Oregon has always been about its waters, rivers in particular.

Oregon has always been about its waters, rivers in particular.

Now some of the folks who love them most face a grim dilemma: Are fly fishers and others who would wear felt-soled waders posing an invasive species threat to the waterways?

Felt has long been the way to go. It grips slippery rocks like nothing else, offering sure footing in surging streams.

But felt is a porous mat and holds water like a sponge. If not cleaned properly, the soggy sole from last week's fishing venture in British Columbia may well store microorganisms that could live long enough to be transported to a favored fishing spot in the Umpqua, Willamette or Deschutes basins.

Once delivered, if the microorganism's name is didymo, large tissuelike mats on the river bottom could start to choke out native plants and invertebrates and limit the food chain.

That's what happened in New Zealand, which banned felt-soled waders, and more recently in Alaska and Vermont, whose legislatures passed felt-sole bans waiting to take effect in 2012 and 2011 respectively.

But Oregon has not yet seen the diatom didymo, whose blooms are more commonly known as rock snot. Didymo is so feared, however, that in 2006 it made it onto the Oregon Invasive Species Council's "hit list" of worst critters to be kept out of Oregon waters.

Trout Unlimited and the Native Fish Society have lobbied Salem legislators to enact, in the 2011 session, a ban on felt-soled wading boots. Fine. But the problem goes beyond felt soles to other parts of the boot that also offer unseen creatures a free ride to the next waterway: laces, tongues, uppers.

That makes improperly cleaned and dried gear the real culprit, though few disagree that felt is a prime offender.

Oregon already faces complication in the New Zealand mud snail, an invasive that has taken hold in waterways up and down the coast and in the Deschutes basin. The size of a grain of sand, the mud snail is suspected of arriving here via several sources, one of them the felt-soled waders of fishers.

Few people know didymo's threat, however, better than Bob Wiltshire of the Center for Aquatic Nuisance Species in Montana. Though he reviewed and verified the science indicting felt-soled waders as delivery vehicles for didymo, Wiltshire says the critter will stay on the move until fishing gear goes retro: to a one-piece rubber boot and wader combination that is easily cleaned and dried.

Such gear now is aimed at the lower end of the market, and its upgrade would require new rubber compounds and more fitting options. But to do so would also require a sensibility shift among Oregon fishers, not to mention an overhaul of a boot market tooled for comfort, custom fit and sure-footed security.

Nobody wants to slip on the rocks, we get that. But didymo could seriously affect our rivers. Measures to prevent its arrival, including a possible felt ban, should be seriously examined.

Boot makers are successfully trying out new sticky rubber treads as well as swappable soles, yet getting away from felt won't be the only challenge. Proper cleaning and storage of all submerged gear worn in the river — and the education needed to make that happen — are every bit as important.