Introduction

This report contains ancillary capture data from targeted nonnative fish removal and other efforts throughout the Upper Colorado River Basin. The data was queried from the Species Tagging, Research and Monitoring System (STReaMS) on 2026-01-15. Only physical capture data is included in this report. Due to heterogeneity in sampling protocol across projects, only non-native species data are included in this report. Species summaries are limited to raw capture counts, spatial distributions of captures and length frequency histograms aggregated by river. Information on listed species (Colorado pikeminnow, razorback sucker, humpback chub and bonytail) and non-native species specifically targeted for removal (smallmouth bass, walleye and northern pike) can be found on the Upper Colorado River Recovery Program’s website. For information on non-listed native species contact the Utah Division of Wildlife Resources Utah Natural Heritage Program or Colorado Parks and Wildlife’s Aquatics Data Management System (ADAMAS)


An artistic image featuring native fish in the center surrounded by nonnative fish



Total fish encounters by species recorded in the Upper Colorado River Basin during fieldwork in 2025. Includes all available project data at time of query
Common Name Nativity Number of Encounters
smallmouth bass Targeted Non-native 41927
white sucker Non-native 27021
largemouth bass Non-native 9850
green sunfish Non-native 9658
flannelmouth sucker Native 7582
bluehead sucker Native 7333
black bullhead Non-native 3431
roundtail chub Native 3239
brown trout Non-native 1858
razorback sucker Native 1852
flannelmouth sucker x white sucker Native / Non-native x 1327
mountain whitefish Native 1091
northern pike Targeted Non-native 1070
gizzard shad Non-native 930
channel catfish Non-native 863
bluegill Non-native 760
carp Non-native 750
bluehead sucker x white sucker Native / Non-native x 664
black crappie Non-native 503
Colorado pikeminnow Native 344
red shiner Non-native 341
sand shiner Non-native 335
walleye Targeted Non-native 279
speckled dace Native 278
creek chub Non-native 223
fathead minnow Non-native 152
bonytail Native 136
rainbow trout Non-native 122
bluehead sucker x flannelmouth sucker Native x 98
longnose sucker Non-native 83
American bullfrog NA 37
flannelmouth sucker x razorback sucker Native x 34
mottled sculpin Native 24
brook stickleback Non-native 19
grass carp Non-native 15
redside shiner Non-native 12
humpback chub Native 9
cutthroat trout Native 6
bluehead sucker x longnose sucker Native / Non-native x 5
unidentified Unknown 5
yellow bullhead Non-native 5
Colorado River cutthroat trout Native 4
Unidentified crayfish NA 4
bluegill x green sunfish Non-native x 4
burbot Non-native 2
cutthroat trout x rainbow trout Native / Non-native x 2
native chub not identified to species Unknown 2
striped bass Non-native 2
Goldfish Non-native 1
flannelmouth sucker x longnose sucker Native / Non-native x 1
yellow perch Non-native 1


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Disclaimer: These data are for general informational purposes, they are not comparable across species, years or geography!!! Use with caution


Nonnative Fish

The upper Colorado River basin has had over 50 nonnative fish species introduced, some of which are predatory and contribute to the decline of native fish throughout the river. Data from the more notable nonnative species which do not have focused projects are summarized below.

Black Crappie


Hydrologic Area Sampling Date Range Sampling Mile Range Number of Captures
Green River Mar 12 - Sep 25 120 - 381 78
Colorado River Mar 31 - Nov 06 0 - 242.9 65
Yampa River Mar 30 - Jun 30 0 - 194.1 45
White River May 20 - Jun 19 29 - 104.3 25
Gunnison River Apr 07 - Oct 20 0 - 57.1 1


Heatmap displaying the spatial distribution of black crappie captures within major rivers of the Upper Colorado River Basin


This chart has title 'Length Frequency for Black Crappie by River'. The chart is comprised of 5 panels containing sub-charts, arranged horizontally. The panels represent different values of nm_rvr. Each sub-chart has x-axis 'Total Length' with labels 100, 200 and 300. Each sub-chart has y-axis 'Total Fish Encountered' with labels 0, 10 and 20. Panel 1 represents data for nm_rvr = Colorado River. Panel 1 is a bar chart with 13 vertical bars. It has colour set to black. Panel 2 represents data for nm_rvr = Green River. Panel 2 is a bar chart with 13 vertical bars. It has colour set to black. Panel 3 represents data for nm_rvr = Gunnison River. Panel 3 is a bar chart with 13 vertical bars. It has colour set to black. Panel 4 represents data for nm_rvr = White River. Panel 4 is a bar chart with 13 vertical bars. It has colour set to black. Panel 5 represents data for nm_rvr = Yampa River. Panel 5 is a bar chart with 13 vertical bars. It has colour set to black.



