The U.S. Fish and Wildlife Service has long said the population of Yellowstone cutthroat trout in Yellowstone Lake was abundant enough to keep the fish off of the federal endangered species list, but a new federal study casts serious doubts on the agency's ability to further rely on the lake's bounty.
The population of Yellowstone cutthroat trout in Yellowstone Lake, the fish's historic epicenter and stronghold, has decreased by 60 percent and their recovery "appears to be in peril," states a report released last month by National Park Service biologists.
"The cutthroat trout population size of this system was once considered to be in the millions," the report states. "However, current abundance indices suggest that only a fraction of that population exists today."
Published in the November issue of "Fisheries," the magazine of the American Fisheries Society, the report coincides with a U.S. Fish and Wildlife Service review to determine whether Yellowstone cutthroat should be listed as a threatened or endangered species under the Endangered Species Act.
Supporters of an ESA listing feel the report displays just how dire the situation has become since Yellowstone National Park is often regarded as the final refuge for a struggling species.
"We definitely think it is a wake-up call to fisheries biologists and agency managers to stop looking at Yellowstone National Park as the safety deposit box for Yellowstone cutthroat trout," said Scott Christensen, conservation organizer for the Greater Yellowstone Coalition.
The problem in Yellowstone Lake can be largely attributed to ravenous consumption of the lake's hallmark native cutthroat trout by lake trout, a large non-native piscivorous species that was discovered in Yellowstone Lake in 1994. An average mature lake trout in Yellowstone Lake will consume more than 40 mature cutthroat a year, according to the report.
Whirling disease and seven years of drought also have contributed to the trout's decline, and, outside the park, cutthroat face additional challenges like habitat loss from encroaching development, low water flows from irrigation, and competition from other non-native species, like rainbow, brook and brown trout.
Biologists believe Yellowstone cutthroat historically occupied more than 17,000 miles of habitat in Idaho, Wyoming, Montana and the extreme northern portions of Utah and Nevada. Their roots in the park date back about 10,000 years, when the last glaciers receded from the Yellowstone ecosystem, according to the report.
It's estimated that Yellowstone cutthroat trout now occupy less than 20 percent of their historic habitat.
The first calls to list the Yellowstone cutthroat, which is one of 14 subspecies of cutthroat native to the West, came in 1998. But in 2001, Fish and Wildlife, which oversees all ESA listings, claimed timely data to support a listing was lacking and federal protection wasn't warranted. Environmental groups sued, and in December 2004, a federal judge ordered Fish and Wildlife to reexamine the issue in what's known as a "status review."
That review, which will use public comment and scientific data, is currently ongoing and a decision from Fish and Wildlife on the ESA is scheduled to be released Feb. 14, 2006.
Lynn Kaeding, head of Fish and Wildlife's native fisheries management program in Bozeman, Mont., has been involved with fish-related ESA issues for 26 years. He will be a key player in the Fish and Wildlife's decision.
"By the first of the year, we have to have our decision made within the agency," he said.
To an outsider, it may seem obvious that the fish is in dire need of federal protection. But biologists like Kaeding aren't so sure.
While overall Yellowstone cutthroat numbers are down, they're on the rebound in some areas, specifically the Upper Snake River near Jackson, Wyo., and the South Fork of the Snake in eastern Idaho. Such cases will boost the overall condition of the subspecies, Kaeding said.
A decline in Yellowstone cutthroat numbers in the South Fork of the Snake River over the past decade also was largely due to an introduced species—the rainbow trout. Both rainbow and cutthroat trout spawn in the spring, which has led to crossbreeding. Until recently, the accelerating hybridization of the two species was threatening to eliminate genetically pure Yellowstone cutthroats from the South Fork, which is exactly what happened more than 50 years ago on the Henry's Fork—also known as the North Fork of the Snake River.
But a war on rainbows in the South Fork has put the Yellowstone cutthroat on a track to recovery.
In 2003, Fish and Game began encouraging anglers to harvest rainbows while returning all Yellowstone cutthroat to the water. The tactic has shown results—Yellowstone cutthroat numbers increased 27 percent last year, while the population of rainbows has dropped about 55 percent since 2003. According to Idaho Fish and Game, more than 5,000 rainbows were harvested in 2003 alone.
Higher spring flows from Palisades Reservoir, which feeds the South Fork about 45 miles east of Idaho Falls, have been tried the past two years to imitate natural runoff conditions that favor cutthroat. Cutthroat reproduction is 10 times greater than rainbow reproduction during high flows, according to Jim Fredericks, a regional fisheries manager with Idaho Fish and Game. Also, weirs that have been set up at the mouths of tributaries used by spawning cutthroats are designed to trap rainbows that are then transplanted to a kids' fishing pond south of Driggs.
