MOUNTAIN LAKE MYSTERY

Planted trout disappearing from popular Beartooth Mountain lakes

2012-11-25T00:00:00Z 2012-11-26T07:56:05Z Planted trout disappearing from popular Beartooth Mountain lakesBRETT FRENCH french@billingsgazette.com The Billings Gazette

Trout planted at three Beartooth Mountain lakes — Beartooth, Long and Island lakes — are rapidly disappearing from the waters, and fish biologist Jason Burckhardt is trying to figure out why.

“The fish we were stocking were all but disappearing the following year,” said the Wyoming Game & Fish Department biologist.

A common factor among all three high mountain lakes is that they lie along Highway 212, the Beartooth Scenic Highway, which funnels hundreds of Montana, Wyoming and nonresident anglers past the waters every summer. The other Wyoming lakes in the Beartooths are farther off the pavement, so they receive less fishing pressure.

Solving the problem could be simple.

“If we’re finding there’s quite a bit of harvest, we could stock more catchable-sized fish,” Burckhardt said. “Or if we have other limiting factors, we could try other options.”

Stocked up

At Beartooth Lake alone, Wyoming last year and again this year stocked about 2,750 rainbow and Yellowstone cutthroat trout — 5,500 total. The stocked fish are 4 to 5 inches long. In addition, the lake contains naturally reproducing brook trout and a small population of lake trout, used to thin the stunted brook trout and to provide anglers with a larger fish to catch.

When Burckhardt’s crew set four nets on the lake overnight in late summer to gauge how the planted fish population was doing, they found few of the stocked fish present. The goal was to capture one fish per net hour, instead they only caught .75 on average.

“Seventeen percent of the population was stocked trout based on what our nets were seeing,” Burckhardt said.

The fish they were catching in their nets seemed to be healthy, though.

“If we are stocking fish that are too small, they may not have enough energy reserves to get through the winter,” Burckhardt said.

Asking anglers

To figure out what’s going on, Wyoming placed angler survey boxes at the three lakes to collect information. They also dispatched employees to interview anglers about what types of fish they were catching, how long it takes them to catch fish and what fish and how many were they keeping. The survey should give Wyoming Game and Fish an idea of how big a contribution stocked fish are making to anglers’ creels. The survey data still need to be compiled to provide any clues, Burckhardt said. More fish sampling and angler surveys are scheduled for this coming summer.

“We probably didn’t gather enough information this summer to make any recommendations on management,” he added.

Fishing regulations for the lakes are fairly liberal. Anglers are allowed to keep six trout and 16 brook trout daily or as a total possession limit. The limit can also include six lake trout, no more than one of which can exceed 24 inches.

Stocking change

The more remote lakes in Wyoming’s portion of the Beartooth Mountains are being stocked every other year, usually by helicopter. Through 2010, Wyoming Game and Fish was stocking the more accessible lakes in the same manner, but last year the agency decided to cut the number of stocked fish in half at Beartooth, Long and Island lakes but to stock them every year.

The department’s prescription for its mountain lakes is to stock 100 fish per surface acre of the lake. The growth rates for fish in the cold waters is traditionally about 2 to 3 inches a year, Burckhardt said.

He noted that although brook trout can be predacious, there’s little evidence those fish are gobbling down the planted trout. The brook trout are only averaging about 8 inches, a little too small to be dining on fish half their size. Lake trout are also predacious, but Burckhardt isn’t seeing enough of them to indicate that they are having a big impact on the number of stocked fish.

“It’s not a huge effort up there,” Burckhardt said. “We probably had about 40 to 50 interviews, not an overwhelming number. But we’ll be intensifying our efforts to see if we can get a better handle on how the stocked fish are contributing to the overall fish population.”

Crandall Creek

As Wyoming Game and Fish tries to figure out what’s happening on the Beartooth Plateau, down below on Crandall Creek, a tributary to the Clarks Fork of the Yellowstone River, there’s no doubt what occurred.

Once a stronghold for Yellowstone cutthroat trout, Crandall Creek has been overrun by rainbow trout that swam upstream. The rainbow trout interbred with the cutthroats, diluting their genetics.

None of the waters in the Wyoming section of the Beartooth Mountains initially contained fish. That’s because there are a series of high waterfalls on the Clarks Fork as it negotiates the steep-sided Box Canyon just south of the Montana-Wyoming border. So although the Clarks Fork is formed in the Beartooths, there were originally no fish on the upper Clarks Fork or its tributaries.

Wyoming’s fish stocking records go back to the 1920s. But Burckhardt said there is no notation on how the Yellowstone cutthroat trout arrived in Crandall Creek. The popular theory, which has never been tested, is that the fish came from the Yellowstone National Park hatchery. So the fish originally planted in Crandall Creek would have been the genetic offspring of a Yellowstone Lake cutthroat population that has now crashed to historic lows due to disease, drought and predation by introduced lake trout.

In 2011, the agency sampled Crandall Creek’s fish with the hope that the cutthroat population could be protected. In that scenario, rainbow trout would have been removed from sections of the stream and a barrier installed to keep them out. Instead, the agency found that the stream was already thick with rainbows and the mixed offspring of rainbow-cutthroat interbreeding.

“It’s an extensive drainage with lots of tributaries, there were about 60 miles of stream that the Yellowstone cutthroat trout occupied,” Burckhardt said. “Now it’s one of those places that’s been lost.”

This year, the agency also found that another drainage that once contained cutthroat had been invaded — Grinnell Creek, a tributary to the North Fork of the Shoshone River.

“The rainbow trout had invaded to the point that we are no longer able to consider that a conservation population,” Burckhardt said.

That’s a loss of about 10 to 15 miles of connected cutthroat habitat.

Burckhardt called the loss of the prime cutthroat fisheries “disheartening,” but said it makes the state’s efforts to secure other waters, such as in the Bighorn Mountains, all the more important. The Yellowstone cutthroat is now found in only about half of the miles of stream that the fish originally called home in Wyoming.

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