The Joplin Globe, Joplin, MO

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August 24, 2013

Anglers, conservationists working to prevent algae dubbed 'rock snot' from spreading in Missouri

CASSVILLE, Mo. —  Longtime fly fisherman Paul Niegsch peppers riverbank conversations with the occasional odd phrase, such as “wooly bugger,” “crackleback” and “Copper John.”

In March 2012, he added a new term to that vocabulary: “didymo.”

“I hadn’t ever heard of it until I saw the signs,” said Niegsch, a Kansas resident who frequents Missouri’s many trout streams.

Since then, didymo has become all too familiar to anglers.

It also has become a topic of conversation among those responsible for the health of Missouri’s streams and rivers. Hatchery managers and conservationists have, essentially, garrisoned the borders of the state in hopes they can keep it out.

A single-celled algae, didymo — the scientific name is Didymosphenia geminata — blooms in freshwater rivers and streams with consistently cold water temperatures and just the right pH level.

It forms large mats that blanket river and stream beds, critically altering habitats and cutting off food sources for fish. It could wreak havoc at trout fisheries such as Roaring River State Park or in other cold-water streams in the state.

The ill will that anglers and conservationists have toward didymo is reflected in the nickname they have given it: rock snot.

“It can also make fishing impossible — or nearly impossible,” said Paul Spurgeon, who manages the Missouri Department of Conservation trout hatchery at Roaring River State Park, south of Cassville.

Didymo, a non-native, invasive species, has expanded in recent years to 18 states, including to a 13-mile stretch of the White River in neighboring Arkansas, where it was found in 2005.

“That’s very, very close, and a lot of anglers who fish there (White River) also come to Missouri rivers and streams to fish,” Spurgeon said.

Beaver Lake in Arkansas and Table Rock and Taneycomo lakes in Missouri are part of the White River basin, all upstream from where it was found just south of the Missouri-Arkansas line; Roaring River also empties into Table Rock Lake near Eagle Rock.

Missouri Department of Conservation experts say the state’s spring-fed trout streams, with a water temperature of around 57 degrees, provide ideal conditions for didymo to flourish.

“It’s microscopic,” Spurgeon said of the algae. “One drop is all it would take.”

Mats of didymo can easily detach from the stream bed and float downstream on their own, expanding its range naturally. But it also can be transferred between bodies of water on an angler’s porous, felt-soled waders or fishing gear, prompting a ban of felt-soled waders in Missouri in 2012.

Felt-soled waders had been a popular choice for anglers because they provide better traction on slippery river surfaces than some other traditional options, such as rubber.

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