Eurasian Watermilfoil, Robyn Draheim, CC NC

Aquatic Nuisance Species - Eurasian Watermilfoil

Invasive Wildlife

Aquatic Nuisance Species

Aquatic nuisance species (ANS) are invasive plants and animals that harm lakes, reservoirs, rivers and streams; invasive species can also include non-native viruses and parasites that cause disease in fish. ANS do damage to not just Colorado’s native species, but its economy, public health, property values and parks. 

Threats to Colorado

Quagga Mussel, NPS

Zebra and Quagga Mussels

Zebra, quagga and golden mussels are considered the most serious threat to Colorado’s waters. They attach themselves in large, densely packed groups to water storage, treatment and distribution systems, causing clogs and other disruptions. This causes devastating problems for municipal, agricultural and industrial infrastructure.

new zealand mudsnail

​​​​​​​​​​​​​​​New Zealand Mudsnails

New Zealand mudsnails are an invasive freshwater snail. Being voracious eaters that reproduce rapidly, they deplete aquatic habitats of food for native species, damaging ecosystems in the process. Aquatic insect larvae, native snails and fish are all affected. These mudsnails are also able to pass through a fish's digestive system unharmed, leaving the fish malnourished — and the mud snail free to eat, reproduce and do more damage to the surrounding habitat.

Rusty Crayfish

Rusty Crayfish

​Rusty crayfish are native to the Ohio River Basin, and may have been introduced to Colorado by anglers using them as bait. Being larger and more aggressive, they outcompete native crayfish for food and habitat. These crayfish will eat aquatic insects, small fish and fish eggs. They also eat aquatic vegetation, which native fish rely on for spawning, cover and food.

Eurasian Watermilfoil

Eurasian Watermilfoil

Eurasian watermilfoil (EWM) is an aquatic noxious weed that forms dense mats on the water’s surface, which restrict swimming, fishing and boating. The mats shade and choke out native aquatic plants that aquatic fish and animals rely on for shelter, habitat and food. The decaying plants foul beaches and decrease oxygen levels in the water, destroying habitat and food for fish and birds. The mats slow the flow of water in ditches, rivers and streams, creating ideal mosquito habitat. EWM clogs water intakes and alters water chemistry, changing the taste and smell of drinking water. EWM reproduces by seeds, fragmentation and winter buds. Any plant fragment can start a new infestation.

Infected Waters in Colorado

    ​South Platte River (just below Eleven Mile dam in Park County)

    ​South Platte River (just below Eleven Mile dam in Park County)

    Positive since 2004

    ​Boulder Creek

    ​Boulder Creek

    Positive since 2004

    ​Green River within Dinosaur National Monument

    ​Green River within Dinosaur National Monument

    Positive since 2005

    Dry Creek, City of Boulder

    Dry Creek, City of Boulder

    ​South Delaney Buttes State Wildlife Area

    ​South Delaney Buttes State Wildlife Area

    Positive since 2010

    East Delaney Buttes State Wildlife Area

    East Delaney Buttes State Wildlife Area

    Positive since 2010

    ​Eleven Mile Reservoir State Park

    ​Eleven Mile Reservoir State Park

    Positive since 2011

    Charlie Meyer State Wildlife Area

    Charlie Meyer State Wildlife Area

    Positive since 2011

    College Lake, Colorado State University

    College Lake, Colorado State University

    Positive since 2011

    Spinney Mountain State Park

    Spinney Mountain State Park

    Positive since 2011

    ​Fountain Creek

    ​Fountain Creek

    Positive since 2012

    Chatfield Reservoir

    Chatfield Reservoir

    Positive since 2013

    Gunnison River (West of Delta)

    Gunnison River (West of Delta)

    Positive since 2015

    Fourmile Canyon Creek (Boulder County)

    Fourmile Canyon Creek (Boulder County)

    Positive since 2016

    Monument Lake

    Monument Lake

    Positive since 2017

    South Platte River (Near Deckers)

    South Platte River (Near Deckers)

