Game and Fish concerned about larval form of invasive mussels found in the Snake River in Idaho


9/21/2023 10:49:51 PM

Cheyenne - The threat of invasive mussels to Wyoming’s waters continues to escalate with now five of the six bordering states containing populations of zebra or quagga mussels. Earlier this week the Idaho State Department of Agriculture (ISDA) confirmed the presence of quagga mussels veligers (larvae) in the Centennial Waterfront Park area of the Snake River. Currently, the positive area does not include the Snake River above Shoshone Falls. 

The detection of the veligers is significant as Wyoming remains one of the few states yet to have the destructive species. The Wyoming Game and Fish Department is concerned about the potential impacts this detection could have on Wyoming, especially the inadvertent movement of invasive mussels into the state through watercraft movement. Outside of the recent Snake River findings, ISDA has not found live quagga mussel larvae in any other Idaho waterbody and this is the first detection within the uninfested Columbia River Basin. 

“We are confident in Idaho’s robust AIS program and the actions they are taking to initiate containment, but are still confronting this aggressively,” Josh Leonard, Game and Fish AIS coordinator said. “Game and Fish is increasing our diligence to inspect and decontaminate watercraft coming from the area.” 

This is the second time in less than one year that quagga and zebra mussels have been found in a body of water close to the Wyoming border. The discovery is concerning as many boaters frequent waters on both sides of the state line. 

Mussels can spread easily, even in their microscopic state, from just a little water left standing on a boat.  If AIS — or the possibility —  is found on watercraft, Game and Fish will decontaminate the boat and educate boaters on how to reduce transmission of these threats themselves to make the next inspection quicker. 

It’s state law that all boaters must stop when coming upon an AIS inspection station — even if they stopped at one prior. Any watercraft transported into Wyoming from March 1-Nov. 30 must undergo a mandatory inspection by an authorized inspector prior to launching on any Wyoming waterway. A list of inspection locations is available online.

If boaters entering Wyoming do not encounter an open AIS check station on their route of travel, it is the boater’s responsibility to seek out an inspection. Further, if the watercraft was used on a water suspect or positive for invasive mussels in the last 30 days, it must be inspected prior to launching year-round and may require decontamination. Full rules are available online. 

Game and Fish is committed to working with ISDA and closely monitoring the situation on the Snake River in Idaho. Game and Fish will make adjustments to inspection protocols and boater requirements if needed to protect our waters. 

What are quagga mussels? Quagga mussels have emerged alongside zebra mussels as one of the most aggressive invasive species infesting the United States. These mussels spread easily to new areas due to the movement of watercraft.  A veliger is the free-swimming larval stage of a quagga mussel. Veligers are microscopic and cannot be seen with the naked eye. Veligers grow quickly and develop hair-like filaments and shells within a few weeks. Once the veligers find a suitable surface to attach to, they stick themselves to the surface using the hair-like protrusions and develop into adults. 

The adult mussels are highly competitive and persistent. Zebra and quagga mussels have the potential to cause fishery collapses, damage to boats and motors, hazards to swimmers and waders, poor water quality, and significant damage to water treatment facilities, hydroelectric power generators and irrigation systems. Since Wyoming is a headwater state, these impacts would cascade down the Columbia, Colorado and Missouri river drainages if they become established here.

(Breanna Ball, Public Information Officer - (

- WGFD -

  • fishing
  • regulations
  • information

Checking your CWD test results is easy

Hunters who had tissue samples from their deer, elk or moose collected for chronic wasting disease testing can check the results on the Game and Fish website

Continue reading...

Wyoming teen recognized as one of the state’s youngest Ultimate Anglers

Lander angler is the third 15-year old to accomplish this feat

Continue reading...

Keep your mule deer wild

Wildlife managers remind residents to resist the urge to feed backyard deer this winter

Continue reading...

2024 Wyoming Wildlife calendar now available

Marvel at the charismatic animals of Wyoming with the magazine's annual calendar issue calendar

Continue reading...

Waterfowl hunters be aware of license and stamp requirements

Be sure to have all your licenses and stamps before heading afield 

Continue reading...

Hunters reminded to submit harvest surveys

Elk, deer and antelope respondents can win great prizes

Continue reading...

Email Newsletter

Email Newsletter Sign Up

Stay up to date on all Wyoming Game and Fish news either by email or text message. Click the link below to get started.

Sign Up Today


Conserving Wildlife - Serving People