Part of a series of articles titled Yellowstone Science - Volume 25 Issue 1: Native Fish Conservation.
Article
YS 25-1-Shorts
Fly Fishing Volunteers Support Native Fish Conservation in Yellowstone
by Colleen R. Detjens, William Voigt, Joann Voigt, & Todd M. Koel
The Yellowstone Fly Fishing Volunteer Program was conceived in 2002 as a way Yellowstone’s biologists could acquire information about fish populations without having to travel to distant locations throughout the park and sample the populations themselves using electrofishing or other sophisticated gear. Yellowstone National Park contains an estimated 4,265 km (2,650 mi.) of streams and more than 150 lakes, many of which support native fish populations that could be monitored; however, emerging resource concerns such as the invasion of non-native lake trout and whirling disease occupy progressively more time and financial resources of the park’s fisheries program. As a way to sample fish populations and address fisheries issues park biologists would otherwise not be able to do, the fly fishing volunteers use angling to gather and archive information and biological samples.
Each year, a list of projects is developed by park biologists, so volunteers can focus their efforts. In its early years, the program was led by Timothy Bywater, an avid fly fisher and supporter of Yellowstone’s native fish conservation program. William Voigt, also an avid fly fisher, joined the program in 2004 and eventually took over the job of program coordinator. Over the years, hundreds of fly fishers have volunteered with the program. These volunteers are important to the conservation of Yellowstone’s native fish in a myriad of ways. They provide data and collect samples in important project areas, as well as in areas we may not know much about. They also play an important role in communicating with the public. They interact with tourists and other fly fishers on a regular basis and are able to discuss important topics, such as park fishing regulations, the reasoning behind some of the more controversial restoration projects, and why native fish are an important resource in Yellowstone.
How They Contribute
The volunteer fly fishing program attracts anglers from all across the United States, many of whom choose to come back year after year. Since the start of the program, 914 volunteers have contributed almost 23,000 hours to support native fish conservation in Yellowstone (figure 1). Of the 914 volunteers, 309 have returned for more than one season. These volunteers perform a wide range of duties in assisting the Yellowstone fisheries program, providing everything from logistical support to extensive sample collection. Collectively, program volunteers have sampled 7,000 fish since 2002 via angling. Data collected from each fish is recorded on datasheets and archived in computer databases. Along with fish lengths, weights, condition, and other basic data, volunteers also collect biological samples to be later processed in a laboratory. For example, volunteers have been integral in collecting genetic samples from various locations. Most notably, the samples they collected from the Lamar River and Slough and Soda Butte creeks aided park managers in understanding the extent of cutthroat trout hybridization in these drainages, thus contributing to subsequent management decisions. Other genetic sampling efforts across the park have been used to confirm or dismiss the presence of hybridization in a population, again aiding park biologists in management decisions. Between 2007 and 2014, volunteers collected 263 genetic samples from the Slough Creek drainage alone.The volunteer fly fishers also provide invaluable support for fish tagging projects, such as those conducted on the Gibbon and Lamar rivers. These projects provide information on the life history and movement of species, such as Arctic grayling (Gibbon River) and rainbow trout and cutthroat rainbow trout hybrids (Lamar River and Slough and Soda Butte creeks). The collection of fish large enough to tag and for insertion of the tag itself can be an arduous process. During 2015, the volunteer fly fishing program caught and tagged approximately 220 fish in the Lamar River system. With the help of the volunteer program, biologists and collaborating graduate students were able to work more efficiently and effectively, ultimately providing managers with the best data possible.
Since the start of the program, volunteers have also assisted with several other projects, including removal of non-native species, evaluation of fish barrier efficacy and success, a study to determine injury and mortality rates when using barbed versus barbless hooks, surveys to determine species composition, and logistical support for large multi-agency projects.
