
1,499
Average Annual Discharge
(af)
227,186*
262,269
Average Annual Discharge
(cfs)
284
347
Native Fish Per Mile
14.2**
45.6
*1985 to present. Pre-dam average annual discharge was 340,526 af
**Average from Big Gyp and Slickrock Canyon data 2007
River Comparisons
• Native fish in the Dolores have a much smaller average size than other
populations and sexually mature at smaller sizes
– FMS usually mature at 4-6 years and 300-400 mm (12-16 in)
– 2006 Sampling above Disappointment found 182 mm (7 in) FMS ripe
with eggs
• Miniaturization could be an adaptation to habitat reductions
Big Gyp 2007
San Miguel 2008
Gunnison 2008
FMS
8.6
14.5
13.6
BHS
7.2
10.2
10.7
RTC
5.7
8.2
9.2
Average Fish Length (in)
0
5
10
15
20
25
10
70
130
190
250
310
370
430
490
550
Number Captured
Length (mm)
San Miguel River 2008
Flannelmouth
Bluehead
0
1
2
3
4
5
6
7
5
45
85
125
165
205
245
285
325
365
405
445
485
525
Number Sampled
Length (mm)
Native Fish Length Frequency Histogram
Big Gypsum 2007
Flannelmouth
Roundtail
Current Native Fish Populations Conclusions
• Native fish have declined significantly in the Dolores in
the last twenty years, one species of native fish is
functionally extinct from the river
• Dolores River above the San Miguel has one of the
poorest native fish population of any large western
Colorado river
– Supports less than 1 kg/ha of native fish compared to 100-400
kg/ha in other rivers and 20-60 kg/ha in Ponderosa Canyon in
the late 1980’s
– Supports much smaller average sized fish, smaller size at
maturity, and poor year class representation
• Dolores below the San Miguel confluence supports the
best populations of native fish in the river
Native Fish Habitat Investigations
Native Fish Habitat Investigations
• CWCB Instream Flow Recommendation
– 78 cfs to the San Miguel Confluence
– R2Cross: 1 dimensional cross section method that focuses on
ecological function of rivers indicated by riffle habitat quality
• PHABSIM Habitat Modeling
– Nehring 1985: 150 cfs below the dam for the trout fishery
– 1D habitat model that is effective in estimating microhabitat
availability and is very useful for coldwater sportfish
• 1992 Pikeminnow Habitat Suitability Study
– Suitable habitat in Dolores but impacted by low flows
– Recommended minimum flows of 50-78 cfs for pikeminnow
• 2D Habitat Modeling for Native Fish
– Anderson 2007
Native Fish Habitat Study 2000-2006
• 2-dimensional habitat modeling used to
model fish habitat availability at the micro and
meso habitat level
• Research grade sonar and total station GPS
was used to survey habitat variables
• Habitat suitability models were developed
with site specific electrofishing samples
– Habitat suitability models were validated and did a
good job of predicting observed fish biomass (r
2
of
0.74-0.90)
Flannelmouth Sucker Habitat Suitability
Modeling
Flannelmouth Sucker Habitat-Flow Relationship
Flannelmouth Sucker Habitat Availability
Bluehead Sucker Biomass-Flow Relationship
Bluehead Sucker Habitat Availability
Summary of Native Fish Flow Study
• Flow of 300 cfs maximizes BHS and FMS habitat in the Dolores
• Concluded that inadequate riffle quantity and quality limited
native fish habitat as well as decreased invertebrate
productivity
– Deep, higher velocity riffles were very rare in the Dolores
at flows < 60 cfs
• Low flows result in too little velocity and depth in the majority
of riffle and run habitats for FMS and BHS
• Poor invertebrate production due to lack of quality riffle
habitat limits food resources for roundtail chub
• 80 cfs (60 cfs with spill) minimum flow recommendation at Big
Gypsum that would protect 12-22% of maximum native fish
habitat
Native Fish Habitat and Non-Native Fish
• Lack of high peak flows have resulted in bank encroachment,
decreased width to depth ratio, and increased pool frequency
– Post dam conditions have altered hydrograph and
sediment dynamics
• Unnatural hydrograph, temperature, and sediment regime
also creates more favorable conditions for non-native fish
– NN fish are a problem in Dolores (smallmouth bass,
catfish) but impacts pale in comparison to habitat issues
– NN fish control efforts are not likely to be effective in the
Dolores because of species present and available access
• Extensive experience with fish control for pike, smallmouth, and
bass in the Yampa and Colorado Rivers
– Improving/maintaining native fish habitat is the key in
discouraging non-native fish expansion (smallmouth bass)
