Guest Blogger: Anchor Fly

Many fly anglers became aware of the threat of aquatic invasive species about a decade ago, when felt soled wading boots were implicated in the spread of Didymo and whirling disease, leading to felt bans in several states, and the discontinuation (at least briefly) of felt-soled wading boots by Simms. Since then, the threats in the U.S. have continued to multiply, affecting fisheries and aquatic ecosystems throughout the country.

invasive species feature

Overview Of Spread | Visible Examples

Those of us who live or fish in the West have also seen a proliferation in the state-mandated watercraft inspection and decontamination stations along main roadways since invasive mussels were found in Lake Mead in 2007[i]. In the Midwest, new reports chronicle the efforts of fish and game agencies to control invasive carp[ii]. First introduced in the Mississippi River drainage to control weeds in canal systems, carp have escaped into the rivers, in some cases entirely eliminating native fish species in local streams. In the southern US, invasive lionfish threaten both commercial and recreational fisheries, and the very existence of the remaining coral reef ecosystems in the western North Atlantic[iii].


In Alaska, fisheries managers are struggling to eliminate the aquatic weed Elodea spp. This is a fast-growing aquarium species that probably got into the rivers when people dumped the contents of their fish tanks, thinking nothing could survive in Alaska’s cold waters.

Unfortunately, Elodea thrives in slow-moving cold water, impervious to both freezing and drying, growing so rapidly it blocks light and outcompetes all other plant life. As it increases in density, it slows flows, and traps sediments and fine particles that then settle out into spawning gravels, effectively smothering them. Eventually, its own growth causes it to crash, but in death and decomposition, it uses up so much of the available oxygen in the water that other species struggle to survive.[iv]

These high-visibility examples of aquatic invasive species are only a few of the threats we face.

Aquatic Invasive Species (AIS) | Definition

Generally speaking, the term aquatic invasive species (AIS) include all animals, plants and pathogens that have spread outside their native range, and that have a competitive edge over native species, either infecting them with disease, preying on them directly, altering their habitat, or consuming the native species’ food resources.

Deformed Brook Trout
Whirling Disease in Brook Trout

Intentionally Introduced

Sometimes, invasive species have been intentionally introduced by anglers, as in the case of Northern Pike in California[v], or walleye in Idaho’s Lake Pend Oreille, where they preyed on and outcompeted native trout and salmon.[vi] In some cases, no one has identified the origin of an invasion. In Yellowstone National Park, for example, lake trout “appeared” in Lake Yellowstone in 1994. By 2005, the population was close to a million fish, with catastrophic impacts to the park ecosystem.

Spawning cutthroat numbers fell from 50,000 in the 1980s to less than 500, and soon, the eagles, osprey and bears that depended on spring spawners for food began spreading out in search of other nutrient sources, like swans and baby mammals. While park biologists have recently started to gain the upper hand in controlling lake trout, the effort is costing the park over $2 million each year.[vii]

Invasive Plant Species

Invasive plant species can also impact trout populations. In lake and pond ecosystems, introduced plants like flowering rush, non-native common reed, giant salvinia and water hyacinth quickly colonize open water. While this can be beneficial to the young of some fish species, it reduces spawning opportunities for others, and provides cover for lie-in-wait predators, gradually altering fish population composition. And in some cases, water hyacinth and giant salvinia can create such dense mats that oxygen exchange is limited, affecting fish growth and even survival.[viii]

eichhornia crassipes
Water Hyacinth
Salvinia Molesta

How Much Are Anglers Implicated In The Spread Of Invasives?

So how much are anglers implicated in the spread of invasives? Clearly, the “bucket biologists” who intentionally introduce non-native fish species into lakes and rivers are among the worst offenders, as are those bait fishers who know better, but who dump their remaining live bait into waterways at the end of the day.[ix] Any boater who plots their route to or from a favorite spot to avoid watercraft inspection has a serious case of indifference to the problem. But those of us who simply switched from felt to rubber soles and called it good are also part of the problem. Who among us hasn’t put on damp waders in the morning, or visited a couple of different streams in a single day, or travelled between watersheds on a weekend angling trip? And how many of us pay attention to the less-obvious ways we can introduce invasives, like carrying seeds or other plant materials on the Velcro closures on sandals or vest patches?

What Can Anglers Do To Help Stop The Spread?

If we are genuinely concerned about the health of aquatic ecosystems and fisheries, there are a number of actions we can all take

1. Know The Enemy.

First, know the enemy. If you don’t know what Didymo looks like, get online and find out. Know which streams and rivers in your home watershed have reported whirling disease, and make sure to do your homework before you venture out (and return from) a new place.

Find out what the threats are in your home state, and the states that border you.

The United States Geological Survey maintains an excellent website for Nonindigenous Aquatic Species at, where you can search for invasive species information by state, drainage, or species, and view both presence and threat maps. I just touched on invasive invertebrates in this article; the USGS site has listings for 70 invasive clam and mussel species.

