YELLOWSTONE NATIONAL PARK — On a crisp, overcast August morning, a group of four fly fishermen waded patiently in Soda Butte Creek, trying to attract the trout.

Over a four-hour span Friday, the men caught only three smallish cutthroat trout, which they immediately released back into the chilly water.

But it was a successful morning, according to Bill Voigt, co-coordinator for Yellowstone National Park's Volunteer Fly Fishing Program.

The group wasn't fishing purely for fun, Voigt said.

The anglers had a task: Keep an eye out for brook trout, or "brookies," a non-native species introduced Yellowstone's ecosystem decades ago by park managers who wanted to keep the lakes and rivers stocked with an ample supply of trout for sport fishermen.

The brookies you could — and were required — to keep.

If one of the men landed a brookie, an olive-green to dark brown fish with silvery sides and spots, they were instructed to place it in a yellow bucket to be measured and weighed later.

There were no brookies caught Friday morning, which was a good sign, Voigt said.

Park scientists have been working for years to combat the threat that non-native fish, including brook trout, pose to the park's native fish population, namely the Yellowstone and westslope cutthroat trout and the Arctic grayling.

The foreign fish compete with the native species for food and space, and interbreeding between rainbow and cutthroat trout has resulted in hybridized, or "genetically impure" cutthroat in the Bechler, Falls, Gallatin, Gardner and Lamar rivers, and the Yellowstone River below the Upper Falls.

But other aquatic issues in the thousands of miles of streams and lakes in the 2.2 million-acre park, issues such as whirling disease and lake trout removal, have proved increasingly time-consuming for the fisheries staff.

That's where the volunteers come in, Voigt said. Since 2002, the National Park Service staff has enlisted the help of recreational anglers to gather biological information on fish populations in Yellowstone.

Volunteers travel from across the country to participate in the program, which runs from June to September, Voigt said. He usually leads groups of about four anglers on eight to 12-hour catch-and-release fishing excursions aimed at collecting research for projects outlined by park biologists at the beginning of the summer.

Under Voigt and co-coordinator Tim Bywater's tutelage, the anglers track fish population numbers, distribution and movement patterns. Weight, length, species, distinguishing features and data such as stream water levels and temperatures, are meticulously logged by Voigt and turned over to researches at the end of the summer.

It's what Voigt, a former civil engineer, calls "citizen science."

Funded primarily by the Yellowstone Park Foundation, the program provides free lodging on Yellowstone Lake for volunteers. They're responsible for their gear and a daily sack lunch.

Volunteers are crucial to the park's efforts to protect and restore native fish, said Al Nash, park spokesman.

"A lot of people want to give back to the park, and volunteering is a way to do so," Nash said. "We have a small fisheries staff, and they cannot be out everywhere all the time. (The fishermen) are an educated set of eyes and ears, and they're able to get out there and gather information that we just couldn't get otherwise."

Weigh, measure, photograph

Volunteer Brent McKell, one of the four anglers on Soda Butte Creek Friday, has been involved with the program since its inception eight years ago, when he heard about it through his fishing club in Salt Lake City.

He said that although the days are long, it affords him the opportunity to visit out-of-the-way fishing spots he would never find otherwise.

"It's a lot of fun, and it's a lot of work," he said. "We cover a ton of area in all kinds of weather. (But) when you can pair fly fishing and Yellowstone, it's a good combination."

By tapping the willingness and expertise of such civilian enthusiasts, scientists can expand the park's network of researchers and gather more information, Voigt said.

"We're able to go out and fish these streams and collect the data the biologists either don't have the time or the manpower for," he said.

He said scientists are able to use their data from particular sections of streams to extrapolate conditions for a complete watershed.

"Over the years, our data has proved out what they're finding, too," he said.

For instance, if the volunteers come across a concentration of brook or brown trout, Voigt can mark the spot using GPS technology, which park biologists can then use to find the population and remove it.

Last year, Voigt, his wife Joann and a group of volunteers hiked into Heart High Lake to check on a westslope cutthroat trout population they had been actively tracking for five years. Earlier studies had indicated that all of the westslopes were hybrids, so scientists started a hatchery there to try to restore the native population. The aim was to determine whether there were any pure westslopes in the lake.

The Voigts and the volunteers spent two solid days weighing, measuring and photographing every one of the 65 fish they caught. They also noted the presence or absence of an intact adipose fin, located on the back behind the dorsal fin, on each fish. The hybrids had their adipose fins clipped; pure westslopes would be intact.

What they found was exciting: The hatchery had been successful, and there was a population of pure westslope cutthroat living among the hybrids.

"They're really positive about the data we collected last year," Voigt said. "In a couple years, there's going to be a pretty good fishery up there."

"It was kind of neat to be involved from the very beginning up until last year and to see the results," Joann Voigt said.

Fish & volunteer at same time

On Friday, the Bill Voigt supervised on Soda Butte Creek included two men from New York and two from Salt Lake City. All were experienced anglers, so Voigt let them work, occasionally asking questions about the conditions from the stream bank.

Mike Kelly, a retired stockbroker from New York, said he found out about the program in a magazine article. He had been to Yellowstone twice before and thought this sounded like the perfect excuse to return.

"I saw the photos in the article and thought, ‘Wow, that is heaven sent,'" Kelly said. "Where else do you get to fish and volunteer at the same time?"

Voigt, who is retired, said most of the people he takes out are also retirees, but there are young couples and families who volunteer too. Anyone is welcome, regardless of fishing experience.

"We don't turn people away," he said. "We don't care if you're a beginner or advanced. All you have to be able to do is enjoy fly fishing."

Voight said coordinating the program has given him an opportunity to see the park in a different way, too.

"Every day's a new experience here," Voigt said. "Even though it's the same scenery, the light's different. Sometimes you see a bear. Sometimes you see a wolf. Where else can you have so much fun in such a beautiful place"

Lauren Russell can be reached at lrussell@dailychronicle.com or 582-2635.

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