Fly Fishing Advice at Orvis

The Rising Problem of Invasive Species

An Aquatic Nuisance Species, or ANS, is an invasive organism that can cause environmental harm or harm the health of humans or animals when it spreads to a location where it would not naturally occur. As the result of the emerging threat posed to our fisheries by various aquatic invasive species—for example, New Zealand mud snails, the whirling disease parasite Myxobolus cerebralis, and Didymo (filamentous algae)—many anglers, guides, outfitters, lodges, and fly shop owners have raised concerns regarding the proper care and cleaning of boats, trailers, and angling equipment to help prevent the spread of these nasty aquatic hitchhikers. 

Controlling ANS: How to Inspect, Clean, and Dry Boats and Fishing Equipment

Unfortunately, when it comes to stopping the spread of these vexing aquatic species, there is no safe and simple, universal, one-size-fits-all, silver bullet solution for neutralizing the various invasive aquatic flora and fauna. So, what can one do? To reduce the threat of aquatic hitchhikers, simply inspect, clean, and dry your fishing gear, boat, and trailer when moving between fishing locations, especially when moving from waters where Aquatic Nuisance Species are known to be present. While some ANS are visible, many are not, so due diligence is critical. 

ANS can hitch a ride in mud, debris, aquatic vegetation, and in water. In the case of boats, make sure all water is drained from the boat and live wells prior to leaving the waterbody. Inspect the boat and remove visible mud, plants, and debris before transportation, and rinse the boat and trailer at a car wash or with a garden hose as soon as possible. Rough patches on the boat may be zebra mussels or other invasive aquatic species that have attached and should be cleaned right away. If available, use a pressurized stream of water hotter than 140 degrees to clean your boat and trailer. 

For waders and angling gear, before you leave the river, rinse off the mud, debris, and vegetation. Inspect waders and boots to make sure nobody is hiding in the crevices and seams. A soft brush kept in the wader bag is useful when cleaning the boot seams. It is important to dry out your gear completely between trips. If sportsmen perform these relatively simple tasks, they’ll be doing their part to help prevent the spread of Aquatic Nuisance Species. 

What about Killing ANS with Chemical Treatments? 

While it is true that various chemical treatments have been identified that will kill some ANS—such as Formula 409 for mud snails and chlorine bleach or Sparquat for whirling disease spores—the chemical solutions that come the closest to preventing the spread are extremely harsh on equipment and are not safe for the environment. For example, while soaking wading gear in a solution of chlorine bleach and water will kill the whirling disease parasite, repeated use of this mixture will destroy the gear. And can you imagine what the fishing access site, nearby riparian zone, and river water might look (and smell) like if everyone who got out of the water doused their gear in bleach and Formula 409? 

If it is not feasible to completely dry your gear before you use it again, you may choose to use chemicals to disinfect prior to use elsewhere. Still,the best approach for the angling and sporting public to help prevent the spread of Aquatic Nuisance Species is to Inspect, Clean, and Dry—the simple guidelines of the Federation of Fly Fishers campaign, the Clean Angling Pledge. The Federation of Fly Fishers and Trout Unlimited have come together to request that every angler join in this effort by signing the Clean Angling Pledge

Eurasian Watermilfoil Didymo New Zealand Mudsnails
Eurasian Watermilfoil - Photo by Robert L. Johnson, Cornell University Didymo - Photo by Sarah Spaulding USGS/EPA Whirling Disease Infected Trout - Photo by Barry Nehring, Colorado Division of Wildlife New Zealand Mudsnails - Photo by D.L. Gustafon

For more information on Aquatic Nuisance Species visit

Dave Kumlien
Executive Director, Whirling Disease Foundation

Dave Kumlien is a former fly shop owner, current Montana fly fishing outfitter and was a charter member of Orvis’s Endorsed Lodge Outfitter and Guide program. He is currently the Executive Director of Trout Unlimited’s Bozeman, Montana based Whirling Disease Foundation.

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