Largemouth Bass


Hydrologic Area Sampling Date Range Sampling Mile Range Number of Captures
Colorado River Mar 31 - Nov 06 0 - 242.9 8051
Gunnison River Apr 07 - Oct 20 0 - 57.1 349


Heatmap displaying the spatial distribution of largemouth bass captures within major rivers of the Upper Colorado River Basin


This chart has title 'Length Frequency for Largemouth Bass by River'. The chart is comprised of 2 panels containing sub-charts, arranged horizontally. The panels represent different values of nm_rvr. Each sub-chart has x-axis 'Total Length' with labels 0, 100, 200, 300 and 400. Each sub-chart has y-axis 'Total Fish Encountered' with labels 0, 250, 500 and 750. Panel 1 represents data for nm_rvr = Colorado River. Panel 1 is a bar chart with 23 vertical bars. It has colour set to black. Panel 2 represents data for nm_rvr = Gunnison River. Panel 2 is a bar chart with 23 vertical bars. It has colour set to black.



Striped Bass


Hydrologic Area Sampling Date Range Sampling Mile Range Number of Captures
Colorado River Mar 31 - Nov 06 0 - 242.9 2


Heatmap displaying the spatial distribution of striped bass captures within major rivers of the Upper Colorado River Basin




Burbot


Hydrologic Area Sampling Date Range Sampling Mile Range Number of Captures
Green River Mar 12 - Sep 25 120 - 381 2


Heatmap displaying the spatial distribution of burbot captures within major rivers of the Upper Colorado River Basin




Gizzard Shad


Hydrologic Area Sampling Date Range Sampling Mile Range Number of Captures
Colorado River Mar 31 - Nov 06 0 - 242.9 912
Gunnison River Apr 07 - Oct 20 0 - 57.1 17


Heatmap displaying the spatial distribution of gizzard shad captures within major rivers of the Upper Colorado River Basin


This chart has title 'Length Frequency for Gizzard Shad by River'. The chart is comprised of 2 panels containing sub-charts, arranged horizontally. The panels represent different values of nm_rvr. Each sub-chart has x-axis 'Total Length' with labels 100, 200, 300, 400 and 500. Each sub-chart has y-axis 'Total Fish Encountered' with labels 0, 25, 50 and 75. Panel 1 represents data for nm_rvr = Colorado River. Panel 1 is a bar chart with 23 vertical bars. It has colour set to black. Panel 2 represents data for nm_rvr = Gunnison River. Panel 2 is a bar chart with 23 vertical bars. It has colour set to black.



Bluegill


Hydrologic Area Sampling Date Range Sampling Mile Range Number of Captures
Colorado River Mar 31 - Nov 06 0 - 242.9 535
Gunnison River Apr 07 - Oct 20 0 - 57.1 90
Green River Mar 12 - Sep 25 120 - 381 2
Yampa River Mar 30 - Jun 30 0 - 194.1 1


Heatmap displaying the spatial distribution of bluegill captures within major rivers of the Upper Colorado River Basin


This chart has title 'Length Frequency for Bluegill by River'. The chart is comprised of 4 panels containing sub-charts, arranged horizontally. The panels represent different values of nm_rvr. Each sub-chart has x-axis 'Total Length' with labels 100, 200 and 300. Each sub-chart has y-axis 'Total Fish Encountered' with labels 0, 50 and 100. Panel 1 represents data for nm_rvr = Colorado River. Panel 1 is a bar chart with 13 vertical bars. It has colour set to black. Panel 2 represents data for nm_rvr = Green River. Panel 2 is a bar chart with 13 vertical bars. It has colour set to black. Panel 3 represents data for nm_rvr = Gunnison River. Panel 3 is a bar chart with 13 vertical bars. It has colour set to black. Panel 4 represents data for nm_rvr = Yampa River. Panel 4 is a bar chart with 13 vertical bars. It has colour set to black.