Their Role with the Public
In addition to providing valuable data, samples, and assistance to the fisheries program, volunteer fly fishers play an important role with the public. The program itself gives dedicated anglers a chance to contribute to fish conservation efforts in a positive way. Through their role as volunteers, they are able to positively interact with the public and demonstrate their passion for native fish and the importance of protecting these species. Volunteer fly fishers promote an understanding of the park’s fishing policies and regulations, and generate awareness of the current issues facing Yellowstone’s native fish. Passionate and informed supporters such as these are an important contribution to the success of native fish conservation in Yellowstone.Shared Experiences
Over the years the Yellowstone Fly Fishing Volunteer Program has been in existence, there have been many experiences shared among the coordinators and participating volunteers. Notes are taken by the volunteer coordinator during field outings with volunteers; below are three examples of those notes.Cache Creek
“Today, August 11, 2005, we hiked 3 miles up the Lamar River Trail to collect genetic samples from the Cutthroat Trout in Cache Creek. It started bright and sunny but as the afternoon progressed many thunderstorms passed around us. We fished a half mile of the stream and took fin clips and scale samples from 20 fish. There wasn’t any hatch but fish rose to our hopper and caddis patterns. With more storms threatening, we headed back down the trail to the parking lot. It was obvious that it had rained hard along the Soda Butte Creek because the trail and the creek were muddy.
As we loaded our gear into our van, two park ranger cars blocked us in and the rangers demanded to see our licenses and fish. They had a report of six people catching fish and keeping them in yellow buckets up on Cache Creek. After some explanation of the program, one of the rangers remembered fishing with Tim Bywater the previous year. One of our volunteers was quite a large lad with a voracious appetite and had brought half of a pork roast in his pack for lunch. We teased him that one of the rangers was eyeing him up to decide how to take him down if he was to run. We all chuckled.
The Lamar valley is becoming one of our favorite places in the park. The broad vistas of the valley are quite spectacular! We saw bison, pronghorns, and a coyote as well as a kestrel hunting in the meadows. It was great day!”
High Lake
“High Lake was the first body of water recently reclaimed for West Slope [sic] Cutthroat Trout. Now, two years later Colleen Detjens (see page 27) in August 2009, we were going to High Lake for two days of fishing for West Slope [sic] Cutthroat Trout. This was our first horse-packing trip in the park and we all were excited. Our volunteers were so eager that they willingly rented their own horses and brought their own supplies and equipment. We were to weigh and measure every fish we caught. We were also to record whether the adipose fin had been clipped. That would indicate that they had been stocked as fingerlings. If the adipose fin was intact, they had hatched from egg boxes put in the spring feeding the lake or from natural reproduction.
It was a ten mile ride up to the lake on top of the mountain very close to the northwest border of the park. We set up camp and then started fishing. We caught many fish in the 11 to 11 ¾ inch range with their adipose fin clipped; so many so that a competition was occurring to see who would catch the first 12 inch fish. However, several smaller fish were caught with their fins intact. The lake and its fish seemed to be doing well; we caught 67 fish over the course of two days.
The days were pleasant, but the nights were very cold. Hot chocolate was welcome in the morning. And no one caught that 12 inch fish.”
Pelican Creek
“Our destination in July 2011, was Pelican Creek. We hiked 1.5 miles up the trail to the creek with 2 volunteers. The creek had been closed for seven years because of the discovery of whirling disease and had just been reopened. We were to sample the Yellowstone Cutthroat trout population to see how their recovery was progressing. During the course of the sunny day, we saw a few elk, a grizzly bear, a small herd of bison, a Trumpeter swan, and a Swainson’s hawk. Fishing was slow, but we caught two 19” cutthroat trout obviously up from the lake to spawn. On our way out, one of our volunteers turned to us, and even though he didn’t catch any fish, he said, ‘Thank you. You took me to a beautiful place I would never have seen on my own.’
