"Yellowstone Lake is home to the largest population of Yellowstone cutthroat trout in existence"..........."This population plays a critical role in the ecosystem, transporting nutrients from lake waters to tributary streams during spawning and to the terrestrial (land) system when the fish are eaten by birds and mammals".............."Also, cutthroat trout have a predominant influence on the structure of the lake community, including zooplankton and phytoplankton"............."They have provided a world-renown angling opportunity for more than a century, drawing fly fishermen from around the globe and contributing $36 million annually to local economies".........."Lake trout, however, are voracious, efficient predators that frequently live 20-25 years and are able to reach large sizes—50 lbs".............."Their large size enables them to produce thousands of eggs annually, which leads to rapid population growth and an expanding distribution"............... "Lake trout can consume cutthroat trout up to one-third their own size"............ "Although lake trout need energy-rich prey such as cutthroat trout to continue to grow, they can persist for years with minimal food resources due to their cold-blooded nature".........."These traits make it possible for lake trout to have drastic impacts on ecosystems outside their native range"..........."Given their long lives, ability to eat large prey, efficient predatory skills, and ability to persist on a variety of foods, lake trout not only deplete native species, but also persist at levels that keep native populations suppressed".............. "Thus, when lake trout were first caught in Yellowstone Lake in 1994, fishery professionals and park managers realized they had a serious problem".......... "In addition to killing cutthroat trout, lake trout could reduce the cutthroat trout’s food base, thereby making cutthroat trout recovery impossible until the lake trout population is suppressed"......…."Why lake trout were introduced into the lake is a mystery".............."Perhaps, biologists speculate, some anonymous angler wanted to diversify the fish population in the lake but didn't think through the consequences"............ "It's an example of bucket biology" ............."Lake trout are deepwater dwellers and inaccessible to the otters, ospreys, grizzly bears, and eagles that prey on easily caught, shallow-water-dwelling cutthroats"..................."Ten years ago, there were 50 nesting pairs of ospreys in the lake system area"............. "Today there are only three or four"..............."Thankfully, an extensive 9+ year effort to capture and kill non-native lake trout in Yellowstone Lake is showing progress with fewer of the invasive fish being found"..........."In 2018 so far, we've caught basically 155,000 lake trout, and that's 63,000 less than this time last year,reports Yellowstone National Park fisheries chief Todd Koel"............."That's huge and a real signal that this population is finally crashing"............. "It's what our science has predicted and the population modeling has predicted, and now we've finally started seeing it on the ground"............"It is estimated that another 14 years of intensive killing of Lake Trout will bring the "Cutties' back to ecosystem" carrying capacity functions"

https://lmtribune.com/outdoors/biologists-update-status-of-yellowstone-cutthroat-trout/article_210f3832-2168-5dca-9c95-3e1d34926d5c.html

Biologists update status of Yellowstone cutthroat trout

Officials explain ongoing efforts to help iconic fish species recover

An 18-inch cutthroat trout floats at the edge of LeHardy Rapids on the Yellowstone River in Yellowstone National Park in June. The fish were jumping the falls to swim upriver and spawn.

Billings Gazette/Brett French

BILLINGS, Mont. - In the late 1700s - as America's East Coast was being rapidly logged, trapped, fished, farmed and mined - scholars noticed a disturbing trend: native brook trout and Atlantic salmon populations were plummeting.

Cutthroat Native Range: Pacific Coast drainages from Prince William Sound, Alaska, to Eel River, northern California. Freshwater populations range through Rocky Mountains to Hudson Bay, Mississippi River, Great (including Lahontan, Bonneville, and Alvord basins), and Pacific basins from southern Alberta to Rio Grande drainage, New Mexico (Page and Burr 1991).

Lake Trout Native Range: Widely distributed from northern Canada and Alaska (missing in southern prairie provinces) south to New England and Great Lakes basin (Page and Burr 1991). In northwestern Montana, Lake Trout are native in Waterton Lake, Glenns Lake, Cosley Lake, and St. Mary Lake. (Snyder and Oswald 2005). In southwestern Montana, glacial relict populations of Lake Trout exist in Elk Lake and Twin Lake (Vincent 1963, Brown 1971, Synder and Oswald 2005).

The new nation's eventual answer to the problem was not to restore habitat or protect streams from rampant sources of pollution, as is often the case these days. Instead, in 1812, the Philadelphia Academy of Science created a curriculum in aquaculture - raising fish - at Cornell University. These newly trained fishery folk soon began moving, transplanting and experimenting with raising the first hatchery fish.

These lake trout were netted in Yellowstone Lake's Southeast Arm in 2015. Continued netting of lake trout has improved Yellowstone cutthroat trout numbers in the lake.

BRETT FRENCH, GAZETTE STAFF

In 1871, some of the same folks successfully established the U.S. Fish Commission. By the next year, scientists secured federal funds to begin raising fish in hatcheries to restock depleted populations.

"This is how we're going to save our native fish: we're going to use hatcheries," said Mike Ruggles, a Montana Fish, Wildlife and Parks fisheries biologist in Billings.

Trout talk

Ruggles was one of three fishery biologists to speak to a packed crowd of about 70 people at the April meeting of the Magic City Fly Fishers. The topic was Yellowstone cutthroat trout: what caused their populations to decline; what agencies are doing to protect and restore the fish; and what the future holds for the species. Also talking were Jason Rhoten, an FWP fisheries biologist based in Absarokee, and Phil Doepke, a Yellowstone National Park fisheries biologist.

 Cutthroats

"We wanted to cover more important conservation issues this year," said Lyle Courtnage, president of the fly fishers. "The native cutthroat trout has become a really important issue, not just for fisherman, but also the environment."