Green Sunfish


Hydrologic Area Sampling Date Range Sampling Mile Range Number of Captures
Colorado River Mar 31 - Nov 06 0 - 242.9 8151
Green River Mar 12 - Sep 25 120 - 381 519
Yampa River Mar 30 - Jun 30 0 - 194.1 307
Gunnison River Apr 07 - Oct 20 0 - 57.1 273
White River May 20 - Jun 19 29 - 104.3 185


Heatmap displaying the spatial distribution of green sunfish captures within major rivers of the Upper Colorado River Basin


This chart has title 'Length Frequency for Green Sunfish by River'. The chart is comprised of 5 panels containing sub-charts, arranged horizontally. The panels represent different values of nm_rvr. Each sub-chart has x-axis 'Total Length' with labels 0, 50, 100, 150 and 200. Each sub-chart has y-axis 'Total Fish Encountered' with labels 0, 200, 400 and 600. Panel 1 represents data for nm_rvr = Colorado River. Panel 1 is a bar chart with 12 vertical bars. It has colour set to black. Panel 2 represents data for nm_rvr = Green River. Panel 2 is a bar chart with 12 vertical bars. It has colour set to black. Panel 3 represents data for nm_rvr = Gunnison River. Panel 3 is a bar chart with 12 vertical bars. It has colour set to black. Panel 4 represents data for nm_rvr = White River. Panel 4 is a bar chart with 12 vertical bars. It has colour set to black. Panel 5 represents data for nm_rvr = Yampa River. Panel 5 is a bar chart with 12 vertical bars. It has colour set to black.



Grass Carp


Hydrologic Area Sampling Date Range Sampling Mile Range Number of Captures
Colorado River Mar 31 - Nov 06 0 - 242.9 10
Green River Mar 12 - Sep 25 120 - 381 5


Heatmap displaying the spatial distribution of grass carp captures within major rivers of the Upper Colorado River Basin


This chart has title 'Length Frequency for Grass Carp by River'. The chart is comprised of 2 panels containing sub-charts, arranged horizontally. The panels represent different values of nm_rvr. Each sub-chart has x-axis 'Total Length' with labels 750, 800, 850, 900 and 950. Each sub-chart has y-axis 'Total Fish Encountered' with labels 0, 1, 2, 3 and 4. Panel 1 represents data for nm_rvr = Colorado River. Panel 1 is a bar chart with 10 vertical bars. Bar 1 is centered horizontally at 760, and spans vertically from 0 to 0. Bar 2 is centered horizontally at 780, and spans vertically from 0 to 0. Bar 3 is centered horizontally at 800, and spans vertically from 0 to 4. Bar 4 is centered horizontally at 820, and spans vertically from 0 to 3. Bar 5 is centered horizontally at 840, and spans vertically from 0 to 0. Bar 6 is centered horizontally at 860, and spans vertically from 0 to 1. Bar 7 is centered horizontally at 880, and spans vertically from 0 to 0. Bar 8 is centered horizontally at 900, and spans vertically from 0 to 0. Bar 9 is centered horizontally at 920, and spans vertically from 0 to 0. Bar 10 is centered horizontally at 940, and spans vertically from 0 to 1. It has colour set to black. Panel 2 represents data for nm_rvr = Green River. Panel 2 is a bar chart with 10 vertical bars. Bar 1 is centered horizontally at 760, and spans vertically from 0 to 1. Bar 2 is centered horizontally at 780, and spans vertically from 0 to 0. Bar 3 is centered horizontally at 800, and spans vertically from 0 to 0. Bar 4 is centered horizontally at 820, and spans vertically from 0 to 3. Bar 5 is centered horizontally at 840, and spans vertically from 0 to 0. Bar 6 is centered horizontally at 860, and spans vertically from 0 to 1. Bar 7 is centered horizontally at 880, and spans vertically from 0 to 0. Bar 8 is centered horizontally at 900, and spans vertically from 0 to 0. Bar 9 is centered horizontally at 920, and spans vertically from 0 to 0. Bar 10 is centered horizontally at 940, and spans vertically from 0 to 0. It has colour set to black.



