Anglers who have had the misfortune of stumbling across didymosphenia geminata, or didymo, usually don't forget the experience. The invasive yellow-brown algae species goes by a more colorful—and, sadly, physically accurate—name: rock snot. To the naked eye, it looks like giant chocolate-flavored gummy worms coating the riverbed, or the aftermath of some enormous Yeti's sneeze.
"It's nasty stuff," says David Kumlien, director of Trout Unlimited's Aquatic Invasive Species Program. "It looks like wet, wadded-up toilet paper at the bottom of the river. It's easy to see how it ruins things."
Persistent rock snot can choke out a stretch of river, killing aquatic life. Even mild outbreaks—like those found in Montana's Kootenai and Bitterroot rivers—can destroy a pristine trout stream by sticking to anglers' lines, lures and wet flies.
- New Zealand Fish and Game
Rock snot first hit headlines in the early 1990s, when the formerly benign alga began acting like an invasive species and took over streams in British Columbia, Canada. To date it has spread across North America and into parts of Europe, Asia, South America, and New Zealand.
Recreationists can spread the single-celled organism by carrying it on their boats, kayaks, lifejackets, waders and, in particular, felt-soled boots. The footwear has become an especially hot-button issue within the last year.
Trout Unlimited called for manufacturers to phase out felt-soled fishing boots by 2011; if not properly cleaned, the boots can transport rock snot, whirling disease and other watershed threats. Vermont and Maryland enacted legislation banning felt boots in April, and Alaska will enact a similar law next year. Other states continue to consider legislation; a proposed felt ban during Montana's last legislative session failed to make it out of committee.
While felt remains a problem, experts believe the recent fixation actually distracts from a larger issue. Broader education and outreach—like Montana's "Inspect. Clean. Dry" campaign—are crucial to combating all invasive aquatic organisms.
"There are a lot of different ways to approach it, but by keeping the message simple like [Montana's], states have a much higher likelihood of success and compliance," says Kumlien. "If you make it too complicated, like a chart with chemical treatments for your gear for all of these aquatic invasive species, then you'll lose people."
Case in point: Kumlien is charged with updating Trout Unlimited's national educational materials about invasive organisms, including rock snot. He plans to follow Montana's blueprint.
In the meantime, the rock snot problem isn't going away. Montana Sen. Tom Facey, who sponsored the failed felt-ban bill, says he still believes it's a vital issue. The proposed legislation fell victim to politics—"We found key players this session had limited resources and bigger fish to fry, pun intended," he says—but that shouldn't deter Montana from continuing the fight against invasive aquatic species.
"This is important," Facey says. "We can only hope the industry continues to step up and take care of it themselves."