For the past few years, we fly-fishers have heard a lot of advice about how to prevent spores of didymo, the “rock snot” algae fouling some of our favorite streams, from being spread from place to place on our wading shoes.
The advice ranges from 30-minute boot baths in scalding water to a delousing with Formula 409. But researchers at Bard College have done some tests in the lab, and concluded that the most effective didymo cleaner is ordinary dish soap. It did a better job than bleach solution, Virkon (a commercially available disinfectant) or salt solution.
The finding was published in the October issue of Fisheries, the journal of the American Fisheries Society.
What to do about didymo has become a real issue in the trout fishing world. Since 2006, it has been found in some of New York’s best-loved trout streams, including the Battenkill River, Esopus Creek, Schoharie Creek, the branches of the Delaware River and even Kayaderosseras Creek.
At its worst, didymo becomes a thick mat of stringy algae that smothers the streambed. In other areas, notably New Zealand, it has ruined trout streams.
So far in the northeastern United States, didymo has been an intermittent nuisance, blooming and dying back. While it does not seem to have harmed trout or aquatic insects, it gunks up subsurface flies, makes for slippery wading and generally diminishes the fishing experience.
The Bard College researchers didn’t just examine didymo in the lab. They also looked at the various efforts to inform anglers about how to avoid spreading it — and found confusing and conflicting advice.
“Recommendations from state agencies in the northeastern United States varied widely,” the researchers found. “Some state agencies only suggested one decontamination method, whereas others offered as many as six different techniques. In New York State, identifying a proper decontamination method can be especially confusing because the signs posted at fishing access sites offer decontamination instructions that differ from the state’s Department of Environmental Conservation website.”
There’s plenty of signage along streams where didymo already exists, but almost none at other popular waters (the West Branch of the Ausable in the Adirondacks being a notable exception). Seven out of 10 anglers surveyed for the study said no information about didymo was posted where they fish.
The study recommends more consistent messaging along the country’s trout streams, including accurate photos (some of the most-viewed images show New Zealand didymo, which doesn’t look like the American kind).
Also suggested were cleaning stations at popular access points. (At “high priority” sites in New Zealand, the report says, you can’t even get a license to fish unless the licensing agent actually watches you disinfect your shoes first.)
The study suggests changing the phrase “Check, Clean and Dry” to “Check, Clean and Treat,” because felt waders take a long time to dry — and didymo can live in damp felt for more than a month.
Finally, “we strongly recommend banning felt-soled waders,” the study’s authors said.
Felt soles already are banned in Alaska, Maryland, Missouri, Rhode Island and Vermont — despite objections from some anglers who consider felt soles important safety equipment for wading streams.
Many anglers object to being forced to buy waders with “sticky” rubber soles, and they note that waders, flies, canoes, inner tubes, animals and birds could all spread the diatom, too.
This is a legitimate concern. Still, felt soles seem to be going the way of neoprene waders — still available, but not used very much anymore. While it’s true that flies, canoes, inner tubes, animals and birds can also spread didymo, most experts agree that felt soles practically seem designed for the purpose.
I’ve used Simms wading shoes with Vibram “sticky rubber” soles, augmented with a few sheet metal screws, for several seasons now, and don’t feel my safety is compromised. In some situations, like hiking on leaves or snow, I like them better. And the soles won’t peel off after a few seasons like felts do.
Our trout streams face enough challenges. Here’s hoping we keep didymo from infesting any more.
Morgan Lyle’s commentary appears regularly in The Daily Gazette. Reach him at firstname.lastname@example.org.