‘Rock snot’ showing up early in the year near Ruedi dam

Fryingpan didymo study earns financial support from Pitkin County commissioners

An ongoing effort to study the increasing amounts of didymo in the Fryingpan River has received funding from Eagle and Pitkin counties, and will assess any potential effects the algae is having on the fishery.

Didymo, which is also known by the less tantalizing name of “rock snot,” is a native, nuisance species of algae that thrives in low-nutrient, cold-water streams.

But it is being seen in prodigious amounts on the Fryingpan near the Ruedi dam, leading some to hypothesize that it’s being spread there by the large number of fishermen who wade through the shallow waters.

Heather Lewin, watershed action director for the Roaring Fork Conservancy, made a presentation before the Pitkin County commissioners on Tuesday, explaining the supplemental study’s goals, and outlining information already gleaned from work in the river.

She explained that the study, which is being conducted by the Roaring Fork Conservancy and Colorado Mountain College-Leadville’s natural resource management program, aims to measure the health of the Fryingpan River and fishery.

Lewin explained that didymo (Didymosphenia geminata) attaches to rocks in rivers and streams, takes up a lot of habitat for macroinvertebrates, and is spreading at a high rate.

“There are a lot of unknowns around didymo,” she said. “It lives in areas where you don’t generally find algae. … There’s concern as didymo populations increase, that you see a decrease in macroinvertebrate populations, which in turn is detrimental to fish populations.”

Lewin added that didymo is present in around 20 percent of Colorado’s streams and rivers.

The study has also led some to hypothesize that higher release flows from Ruedi Reservoir have a “scouring effect” on the algae, cleaning the rocks and flushing the didymo downstream, where it stops growing once it meets still water.

“If you get the water moving fast enough, either it can pull the didymo itself, or roll the rocks and clean the [algae] off,” Lewin explained. “We did see a significant decrease after [high flows].”

She said that other studies in the state show that didymo thrives below dams, and local testing shows it is present in the Upper Fryingpan, but only at microscopic levels.

Fishermen spreading ‘rock snot?’

Another theory being studied this year is whether fisherman carry the algae from one river access point to another on their boots and waders.

“The other piece is working with anglers and other river users to make sure we’re cleaning waders and boots as people come in and out of the river,” Lewin said. “Not only as they transfer rivers but as they transfer to different parts of the river. … It doesn’t take much to spread didymo.”

A cleaning station for fishing gear was set up on the Fryingpan by the Roaring Fork Valley Fly Fishing Club last summer, and is expected to be back this year.

The study also will look into the seasonality of the algae blooms, and study spreading patterns to help draft management practices.

Lewin noted that the conservancy hasn’t done studies on didymo in the Roaring Fork River, but the algae hasn’t been reported in as large amounts there as in the Fryingpan.

A supplemental budget request from Pitkin County’s Healthy Rivers and Streams Fund was approved in the amount of $10,000 for the study to continue. The granted amount mirrored the offering from Eagle County, which is also supporting the effort.

“It sounds like the Fryingpan River could potentially be in jeopardy of being a Gold Medal fishery because of this,” said Commissioner Steve Child. “So we’re inclined to learn a little more about this, and keeping the river healthy would be [the goal].”

 

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