    Positive since 2017

    ​Uncompahgre River (Town of Montrose)

    ​Uncompahgre River (Town of Montrose)

    Positive since 2017

    ​Jimmy Camp Creek

    ​Jimmy Camp Creek

    Positive since 2017

    Monument Reservoir

    Monument Reservoir

    Positive since 2018

    ​Trinidad Lake

    ​Trinidad Lake

    Positive since 2018

    Lake Capote

    Lake Capote

    Positive since 2018

    Chatfield Pond #1

    Chatfield Pond #1

    Positive since 2019

    ​Elmer’s 2 Mile Park (Boulder County)

    ​Elmer’s 2 Mile Park (Boulder County)

    Positive since 2019

    South Platte River (City of Denver)

    South Platte River (City of Denver)

    Positive since 2019

    Trout Creek

    Trout Creek

    Positive since 2020

    South Boulder Creek

    South Boulder Creek

    Positive since 2020

    Antero Reservoir

    Antero Reservoir

    Positive Since 2024

    ​South Platte River (just below Eleven Mile dam in Park County)

    ​South Platte River (just below Eleven Mile dam in Park County)

    Positive since 2004

    ​Boulder Creek

    ​Boulder Creek

    Positive since 2004

    ​Green River within Dinosaur National Monument

    ​Green River within Dinosaur National Monument

    Positive since 2005

    Dry Creek, City of Boulder

    Dry Creek, City of Boulder

    ​South Delaney Buttes State Wildlife Area

    ​South Delaney Buttes State Wildlife Area

    Positive since 2010

    East Delaney Buttes State Wildlife Area

    East Delaney Buttes State Wildlife Area

    Positive since 2010

    ​Eleven Mile Reservoir State Park

    ​Eleven Mile Reservoir State Park

    Positive since 2011

    Charlie Meyer State Wildlife Area

    Charlie Meyer State Wildlife Area

    Positive since 2011

    College Lake, Colorado State University

    College Lake, Colorado State University

    Positive since 2011

    Spinney Mountain State Park

    Spinney Mountain State Park

    Positive since 2011

    ​Fountain Creek

    ​Fountain Creek

    Positive since 2012

    Chatfield Reservoir

    Chatfield Reservoir

    Positive since 2013

    Gunnison River (West of Delta)

    Gunnison River (West of Delta)

    Positive since 2015

    Fourmile Canyon Creek (Boulder County)

    Fourmile Canyon Creek (Boulder County)

    Positive since 2016

    Monument Lake

    Monument Lake

    Positive since 2017

    South Platte River (Near Deckers)

    South Platte River (Near Deckers)

    Positive since 2017

    ​Uncompahgre River (Town of Montrose)

    ​Uncompahgre River (Town of Montrose)

    Positive since 2017

    ​Jimmy Camp Creek

    ​Jimmy Camp Creek

    Positive since 2017

    Monument Reservoir

    Monument Reservoir

    Positive since 2018

    ​Trinidad Lake

    ​Trinidad Lake

    Positive since 2018

    Lake Capote

    Lake Capote

    Positive since 2018

    Chatfield Pond #1

    Chatfield Pond #1

    Positive since 2019

    ​Elmer’s 2 Mile Park (Boulder County)

    ​Elmer’s 2 Mile Park (Boulder County)

    Positive since 2019

    South Platte River (City of Denver)

    South Platte River (City of Denver)