2. Take Time To Take Care

Second, take time to take care. Regardless of what kind of soles you use, regard your wading footgear as potential sources of contamination. Cleaning your boots, waders, sandals, net, and other gear is a pain, especially in the middle of the day when you’ve decided to head for your next favorite stream. But do it anyway. I often carry two sets of wading gear when I think I might switch streams mid-day: boots and chest waders for the cool morning, hip waders or nylon pants with sandals for the afternoon if temperatures permit. If that is out of reach for you, invest in a stiff brush, a heavy plastic container, a plastic tub and a gallon of disinfectant so you can move from one stream to another without risking the spread of invasives. While chlorine bleach solutions will work against many aquatic invasive species, bleach is also hard on your gear. Instead, both for work and recreation, I follow the recommendations of multiple state and federal agencies and use a quaternary ammonia compound.[x] I mix Super HDQ neutral (available from Amazon), at a ratio of 6 oz to a gallon of water, and keep it in a dedicated 7 gallon water jug (labelled TOXIC with a sharpie). After thoroughly brushing my boots and wader seams, I stick them in the plastic tub, pour the disinfectant solution over them, and sort my flies for ten minutes. A good brushing that removes mud and debris will also keep the solution clean enough to pour back into the container and use again. If you don’t travel between streams on the same day, you can disinfect at home. Or, if you are looking for a less labor-intense solution, try freezing. While there are some reports that mussels can withstand freezing, brushing your waders and boots and tossing them into a chest freezer overnight should kill most organisms. Hot water is another option: after brushing, soak waders and boots in water hotter than 115 F for 15 minutes. [xi] The hottest tap water in most homes and motels will exceed that temperature. Although I don’t know of any studies to support it, there is anecdotal support for the idea that running your boots through a clothes dryer on hot for long enough to completely dry them will also kill invaders.


3. Watercraft

Third, when you use a watercraft –whether it’s a boat, a paddleboard, a kayak or a float tube- follow the Inspect, Drain, Clean and Dry protocol. Pick all visible debris off and leave out to dessicate. If you have a hard sided watercraft, run your hand across the hull; if it feels like sandpaper, you may have picked up mussels.

Didymo Sign

 Drain any chamber or well that may contain water (including the bow and stern of your sit-in kayak). Clean the watercraft with hot water (140 degrees F), pressure wash it, or, if you live in a state with disinfecting stations, run it through their wash. Leave everything to dry thoroughly before reusing.

4. Get Involved

Fourth, get involved. The University of Georgia has created its WildSpotter App for smartphones so that you can report the invasives you encounter. Depending on your state, there may be similar, state-specific apps you can use. Check with your local watershed group or Trout Unlimited to find invasive species removal events. Many of these events have been on hold during the pandemic, leaving aquatic invasive plants plenty of opportunity to expand; as the country reopens, expect more volunteer cleanup events to expand as well.

5. Be Bold

Finally, be bold. Challenge your bait-fishing friends and family to find out exactly what species they’re buying when they pick up live bait. Pay attention to your kids’ school science projects: are they raising guppies in bowls filled with Elodea? Look for water garden displays at your local garden center and find out exactly what they’re selling; you’ll be surprised how heavily “fast growing water hyacinth” is promoted. Make a stink about it. Question what you bring into your own garden, and find out what might happen if it escapes to nearby riparian areas. And talk to the anglers you meet. The pandemic has dramatically increased the number of new fly anglers; according to a Redington marketing manager I spoke with, the fly fishing industry hasn’t seen a run on gear this large since A River Runs Through It was released, and, he said, this new wave of interest far surpasses even that one. This means that we have more people with less knowledge of invasive species moving around in our favorite streams. Instead of just grumbling about how they’re taking over, spend time talking to them to make sure overcrowding isn’t the only negative impact they bring.

See Our Anchor Fly’s Acquatic Invasive Species Infographic HERE


  1. Interesting topic, and it’s always on the minds of us all, but…”just grumbling”??? This isn’t that crowd. Regarding “who among us” never does the things you mentioned, well, me for one. Never…and it’s not by accident either. Yourself? And I’d put good money on a bet that nobody in this intelligent, disciplined, purist fly-tying readership has ever stocked fish from one water to the next.

    It’s my personal belief that authorities have historically been the ones most guilty of a lack of humility regarding watershed species. Lake Tahoe has Kokanee and Coho salmon in it, not naturally and not because of purist anglers either. Rivers are flooded with “tiger trout” to control other smaller species, with authorities claiming the stocked predators are pre-sterilized…but their ability to compete against the local fish populations is still there, and regarding reproduction and proliferation, I hate to call the scientists careless, but, well, life does find a way. We hear stories of rabbit introduction in Australia but we still haven’t learned the lesson. And then there are what can only be considered misguided attempts to restore this or that stream to “original” by poisoning and starting anew, assuming an “original” can even be identified across the eons (which is impossible given the spectrum Nature relentlessly paints), and tempting a world of repercussions stemming from differences in come-back speed of every fish, every crustacean, every insect.

    Monkeying with things invites — assures — the unexpected.

    I know that snakeheads are encroaching at rapid rates across America, but it’s not fly tiers doing that. I know alligators migrate overland and take fish species with them; ditto for birds of prey and bobcats. I know the pesky crustaceans of recent note are in fact thought to be a risk only to man-introduced and man-managed drainage pipes, not to fish populations, and I know that those who can’t afford to pay a ten-spot every time to get their plastic kayak inspected — the kayak they haven’t had out for half a year but that got rained on the week before in the back yard…or that maybe was used a week earlier but in the same lake — are not the problem either.

    This is indeed a serious topic, but in my humble opinion it’s not a solution to pin blame on private fishermen, no matter how popular an approach that is to authorities. We are more than willing to bail authorities out on this, to be the solution to what they’ve done in the past, and to help our fisheries in the process, but we want to see some humility. Nature is itself the best one at fixing things long-term, and we need to know that in our souls. In my opinion ways need to be adopted that drop the accusatory fingers and dispense with the punishment of individuals, and instead offer respect, and carrots, to get behind a good plan, a plan that’s ultimately based on a core concept of letting Nature fix things softly and surely.

    If our authorities dispense with the arrogant bio-warfare of introducing species to waters, claiming they’ll be that water’s saviors, it would be a big step in the right direction. Humility and respect is the key; man’s misguided schemes only complicate and make matters worse.

    Bad attitude? One could try to say that. I think it’s on the right track nonetheless.

    Again this is an interesting and important topic. I believe strongly in the people on this forum.

    – Mike

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