Idaho Fish and Game officials were initially skeptical that catch-and-release minded anglers would harvest wild fish. But the program to enlist help in curbing rainbows has been largely embraced by anglers and outfitters who ply the South Fork.
"A lot of people have taken the message to heart and they'll do everything they can to save (the Yellowstone cutthroat)," said Matt Woodard, South Fork watershed manager for Trout Unlimited's Home Rivers Initiative in Idaho Falls. "I think we've come a long way in just a couple years, there's been a 180 degree shift in people's attitudes."
In Yellowstone Lake, efforts to curb the menacing population of lake trout has been far more challenging. As soon as the ice on the huge lake melts, officials with Yellowstone National Park's fisheries department begin gillnetting operations. In the last 10 years, they've netted more than 100,000 lake trout, including 36,000 between May and October of 2005.
Kaeding said evidence suggests lake trout were illegally transplanted to Yellowstone Lake from nearby Lewis Lake in the early 1980s. At that time, the cutthroats were on the rebound after decades of over-fishing that had caused their numbers to plummet. The lake trout just knocked them back down.
While the netting program has reduced the number of large lake trout, the overall population has still "grown dramatically," said Kaeding, who helped develop the netting program in the late-1990s when the U.S. Fish and Wildlife Service was still in charge of the park's fisheries.
"We've seen fewer big lake trout (in the past five years), but unfortunately there are a lot of younger but mature fish, there are lots of young lake trout coming on," he said. "The netting is not something we can let up on."
Additionally, whirling disease—caused by a parasite that attacks the nervous system, deforming and killing fish—and the prolonged drought also have taken a toll on Yellowstone cutthroat in the lake and upper Yellowstone River. Over the past several years, tributaries that flow into Yellowstone Lake and are used by spawning cutthroats have dried up by late summer.
In 1999, 2,363 cutthroats migrated up Bridge Creek, which flows into the lake's northwestern edge, to spawn. In 2004, only one fish arrived to spawn in Bridge Creek.
"A lot of those streams that flow in the lake have been quite dry during the cutthroat spawning season, and that, too, has undoubtedly had some effect on the reproduction and early life survival," Kaeding said. "I caution people about ascribing the (decline in cutthroat) to lake trout alone."
Pelican Creek—the lake's largest and most productive spawning tributary—provides the most dramatic example of the devastating effects of whirling disease on the lake's cutthroat population.
The exotic parasite that causes whirling disease in wild trout, Myxobolus cerebralis, was discovered in Yellowstone Lake in 1998, but by 2004, Yellowstone Superintendent Suzanne Lewis announced its rapid spread in the Pelican Creek drainage had forced the closure of the stream to fishing. Indications that the native cutthroat trout population had been virtually eliminated prompted the need to protect Pelican Creek's remnant population, she said.
"Our objectives are to protect the remaining cutthroat trout in Pelican Creek from stress and prevent potential movement of the destructive whirling disease parasite from Pelican Creek to other streams of Yellowstone," said Chief Fisheries Biologist Todd Koel.
Yet another factor that concerns park biologists about the dramatic decline of the cutthroat is the impact it could have on the Greater Yellowstone Ecosystem, as several animals, including pelicans, osprey otters, black and grizzly bears, feed on spawning cutthroat. Lake trout spawn in lakes and typically inhabit deeper depths, out of reach of predators. Therefore, they could never fill the cutthroat void in the food chain.
According to the "Flyfisher's Guide to Yellowstone National Park," the USFWS reported in the late 1990s that the total population of Yellowstone cutthroat in Yellowstone Lake exceeded 4 million.
But now, as the "Fisheries" magazine article stated, only a fraction of that population exists today. In 1999, anglers caught an average of 2.0 cutthroat per hour. That number dropped to 0.8 in 2004, suggesting the population has decreased by more than half since 1999 alone.
Kaeding said the report "doesn't paint a rosy picture for the Yellowstone cutthroat," but he said it also doesn't present any new groundbreaking information that would heighten the chances of a listing.
"It's not anything earth shattering," he said. "I don't think anyone who's been aware of what happened with Yellowstone cutthroat trout here in the lake found anything particularly surprising in the paper."
The Yellowstone cutthroat is the native trout of the upper Snake River and Yellowstone River basins. Listing it as a federally protected species could have far reaching impacts on water management in the region, including possible changes to "flushing flows" from upper Snake River dams that are used to help push salmon and steelhead smolts en route to the Pacific Ocean through four controversial dams on the lower Snake River. Express photo by Ken Retallic