    Positive since 2019

    Trout Creek

    Trout Creek

    Positive since 2020

    South Boulder Creek

    South Boulder Creek

    Positive since 2020

    Antero Reservoir

    Antero Reservoir

    Positive Since 2024

    Yampa River

    Yampa River

    Positive since 2009

    Catamount Reservoir

    Catamount Reservoir

    Positive since 2009

    Sanchez State Wildlife Area

    Sanchez State Wildlife Area

    Positive since 2010

    Stagecoach Reservoir State Park

    Stagecoach Reservoir State Park

    Positive since 2011

    Granby

    Granby

    Yampa River

    Yampa River

    Positive since 2009

    Catamount Reservoir

    Catamount Reservoir

    Positive since 2009

    Sanchez State Wildlife Area

    Sanchez State Wildlife Area

    Positive since 2010

    Stagecoach Reservoir State Park

    Stagecoach Reservoir State Park

    Positive since 2011

    Granby

    Granby

    Adobe Creek SWA

    Adobe Creek SWA

    Arkansas River

    Arkansas River

    Arvada Reservoir

    Arvada Reservoir

    Aurora Reservoir

    Aurora Reservoir

    Bear Canyon Creek

    Bear Canyon Creek

    Bessemer Ditch

    Bessemer Ditch

    Big Dry Creek

    Big Dry Creek

    Blue Heron Ponds

    Blue Heron Ponds

    Boulder Creek

    Boulder Creek

    Boulder Reservoir

    Boulder Reservoir

    Bow Mar Lake

    Bow Mar Lake

    Bowles Reservoir

    Bowles Reservoir

    Brush Hollow Reservoir

    Brush Hollow Reservoir

    Charlie Meyer SWA

    Charlie Meyer SWA

    Chatfield Reservoir

    Chatfield Reservoir

    Cherry Creek Reservoir

    Cherry Creek Reservoir

    CU Ponds in Boulder

    CU Ponds in Boulder

    Douglas Reservoir

    Douglas Reservoir

    Eleven Mile State Park

    Eleven Mile State Park

    Fountain Lake

    Fountain Lake

    Gateway Reservoir (Private)

    Gateway Reservoir (Private)

    Horseshoe and Martin Reservoirs in Lathrop SP

    Horseshoe and Martin Reservoirs in Lathrop SP

    Lon Hagler Reservoir

    Lon Hagler Reservoir

    Lowell Ponds

    Lowell Ponds

    Marston Reservoir

    Marston Reservoir

    Lake Minnequa

    Lake Minnequa

    Minnequa Canal (Fremont Canal)

    Minnequa Canal (Fremont Canal)

    Monument Lake

    Monument Lake

    Navajo Reservoir (NM Side)

    Navajo Reservoir (NM Side)

    North Poudre Reservoir #4

    North Poudre Reservoir #4

    Palmer Lake

    Palmer Lake

    Panama Reservoir #1

    Panama Reservoir #1

    Pathfinder Park Pond

    Pathfinder Park Pond

    Pavlakis Open Space

    Pavlakis Open Space

    Pella Crossing Ponds

    Pella Crossing Ponds

    Prospect Lake

    Prospect Lake

    Lake Pueblo

    Lake Pueblo

    Pueblo Steel Mill

    Pueblo Steel Mill

    Rio Grande River

    Rio Grande River

    Saint Charles Reservoir #2, #3

    Saint Charles Reservoir #2, #3

    Saint Vrain Creek

    Saint Vrain Creek

    Saint Vrain State Ponds

    Saint Vrain State Ponds

    Sawhill Ponds

    Sawhill Ponds

    San Isabel Lake

    San Isabel Lake

    Sheets Lake

    Sheets Lake

    Skaguay Reservoir

    Skaguay Reservoir

    South Platte River

    South Platte River

    Standley Lake (Westminster)

    Standley Lake (Westminster)