Ruggles led off the presentations by giving a vast historical overview of how Montana got to the point that native cutthroat trout habitat had been diminished by about 70 percent since the westslope cutthroat trout was first written about by Meriwether Lewis on June 13, 1805, at the Great Falls of the Missouri River. His description noted the distinct red slashes under the mouth that led to the fish's eventual name, the cutthroat.

Diminished habitat

At one time, there were at least 13 distinct species of cutthroat trout spread across the West. The yellowfin cutthroat was native to the headwaters of the Arkansas River in Colorado before becoming extinct thanks to the introduction of non-native rainbow trout in the late 1800s.

That early era of raising hatchery fish to transplant non-natives led to the transportation of boxcar loads of brook trout, brown trout and rainbows across the West and eventually to Montana, Ruggles said. That's because by 1864 the state had already enacted fishing rules that limited catches to hook and line only, banning all netting and trapping, which had severely depleted once plentiful native fisheries.

"So what did we end up doing? We spread non-natives all over the place," he said.

It wouldn't be until 1968 that forward-thinking FWP fisheries biologists suggested the state study not stocking the Madison River as an experiment in encouraging a sustainable native trout population.

"That did not go well. There were death threats," Ruggles said. "But by the mid-1970s they found that the population not only did better, it was doing way better."

By 1987, however, some believed the focus on native fisheries had come too late. The U.S. Fish and Wildlife Service was petitioned to consider the Yellowstone cutthroat trout as eligible for listing as an endangered species. That petition was denied, but it also served as a wake-up call to agencies like FWP.

Big Sky cutts

Montana is home to two species of cutthroat trout: westslope, which mostly occupy waters west of the Continental Divide with the exception of the Missouri River drainage; and Yellowstone, which once had its stronghold in Yellowstone Lake.

Historically, Rhoten said Yellowstone cutthroat trout occupied 17,800 miles of stream. Now it's estimated they have been reduced to about 7,500 miles and that includes cutthroat trout that have interbred with rainbow trout. The pure, core conservation populations of Yellowstone cutthroat occupy about 4,800 miles of stream.

Rhoten said one of the main reasons for protecting the fish is its importance to the food web of the region. Cutthroat trout feed species like grizzly and black bears, eagles and hawks.

"Everything is tied together," he said. "If the fish is not there, something down the line may suffer."

So since 2011, Montana Fish, Wildlife and Parks has completed 280 conservation projects just for Yellowstone cutthroat trout - things like improving connectivity and habitat, increasing streamflows and the more controversial removal of non-natives through poisoning so that natives can be restocked.

The upper Boulder River, Shields River, Soda Butte Creek, Lower Deer Creek, Sage Creek and Crooked Creek are just some of the fisheries where FWP has worked to remove non-native trout and restock native cutthroat, often building or using natural barriers to ensure the native fish are never again threatened by non-native fishes.

The next target is the Buffalo Fork of Slough Creek, just north of Yellowstone National Park and a tributary to the Lamar River. Non-native rainbow trout living in the Buffalo Fork are threatening the downstream populations of native cutthroat trout.

Yellowstone Lake

Likewise, in what was once the stronghold of Yellowstone cutthroat trout, biologists are now working to return the fish to its historical dominance. Decimated by illegally introduced lake trout (first documented in 1994) that can eat about 42 cutthroat a year, the cutthroat population has nosedived.

In Clear Creek, one of the major spawning tributaries for cutthroat trout that live in the lake, runs of fish dropped about 99 percent in three decades.

Netting has been the main means to remove lake trout from the water body. In 2017, more than 5,700 miles of gillnet were set, Doepke said, enough to reach from Billings to Washington, D.C., back to Oakland, Calif., and back to Billings. The nets were set by six different commercial boats working six days a week at a cost of about $1.5 million a season, which runs from May to September.

Last year, 397,000 lake trout were caught, but most of the fish were 8 to 12 inches long. Since 2013, when more than 400,000 pounds of biomass was netted, crews have seen that number fall to below 300,000.

"So we've knocked a lot of the large fish down," Doepke said.

That's important since it is the older fish that spawn. Lake trout typically reach sexual maturity between 5 to 10 years old. To further reduce the number of lake trout, the National Park Service has been experimenting with methods to kill eggs on spawning beds.

Killing eggs

The spawning beds have been found by implanting some lake trout with transceivers, allowing biologists to track them. Right now, there are between 200 and 400 lake trout that biologists are following. A dense array of receivers helps pinpoint spawning beds, most of which are located along the lake's southwest shoreline.

Using the technology, biologists have zeroed in on 14 different lake trout spawning beds that cover about 40 acres out of the lake's 89,000 total acres. Although burying the spawning beds in gravel, sucking up the eggs and electrocuting the nests has been tried, the most promising method of killing eggs has been to dump carcasses of the dead, netted lake trout on top of the spawning gravels.

The success of that work led to a cooperative project with the Bozeman Fish Technology Center to create a pellet, resembling rabbit food, that has a chemical resemblance to the rotting carcasses. In tests at the center, the pellets worked better than dead carcasses at killing lake trout eggs, Doepke said.

Yellowstone officials have established three metrics to measure the success of their lake trout removal effort: 1) gillnetting of 40 to 50 fish per net; 2) an increase in cutthroat angler success, which right now is below one per hour and the park would like to see it back around 1.5 to two fish per hour; 3) an increase in spawning cutthroat in nine tributary streams and the number of bears attracted to feed on those fish. Visual surveys used to count about 70 spawning fish, it's now around five.

"The three metrics are all below where we want them to be," Doepke said, but fisheries managers feel they have turned the corner.