News that didymo, the “rock snot” algae contaminating many prime trout streams, was not introduced via the damp felt of anglers’ wading boots, as previously thought, may be leading some anglers to become less careful about clean angling practices.
That could have serious impacts, because damp, dirty felt soles can and do transmit even more damaging invasive species like whirling disease spores and New Zealand mud snails, advocates say.
Felt-soled boots have provided traction on slippery underwater rocks for generations of anglers. But news that Didymosphenia geminata might be spread by damp felt inspired many anglers to switch to modern, “sticky rubber” soles to prevent contaminating more streams.
Some state governments have banned felt soles, and many more have launched educational campaigns urging anglers to “Check, Clean and Dry” their gear after fishing one lake or stream and before moving to another.
The fly-fishing tackle industry now sells a wide range of wading shoes with soles made of “sticky” materials like Vibram. Still, some anglers don’t trust the rubber soles to be as safe as grippy felt. Some resented the need to buy new equipment. And some are skeptical of the notion of transporting aquatic nuisance species altogether.
So when scientists announced new research showing that didymo hadn’t been transported but was in fact already present and had begun blooming because of environmental factors, clean angling advocates saw a disturbing trend of anglers going back to the old ways.
“One of the things I am encountering as fallout (from the new research) is that the ‘naysayers’ in the angling community are taking the position that the whole clean angling, eliminate the use of felt soles effort is bogus, and that we don’t have to worry about our boots or waders any longer,” said David Kumlein, director of Trout Unlimited’s Aquatic Invasive Species Program. Kumlien ran a fly shop in Bozeman, Mont. for 20 years and has been executive director of the Whirling Disease Foundation.
While “it’s good news to know that the cause of some of the Didymo problems aren’t the result of anglers’ boots and waders, there’s still the potential to move Didymo to a place where it wasn’t native, and the bigger threat is that there are other AIS (aquatic invasive species) that we know do move on boots, i.e. New Zealand mud snails,” Kumlein said.
By one estimate, anglers moved more than 6,300 pounds of sediment in felt soles among fishing access points in southwestern Montana in 2005, and out-of-state anglers carried 1,600 pounds of sediment into the state. The potential for that sediment to contain spores of whirling disease, mud snails and other AIS is what troubles advocates like Kumlein.
Canadian scientist Max Bothwell, who first proposed the theory that a new, fast-blooming variant of didymo was being spread by felt sole wading boots, has revised his opinion based on new research. Didymo had been known to be native to North America, and further investigation has shown it has begun blooming in recent years because of dropping levels of phosphorous in streams.
However, Bothwell said didymo can be tracked into places where it’s not native, which is probably what happened in New Zealand, where rock snot has damaged a number of high-quality trout rivers.
So switching from felt soles – and checking, cleaning and drying equipment including shoes, no matter what kind of sole – is still essential, Kumlein said.
At a didymo conference in 2013, he recalled, “following my comments regarding ‘staying the course’ on clean angling, Max Bothwell gave an impassioned plea to the conference audience to not use his new research as a reason to abandon the clean angling effort.”