dont give nasty invaders a helping foot

Felt-soled wading boots are meant to keep anglers from slipping on wet rocks. Ironically, the felt sole, designed for greater purchase and "a nice solid point of contact on the river bottom," may ultimately cause more slippage.

By Erling Friis-Baastad

Felt-soled wading boots are meant to keep anglers from slipping on wet rocks. Ironically, the felt sole, designed for greater purchase and “a nice solid point of contact on the river bottom,” may ultimately cause more slippage, says Yukon Environment’s Senior Fisheries biologist Nathan Millar. The porous material may help introduce slimy algae into streams, he says. That’s one of the reasons why jurisdictions around North America are banning, or considering bans, on felt-soled waders in their waters.

Yukon anglers will encounter such a ban in Alaska next year.

“Humans are the main vectors for moving invasive species around,” says Millar. And two species of special concern these days are an algae, Didymosphenia geminata, or the unsightly, downright disgusting, “rock snot,” and a microparasite, Myxobolus cerebralis, that attacks the nervous system of fish and causes fatal “whirling disease.”

“The felt, in particular, is troublesome because of the nature of the material,” says Millar. “There’s a lot of space in felt and it remains wet for a long time. This keeps small organisms alive for a long time.” The waders could hang in a garage or a cupboard long after the a fishing trip has ended, and the organisms picked up during that trip will remain moist and alive, so that during the next fishing trip, to another body of water, those organisms can be transplanted, “without your knowledge or consent,” says Millar.

Multicellular didymo, which forms thick mats, is present in the Yukon, says Millar. But we don’t know how long it has been here. “It may in fact be native to the Yukon.” For now, it is not present in all of our waters and anglers are being encouraged to keep it that way for as long as possible. “It’s known to affect a number of things in the aquatic food chain. Because it grows in big mats it would change the composition of aquatic insects and benthic organisms … this has consequences as you move on through the food chain. It’s a whole ecosystem thing.”

Near the bottom of the food chain fish feed on creatures like caddis flies, dragonflies, and mayflies. All these insects have aquatic larvae so they need a home in the rocks in streams. “The algae is going to come in and disrupt the habitat, so they are not going to do very well.”

Didymo is especially ugly, as its nick-name would suggest, and, surprisingly, is not confined to slow or stagnant water. In fact, says Millar, it seems to thrive in nutrient-poor faster waters. Didymo can also be confused with other algae species. “To confirm its identity you need to look at it under a microscope.” Didymo contains little “Coke-bottle-shaped” silica structures.

“What we’re doing is starting to identify locations in the Yukon where didymo exists,” says Millar. But it’s a time for prevention not panic, he adds.

“You don’t want to go out and scare people. We want to give people good information so they can make commonsense behavioural choices that will help prevent the spread of many species, and are generally good practices – cleaning gear, removing any weeds….

“A lot of it is preventative. The evidence from every other jurisdiction around the world is that invasive species are inevitable in some form or other … What we can do is minimize their numbers and the speed at which they arrive.”

As for whirling disease, which attacks fish nervous systems, causing them to swim in circles before they die: “We don’t know if we have it here yet,” says Millar. “Or even if it would survive. It requires an intermediate host.” Of course, warming associated with climate change could improve the chances for the parasite’s survival. We could lose our cold-water advantage.

Meanwhile, what if some Yukon angler were to use felt-soled boots in waters of far different ecosystems, say in the lower Mississippi drainage? Would that bring other foreign organisms into the territory? We don’t have examples of that here yet, says Millar, but the potential is certainly real. In today’s world of high-speed transportation, organisms that might once have been stranded in one particular region can now travel about handily.

Not long ago, he received a report about a boat from eastern Canada that was trailered to Alaska. It was turned back into the Yukon at the Alaska border because it carried zebra mussels, which along with creatures like Asian carp and lampreys, are causing havoc in eastern freshwater fisheries.

Millar stresses that when it comes to invasive species, an ounce of prevention is worth a pound of cure. It’s far less expensive to prevent an invasion than to respond to one once it’s underway, he says. Inspect and clean boat hulls. Clean gear. Put boots in a freezer for four hours to kill off hitchhikers. Meanwhile, manufacturers are developing new, slip-resistant but less-porous soles for fishing boots. They’ve already caught on in New Zealand and would appear to be the wave of our future.

For more information on how to help prevent the spread of invasive species into your favourite fishing hole check out this year’s territorial fishing regulations at

For more on invasive species in general go to

This column is co-ordinated by the Northern Research Institute at Yukon College with major financial support from Environment Yukon and Yukon College/ The articles are archived at