Aquatic Nuisance Species (ANS)

What are Aquatic Nuisance Species?

Aquatic Nuisance Species (ANS) are aquatic plants and animals that invade lakes, reservoirs, rivers and streams. Examples of ANS include:

  • Zebra mussel
  • Quagga mussel
  • New Zealand mudsnail
  • Asian carp
  • Rusty crayfish
  • Eurasian watermilfoil. 

ANS can also include fish pathogens and diseases, such as viral hemorrhagic septicemia (VHS) or whirling disease.  

What are Invasive Species?

Invasive species are plants, animals, insects or diseases that are not native to Colorado and have harmful negative effects on the economy and environment. They are introduced accidentally or intentionally outside of their native range. Because they are not native to Colorado habitats, they have no natural competitors or predators. Without these checks and balances, the invaders are able to reproduce rapidly and out-compete native species. Invasive species have harmful effects on natural resources and disrupt our use of land and water.

Why Do They Matter?

Invasive species...

  • Damage Colorado’s lands and waters
  • Hurt the economy
  • Ruin recreation opportunities
  • Threaten public health
  • Damage or impair infrastructure

Many invasive species consume enormous amounts of water and reduce the water supply for livestock, wildlife, native vegetation, and humans. These species can change the physical characteristics of land and water and alter food chains. As habitat is destroyed by invasive species, the wildlife that depends on it disappears as well. About 42% of the species on the Federal Threatened or Endangered Species lists are at risk primarily because of invasive species. In the United States, ecological damage and control of invasive species cost $200 billion per year and these costs are increasing. Colorado’s environment draws tourists, brings business, and supports agriculture. To protect it, we must manage invasive species quickly.

Click here to learn more about ANS

ANS Stamp Requirement for 2023

Motorboats and sailboats must have an ANS Stamp prior to launching in Colorado. 

Colorado residents can purchase an ANS stamp while registering the motorized (gas or electric) watercraft. For already registered motorboats and sailboats, ANS Stamps can be purchased online at or at any CPW office or sales location. 

Exempt watercraft are not required to purchase an ANS Stamp, they include:

  • Kayak
  • Paddleboard
  • Canoe
  • Raft
  • Belly Boat
  • Windsurfer Board
  • Inner Tubes

ANS Stamp FAQ's

Colorado is a Mandatory Boat Inspection State 

All trailered and/or motorized (gas or electric) watercraft are required to be professionally inspected for ANS by state-certified personnel: 

  • prior to launching in any water of the state after boating in a different state, 
  • upon exiting any water in the state which is positive for an invasive species, and 
  • any time an inspection is requested prior to entering or exiting a water body in Colorado.

Boat inspection and decontamination stations in Grand County are below:

  • Three Lakes (Grand Lake, Shadow Mountain Reservoir, and Lake Granby)
  • Williams Fork Reservoir
  • Wolford Mountain Reservoir

Every boater is required in regulation to Clean, Drain, and Dry your boat, trailer and equipment every time you enter or exit any waters.

Boater's Guide to ANS Inspections