Brown Trout


Hydrologic Area Sampling Date Range Sampling Mile Range Number of Captures
Green River Mar 12 - Sep 25 120 - 381 1637
Gunnison River Apr 07 - Oct 20 0 - 57.1 113
Yampa River Mar 30 - Jun 30 0 - 194.1 72
Colorado River Mar 31 - Nov 06 0 - 242.9 31
White River May 20 - Jun 19 29 - 104.3 3
Vermillion Creek May 16 - May 16 0.1 - 0.1 1


Heatmap displaying the spatial distribution of brown trout captures within major rivers of the Upper Colorado River Basin


This chart has title 'Length Frequency for Brown Trout by River'. The chart is comprised of 6 panels containing sub-charts, arranged horizontally. The panels represent different values of nm_rvr. Each sub-chart has x-axis 'Total Length' with labels 200, 400 and 600. Each sub-chart has y-axis 'Total Fish Encountered' with labels 0, 50, 100, 150, 200 and 250. Panel 1 represents data for nm_rvr = Colorado River. Panel 1 is a bar chart with 27 vertical bars. It has colour set to black. Panel 2 represents data for nm_rvr = Green River. Panel 2 is a bar chart with 27 vertical bars. It has colour set to black. Panel 3 represents data for nm_rvr = Gunnison River. Panel 3 is a bar chart with 27 vertical bars. It has colour set to black. Panel 4 represents data for nm_rvr = Vermillion Creek. Panel 4 is a bar chart with 27 vertical bars. It has colour set to black. Panel 5 represents data for nm_rvr = White River. Panel 5 is a bar chart with 27 vertical bars. It has colour set to black. Panel 6 represents data for nm_rvr = Yampa River. Panel 6 is a bar chart with 27 vertical bars. It has colour set to black.



Rainbow Trout


Hydrologic Area Sampling Date Range Sampling Mile Range Number of Captures
Green River Mar 12 - Sep 25 120 - 381 51
Yampa River Mar 30 - Jun 30 0 - 194.1 22
Colorado River Mar 31 - Nov 06 0 - 242.9 18
White River May 20 - Jun 19 29 - 104.3 8
Gunnison River Apr 07 - Oct 20 0 - 57.1 3
Little Snake River May 28 - May 29 34.5 - 40 1


Heatmap displaying the spatial distribution of rainbow trout captures within major rivers of the Upper Colorado River Basin


This chart has title 'Length Frequency for Rainbow Trout by River'. The chart is comprised of 6 panels containing sub-charts, arranged horizontally. The panels represent different values of nm_rvr. Each sub-chart has x-axis 'Total Length' with labels 200, 400 and 600. Each sub-chart has y-axis 'Total Fish Encountered' with labels 0, 2, 4, 6 and 8. Panel 1 represents data for nm_rvr = Colorado River. Panel 1 is a bar chart with 27 vertical bars. It has colour set to black. Panel 2 represents data for nm_rvr = Green River. Panel 2 is a bar chart with 27 vertical bars. It has colour set to black. Panel 3 represents data for nm_rvr = Gunnison River. Panel 3 is a bar chart with 27 vertical bars. It has colour set to black. Panel 4 represents data for nm_rvr = Little Snake River. Panel 4 is a bar chart with 27 vertical bars. It has colour set to black. Panel 5 represents data for nm_rvr = White River. Panel 5 is a bar chart with 27 vertical bars. It has colour set to black. Panel 6 represents data for nm_rvr = Yampa River. Panel 6 is a bar chart with 27 vertical bars. It has colour set to black.



White Sucker


Hydrologic Area Sampling Date Range Sampling Mile Range Number of Captures
Yampa River Mar 30 - Jun 30 0 - 194.1 18367
White River May 20 - Jun 19 29 - 104.3 2952
Colorado River Mar 31 - Nov 06 0 - 242.9 2762
Green River Mar 12 - Sep 25 120 - 381 1901
Gunnison River Apr 07 - Oct 20 0 - 57.1 734
Vermillion Creek May 16 - May 16 0.1 - 0.1 61


Heatmap displaying the spatial distribution of white sucker captures within major rivers of the Upper Colorado River Basin