Several days later we went back up Pelican Creek with writer Nate Schweber and caught several 5-6 inch healthy-looking Yellowstone Cutthroat trout. Schweber dedicated the final chapter of his book, Fly Fishing Yellowstone National Park, to the recovery of Pelican Creek.”
from Yellowstone Science 25(1)
There were more than 4 million visits to Yellowstone National Park in 2016, all drawn by the same want—to better know the wonders of our natural world. And what better place to meet nature’s best ambassadors? Yellowstone is well-known for its animals, such as grizzly bears, bison, wolves, elk, and eagles. Yet among these ambassadors, one species stands out as the best: trout. Hear me out, non-anglers. Of all the game animals in Yellowstone, the only ones people are welcome to make a physical connection with are trout (I’m including in my thesis brook trout and lake trout, technically char, and also their cousins, Arctic grayling and mountain whitefish).
Think of the reciprocation in that ceremony. A person wrangles, touches, lifts, and studies a wild animal, from the mercurial colors of its speckled sides to the obsidian triangles in its eyes. If the trout is non-native, under the right circumstances the angler can eat it—a communion with Yellowstone. Native trout, however, always must be let go. Then each release becomes a human lesson in the magnanimity of restraint, a concept with wide-reaching implications for our changing earth.
But for this ceremony to happen, for the lessons to be learned, trout must first be preserved. Native trout are the most imperiled. For their sake, Yellowstone officials have taken some of the bravest and most proactive steps in conservation history.
When Yellowstone cutthroat trout in Yellowstone Lake dropped to dangerously low levels in the mid-20th century, the park set strict angler limits. When these native cutthroats were killed in even more devastating numbers by illegally-introduced lake trout in the early 21st century, officials began using boats to net lake trout. To-date, this ambitious netting campaign has removed more than two million of the non-natives. Slowly, native cutthroats are returning.
On the sunset side of the Continental Divide, Yellowstone biologists led by Todd Koel recently restored populations of another native trout gone for nearly a century— westslope cutthroat. Ambitious hikers can climb to High Lake and find westslope cutthroats cruising teal waters deep in the Gallatin Range. Cyclists can pedal to Goose Lake, a short ride from steaming Midway Geyser Basin, to find westslope cutthroat. Soon, people will be able to once again catch westslope cutthroat and sailfinned Arctic grayling in Grayling Creek. That’s welcome news for anglers, for the rare grayling, and for the veracity of maps.
Recently, Yellowstone set rules requiring anglers to automatically kill non-native trout in certain imperiled waters. While controversial, the decision sent a powerful message throughout the National Park Service about the urgency of protecting native trout and, by extension, all animals that coexist with them. By setting this precedent, Yellowstone saved steelhead in Washington’s Olympic National Park, bull trout in Montana’s Glacier National Park, Bonneville cutthroat trout in Nevada’s Great Basin National Park, and brook trout in North Carolina and Tennessee’s Great Smoky Mountains National Park.
One million years of mankind’s exploratory and intellectual effort led to the creation of Yellowstone National Park—the world’s first national park, the best idea from the best country in history. The next million years will be shaped for the better if Yellowstone remains a place where people can catch trout, and trout can catch people.
Nate Schweber is the author of “Fly Fishing in Yellowstone National Park: An Insider’s Guide to the 50 Best Places.” A freelance journalist, his work has appeared in the New York Times, Al Jazeera America, and Montana Quarterly. Born and raised in Missoula, Montana, he now lives in Brooklyn, New York. Nate spent the summers of 1997 and 2011 working in Yellowstone.
Where People Can Catch Trout, & Trout Can Catch People
by Nate Schweber
There were more than 4 million visits to Yellowstone National Park in 2016, all drawn by the same want—to better know the wonders of our natural world. And what better place to meet nature’s best ambassadors? Yellowstone is well-known for its animals, such as grizzly bears, bison, wolves, elk, and eagles. Yet among these ambassadors, one species stands out as the best: trout. Hear me out, non-anglers. Of all the game animals in Yellowstone, the only ones people are welcome to make a physical connection with are trout (I’m including in my thesis brook trout and lake trout, technically char, and also their cousins, Arctic grayling and mountain whitefish).
