Fly-Fishing: Rock snot theory changes

When the “rock snot” didymo algae started blooming in beloved trout streams across the region and ar

When the “rock snot” didymo algae started blooming in beloved trout streams across the region and around the country in the mid-2000s, most of us believed the theory that the nuisance was being carried from river to river in the damp felt soles of anglers’ shoes.

It seemed perfectly plausible, since didymo spores had been shown to live a long time in damp felt, and many of us have been known to fish a stream while our felts were still wet from the last one.

An article in “Fisheries” mag­azine in 2009, titled “On the Boots of Fishermen: The History of Didymo Blooms on Vancouver Island, British Columbia,” seemed to cement the idea in the trout fishing establishment. The next thing you knew, states were banning felt soles, advoc­acy groups were begging anglers not to use them and tackle companies all but stopped selling them.

Wading shoes with so-called sticky rubber soles became the norm.

Now, the author of “On the Boots of Fishermen” has changed his mind.

Further research has led Max Bothwell of Environment Canada to a new conclusion: Didymo is native to all of North America and already present in many streams. What’s new are the blooms, and Bothwell and colleagues have discovered the blooms are caused by a change in the environment — low levels of phosphorous in the water, which causes didymo to grow the long stalks that become streambed-smothering mats in the worst cases.

“I no longer believe the problem with didymo in North Amer­ican streams is the result of it being moved around” by fishermen, Bothwell told me for an article in the July/August issue of “American Angler” magazine.

In fact, Bothwell and other scientists added phosphorous to a badly affected stretch of stream in North Dakota, and the didymo bloom there shrank.

Bothwell said he does not regret his influential “On the Boots of Fishermen” theory. In fact, he said, anglers should still avoid felt, since it has been shown to carry all kinds of invasives, including whirling disease (which, by the way, thrives in streams with didymo blooms.)

Not all anglers were willing to take the blame for the didymo blooms in the Battenkill River, the branches of the Delaware and Kayaderosseras, Esopus and Schoharie creeks. Many pointed out that wildlife and non-angling humans could also spread spores from stream to stream.

They were also annoyed at the idea of being forced to buy a new piece of gear, and one they didn’t trust, at that. After all, previous attempts at non-felt soles were a bust. They just didn’t grip underwater rocks as well as felt.

One of them was Ed Ostapczuk of Shokan in Ulster County. Ostapczuk is no skeptic of environmental science in general; on the contrary, he played an important role in the passage of a state law in 1976 that required releases from New York City reservoirs that would protect the trout fisheries downstream, and helped kill a disastrous idea for a pumped water storage power plant in the Catskills.

I wasn’t surprised that Ostapczuk found the new thinking about didymo fascinating. But in view of his reluctance to abandon felt for safety reasons, I was surprised to hear his view on modern rubber soles.

“I am a CONVERT,” Ostapczuk said in an email. “I love the Simms Vibram sole wading shoes with studs. I personally believe that these grip the stream bottom better than felts.

“So who knows what the true cause [of didymo blooms] is? I don’t … but I’ve shifted from felt wading shoes to Vibram soles cause I think they are better for fishing/wading.”

I do too. I’ve been wearing Vibram-soled shoes for several seasons. They grip well enough in the water, and they’re much nicer for walking to the water.

And while I may not, in fact, have helped halt the “spread” of didymo, it’s nice to know I may have helped keep other nasty invasives out of our trout streams.

The next step is to figure out why rivers across North America and elsewhere are suddenly starved of phosphorous. And correcting that problem is likely to be much more complicated than getting anglers to wear different shoes.

Categories: Sports

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