This chart has title 'Length Frequency for White Sucker by River'. The chart is comprised of 6 panels containing sub-charts, arranged horizontally. The panels represent different values of nm_rvr. Each sub-chart has x-axis 'Total Length' with labels 0, 200, 400, 600 and 800. Each sub-chart has y-axis 'Total Fish Encountered' with labels 0, 100, 200 and 300. Panel 1 represents data for nm_rvr = Colorado River. Panel 1 is a bar chart with 40 vertical bars. It has colour set to black. Panel 2 represents data for nm_rvr = Green River. Panel 2 is a bar chart with 40 vertical bars. It has colour set to black. Panel 3 represents data for nm_rvr = Gunnison River. Panel 3 is a bar chart with 40 vertical bars. It has colour set to black. Panel 4 represents data for nm_rvr = Vermillion Creek. Panel 4 is a bar chart with 40 vertical bars. It has colour set to black. Panel 5 represents data for nm_rvr = White River. Panel 5 is a bar chart with 40 vertical bars. It has colour set to black. Panel 6 represents data for nm_rvr = Yampa River. Panel 6 is a bar chart with 40 vertical bars. It has colour set to black.



Flannelmouth Sucker X White Sucker


Hydrologic Area Sampling Date Range Sampling Mile Range Number of Captures
Colorado River Mar 31 - Nov 06 0 - 242.9 501
Gunnison River Apr 07 - Oct 20 0 - 57.1 422
White River May 20 - Jun 19 29 - 104.3 168
Green River Mar 12 - Sep 25 120 - 381 142
Vermillion Creek May 16 - May 16 0.1 - 0.1 38
Yampa River Mar 30 - Jun 30 0 - 194.1 30


Heatmap displaying the spatial distribution of flannelmouth sucker x white sucker captures within major rivers of the Upper Colorado River Basin


This chart has title 'Length Frequency for Flannelmouth Sucker X White Sucker by River'. The chart is comprised of 6 panels containing sub-charts, arranged horizontally. The panels represent different values of nm_rvr. Each sub-chart has x-axis 'Total Length' with labels 200, 400 and 600. Each sub-chart has y-axis 'Total Fish Encountered' with labels 0, 20, 40 and 60. Panel 1 represents data for nm_rvr = Colorado River. Panel 1 is a bar chart with 27 vertical bars. It has colour set to black. Panel 2 represents data for nm_rvr = Green River. Panel 2 is a bar chart with 27 vertical bars. It has colour set to black. Panel 3 represents data for nm_rvr = Gunnison River. Panel 3 is a bar chart with 27 vertical bars. It has colour set to black. Panel 4 represents data for nm_rvr = Vermillion Creek. Panel 4 is a bar chart with 27 vertical bars. It has colour set to black. Panel 5 represents data for nm_rvr = White River. Panel 5 is a bar chart with 27 vertical bars. It has colour set to black. Panel 6 represents data for nm_rvr = Yampa River. Panel 6 is a bar chart with 27 vertical bars. It has colour set to black.



Bluehead Sucker X White Sucker


Hydrologic Area Sampling Date Range Sampling Mile Range Number of Captures
Colorado River Mar 31 - Nov 06 0 - 242.9 278
Gunnison River Apr 07 - Oct 20 0 - 57.1 256
White River May 20 - Jun 19 29 - 104.3 81
Green River Mar 12 - Sep 25 120 - 381 27
Yampa River Mar 30 - Jun 30 0 - 194.1 17
Vermillion Creek May 16 - May 16 0.1 - 0.1 2


Heatmap displaying the spatial distribution of bluehead sucker x white sucker captures within major rivers of the Upper Colorado River Basin


This chart has title 'Length Frequency for Bluehead Sucker X White Sucker by River'. The chart is comprised of 6 panels containing sub-charts, arranged horizontally. The panels represent different values of nm_rvr. Each sub-chart has x-axis 'Total Length' with labels 0, 100, 200, 300, 400 and 500. Each sub-chart has y-axis 'Total Fish Encountered' with labels 0, 10 and 20. Panel 1 represents data for nm_rvr = Colorado River. Panel 1 is a bar chart with 24 vertical bars. It has colour set to black. Panel 2 represents data for nm_rvr = Green River. Panel 2 is a bar chart with 24 vertical bars. It has colour set to black. Panel 3 represents data for nm_rvr = Gunnison River. Panel 3 is a bar chart with 24 vertical bars. It has colour set to black. Panel 4 represents data for nm_rvr = Vermillion Creek. Panel 4 is a bar chart with 24 vertical bars. It has colour set to black. Panel 5 represents data for nm_rvr = White River. Panel 5 is a bar chart with 24 vertical bars. It has colour set to black. Panel 6 represents data for nm_rvr = Yampa River. Panel 6 is a bar chart with 24 vertical bars. It has colour set to black.