Think of the reciprocation in that ceremony. A person wrangles, touches, lifts, and studies a wild animal, from the mercurial colors of its speckled sides to the obsidian triangles in its eyes. If the trout is non-native, under the right circumstances the angler can eat it—a communion with Yellowstone. Native trout, however, always must be let go. Then each release becomes a human lesson in the magnanimity of restraint, a concept with wide-reaching implications for our changing earth.
But for this ceremony to happen, for the lessons to be learned, trout must first be preserved. Native trout are the most imperiled. For their sake, Yellowstone officials have taken some of the bravest and most proactive steps in conservation history.
When Yellowstone cutthroat trout in Yellowstone Lake dropped to dangerously low levels in the mid-20th century, the park set strict angler limits. When these native cutthroats were killed in even more devastating numbers by illegally-introduced lake trout in the early 21st century, officials began using boats to net lake trout. To-date, this ambitious netting campaign has removed more than two million of the non-natives. Slowly, native cutthroats are returning.
On the sunset side of the Continental Divide, Yellowstone biologists led by Todd Koel recently restored populations of another native trout gone for nearly a century— westslope cutthroat. Ambitious hikers can climb to High Lake and find westslope cutthroats cruising teal waters deep in the Gallatin Range. Cyclists can pedal to Goose Lake, a short ride from steaming Midway Geyser Basin, to find westslope cutthroat. Soon, people will be able to once again catch westslope cutthroat and sailfinned Arctic grayling in Grayling Creek. That’s welcome news for anglers, for the rare grayling, and for the veracity of maps.
Recently, Yellowstone set rules requiring anglers to automatically kill non-native trout in certain imperiled waters. While controversial, the decision sent a powerful message throughout the National Park Service about the urgency of protecting native trout and, by extension, all animals that coexist with them. By setting this precedent, Yellowstone saved steelhead in Washington’s Olympic National Park, bull trout in Montana’s Glacier National Park, Bonneville cutthroat trout in Nevada’s Great Basin National Park, and brook trout in North Carolina and Tennessee’s Great Smoky Mountains National Park.
One million years of mankind’s exploratory and intellectual effort led to the creation of Yellowstone National Park—the world’s first national park, the best idea from the best country in history. The next million years will be shaped for the better if Yellowstone remains a place where people can catch trout, and trout can catch people.
Nate Schweber is the author of “Fly Fishing in Yellowstone National Park: An Insider’s Guide to the 50 Best Places.” A freelance journalist, his work has appeared in the New York Times, Al Jazeera America, and Montana Quarterly. Born and raised in Missoula, Montana, he now lives in Brooklyn, New York. Nate spent the summers of 1997 and 2011 working in Yellowstone.
Birds & Mammals that Consume Yellowstone Cutthroat Trout in Yellowstone Lake and Its Tributaries
by Daniel J. Bergum, Kerry A. Gunther, & Lisa M. Baril
Yellowstone Lake in Yellowstone National Park (YNP) contains the largest inland population of Yellowstone cutthroat trout (Oncorhynchus clarkii bouvieri) in North America (Behnke and Tomelleri 2002). Historically, these native trout provided food for a variety of wildlife. In 1994, however, park managers discovered non-native lake trout (Salvelinus namaycush) had been surreptitiously introduced into the lake. Their numbers increased rapidly and, in turn, their piscivorous (i.e., fish eating) food habits became a significant threat to the Yellowstone cutthroat trout population (Koel et al. 2005). In addition, the non-native parasite (Myxobolus cerebralis) that causes whirling disease, a significant cause of juvenile mortality, was discovered in tributaries to Yellowstone Lake during 1998 (Koel et al. 2006). Plus, a recent period of drought reduced the survival and recruitment of juvenile cutthroat trout (Koel et al. 2005). These combined effects caused a 90% decline in the cutthroat trout population in Yellowstone Lake (Koel et al. 2005). Lake trout are not a suitable ecological substitute for cutthroat trout in the Yellowstone Lake system.