    Swift Ponds

    Swift Ponds

    Tucker Lake

    Tucker Lake

    Tule Lakes

    Tule Lakes

    Walden Pond

    Walden Pond

    Ward Road Ponds

    Ward Road Ponds

    Wellington Reservoir #4

    Wellington Reservoir #4

    West Lake

    West Lake

    West Prospect Park Lake

    West Prospect Park Lake

    Adobe Creek SWA

    Adobe Creek SWA

    Arkansas River

    Arkansas River

    Arvada Reservoir

    Arvada Reservoir

    Aurora Reservoir

    Aurora Reservoir

    Bear Canyon Creek

    Bear Canyon Creek

    Bessemer Ditch

    Bessemer Ditch

    Big Dry Creek

    Big Dry Creek

    Blue Heron Ponds

    Blue Heron Ponds

    Boulder Creek

    Boulder Creek

    Boulder Reservoir

    Boulder Reservoir

    Bow Mar Lake

    Bow Mar Lake

    Bowles Reservoir

    Bowles Reservoir

    Brush Hollow Reservoir

    Brush Hollow Reservoir

    Charlie Meyer SWA

    Charlie Meyer SWA

    Chatfield Reservoir

    Chatfield Reservoir

    Cherry Creek Reservoir

    Cherry Creek Reservoir

    CU Ponds in Boulder

    CU Ponds in Boulder

    Douglas Reservoir

    Douglas Reservoir

    Eleven Mile State Park

    Eleven Mile State Park

    Fountain Lake

    Fountain Lake

    Gateway Reservoir (Private)

    Gateway Reservoir (Private)

    Horseshoe and Martin Reservoirs in Lathrop SP

    Horseshoe and Martin Reservoirs in Lathrop SP

    Lon Hagler Reservoir

    Lon Hagler Reservoir

    Lowell Ponds

    Lowell Ponds

    Marston Reservoir

    Marston Reservoir

    Lake Minnequa

    Lake Minnequa

    Minnequa Canal (Fremont Canal)

    Minnequa Canal (Fremont Canal)

    Monument Lake

    Monument Lake

    Navajo Reservoir (NM Side)

    Navajo Reservoir (NM Side)

    North Poudre Reservoir #4

    North Poudre Reservoir #4

    Palmer Lake

    Palmer Lake

    Panama Reservoir #1

    Panama Reservoir #1

    Pathfinder Park Pond

    Pathfinder Park Pond

    Pavlakis Open Space

    Pavlakis Open Space

    Pella Crossing Ponds

    Pella Crossing Ponds

    Prospect Lake

    Prospect Lake

    Lake Pueblo

    Lake Pueblo

    Pueblo Steel Mill

    Pueblo Steel Mill

    Rio Grande River

    Rio Grande River

    Saint Charles Reservoir #2, #3

    Saint Charles Reservoir #2, #3

    Saint Vrain Creek

    Saint Vrain Creek

    Saint Vrain State Ponds

    Saint Vrain State Ponds

    Sawhill Ponds

    Sawhill Ponds

    San Isabel Lake

    San Isabel Lake

    Sheets Lake

    Sheets Lake

    Skaguay Reservoir

    Skaguay Reservoir

    South Platte River

    South Platte River

    Standley Lake (Westminster)

    Standley Lake (Westminster)

    Swift Ponds

    Swift Ponds

    Tucker Lake

    Tucker Lake

    Tule Lakes

    Tule Lakes

    Walden Pond

    Walden Pond

    Ward Road Ponds

    Ward Road Ponds

    Wellington Reservoir #4

    Wellington Reservoir #4

    West Lake

    West Lake

    West Prospect Park Lake

    West Prospect Park Lake

     

    Highline Lake and the Colorado River (in Grand Junction) have tested positive for zebra mussels. 

    Out of State
    Colorado is experiencing a significant increase in the amount of mussel infested boats being intercepted at lakes and reservoirs across the state. While these boats are coming in from all directions, the majority are originating from Lake Powell (72%).

    Invasion of mussels from out-of-state waters continues to be a threat, and will likely increase. Almost all states to the east of Colorado have a zebra or quagga mussel infestation. The closest is Cedar Bluff Reservoir which is only 150 miles from our border in Kansas. The southwest US has many widespread infestations including Lake Powell, Lake Mead, Lake Mohave, and Lake Havasu, which are all frequented by Colorado boaters.

    Protect Colorado's Waters

    Invasive species of plants and wildlife harm Colorado's land and water, negatively impacting the state’s economy, recreation, property values and public health. Invasive wildlife spread by hitchhiking on watercraft, trailers, vehicles, tires, boots, waders, equipment, gear, firewood and even dogs! Cleaning gear before and after use can help prevent the spread of aquatic nuisance species.