Native Fish Flow Needs
Min Flow Recommendation
Flow (cfs)
Location
Release
Necessary
(cfs)
Volume (af)
% Max
Bluehead
Biomass
CWCB Instream Flow
78
McPhee to
San Miguel
94
68,037
22
Nehring 1985 (Trout)
150
Below
McPhee
150
108,569
33
Anderson 2007 (With Spill)
60
Big Gypsum
72
52,113
12
Anderson 2007 (No Spill)
80
Big Gypsum
96
69,484
22
Current Fish Pool
41
(28 at Gyp)
Below
McPhee
41
29,300
3
Current fish pool is 43% of the MINIMUM flow necessary to protect a barely
viable fishery and protects less than 5% of native fish habitat
Native Fish Flow Needs
• Bad News: Current fish pool does not provide enough habitat for viable native
fish populations
• Good News: Curve is steep, large habitat gains with a little more water
Questions from DRD
• What is known about the status of the 3 natives and the roundtail in particular
in the Dolores River? What about the Four Endangered fish?
• Native fish have declined significantly and are barely viable above the San Miguel
• Endangered fish have been functionally extirpated from the river since the 1980’s
• Is there data on trends? For what time period?
• Good data on trends from 1986-Present, pre-dam data only spot sampling
• What is the strength of the data - how much certainty/uncertainty is
associated?
• Varies with each data set, sampling is generally CPUE population indices or
minimum counts so measures of precision are not possible or necessary
• High amount of certainty about conclusions due to magnitude of decline, current
condition of fish population, and corroboration with habitat modeling studies
• What do we know about the reasons for the trends?
• Lack of habitat due insufficient flow is the reason for native fish declines
Questions from DRD
• What key data gaps exist with respect to native fish?
• Age/growth information, spawning ecology of natives, aquatic
invertebrate data, temperature and nutrient issues, smallmouth bass
age/grown and ecology
• Data gaps are academically interesting but not necessary for management
decisions
• What do we know about the flow needs for the native fish?
• We have excellent information on flow needs of both native and sport
fish, one of the most thoroughly researched subjects with state of the art
techniques
• Given the dam, in your opinion, how can we ensure persistence of these fish
in the Dolores?
Recommendations
• Increased downstream flows should be first priority
– Fish pool should at least be at the 36,500 af identified in
the 1996 EA with ultimate objective of year round
minimum flow of at least 78 cfs
– Current conditions provide less than 43% of the MINIMUM
downstream flow needs and protects less than 4% of
potential native sucker biomass
• Spill management is critical with so little water allocated for
downstream release
– Start spill April 1 and extend for as long as possible with
clock on fish pool off
– With 36,500 af fish pool and a 90 day spill would be 85% of
minimum downstream flow needs and would protect
about 10% BHS biomass
Recommendations
• Alternatives for Wild and Scenic Designations
– Any alternative that does not increase downstream
releases will NOT protect the fish ORV in Dolores
– Status quo produces less than 5% of potential native fish
habitat is only about 43% of necessary minimum flows
• Downstream releases have actually declined and the fish pool has
gotten smaller in the last 15 years, the water situation is getting
worse not improving
• Protecting flows in the San Miguel River is essential for
sustaining viable native fish populations in the Dolores River
– State instream flow protection and/or Wild and Scenic
Designation should be explored to protect San Miguel
River flows
Future Plans
• DOW is compiling all Dolores River native fish data into a
summary report that will include all historical fish sampling
data, current distributions, and population trends
• A range-wide status assessment is also underway to evaluate
historical distributions, current distribution, and make specific
conservation recommendations
– Range-wide Conservation Agreement and strategy for Roundtail Chub,
Bluehead Sucker, and Flannelmouth Sucker
– Signatories include Sate of Colorado, BLM, and BOR
• Further monitoring efforts on the Dolores will not be a
priority for DOW unless conditions for native fish improve
– Spill management has not been favorable for fish sampling conditions
and fish pool water is way too scarce to used for monitoring
Questions and Discussion