Lake trout inhabit deeper waters and, unlike cutthroat trout, do not move into tributary streams to spawn; therefore, lake trout are inaccessible to many avian and terrestrial predators (Koel et al. 2005). Although lake trout do move into shallow waters of the lake to spawn, they often spawn at night which makes them unavailable to shallow water avian predators with diurnal habits. Spawning cutthroat trout migrate throughout the day and night (Gresswell 2011), which makes them vulnerable to nocturnal, crepuscular, and diurnal shallow water predators.
The decline in cutthroat trout could have negative consequences on the reproduction and survival of birds and mammals that consume them in the Yellowstone Lake watershed. We reviewed available literature to determine which predator and scavenger species are known to prey on or scavenge cutthroat trout in Yellowstone Lake or its tributaries and, as a result, might be adversely affected by the decline in cutthroat trout. Our literature review included all 221 bird and 67 mammal species known to inhabit YNP (see www.nps. gov/yell/learn/nature/ to view species checklists for the park).
We identified 20 species, including 16 birds and 4 mammals, which prey on or scavenge cutthroat trout in Yellowstone Lake or its tributaries (table 1). The bird species known to prey on cutthroat trout include osprey, American white pelican, Caspian tern, double-crested cormorant, belted kingfisher, common merganser, eared grebe, great blue heron, California gull, bald eagle, common loon, American dipper, Barrow’s goldeneye, bufflehead, common raven, and great horned owl. In addition, four species of mammals—American black bear, grizzly bear, mink, and river otter—have been documented preying on cutthroat trout in Yellowstone Lake or its tributaries. The cutthroat trout decline has likely affected each of these species differently, due to their varied feeding habits and lifestyles.
Although the decline in cutthroat trout in Yellowstone Lake probably has caused some disruption in the food supply for all 20 of these species, the greatest impacts have been incurred by five species: osprey, American white pelican, Caspian tern, double-crested cormorant, and river otter. Nesting success for ospreys, cormorants, American white pelicans, and Caspian terns has decreased over the last 20 years, coinciding with the period of cutthroat trout decline (Smith et al. 2012, 2013, Baril et al. 2013). The only known nesting area for Caspian terns, American white pelicans, and dou ble-crested cormorants in YNP is on the Molly Islands in the Southeast Arm of Yellowstone Lake. The reduced availability of cutthroat trout and lack of an alternative prey source means these species have to travel farther to find food, which in turn likely reduces nesting success and increases the energetic costs of foraging with possible consequences to survival.
The river otter has also incurred significant impacts. Crait and Ben-David (2006) found little evidence otters could switch to feeding on introduced lake trout as an alternative prey to cutthroat trout. Lake trout are abundant and lipid rich, but are generally found in deep water beyond the foraging depth range of otters (Ben-David et al. 2000). Although longnose suckers (Catostomus catostomus) are a slow moving species, grow to a large size, and are obligate stream spawners (Brown and Graham 1954), they are less abundant (Stapp and Hayward 2002) and of lower energetic value (Ruzycki et al. 2003) than cutthroat trout. Therefore, longnose suckers are not an equivalent alternative prey for otters (Crait and Ben-David 2006). The decline in the cutthroat trout population in combination with the inaccessibility of lake trout and lower abundance and energetic return of alternative prey is expected to reduce the population density of otters in Yellowstone Lake (Crait and Ben-David 2006).
Grizzly bears, black bears, and bald eagles with home ranges around Yellowstone Lake have exhibited dietary flexibility and switched to other foods, limiting the potential nutritional stress caused by the loss of cutthroat trout as a food item. Bears are opportunistic omnivore generalists that feed on many species of plants, fungi, mammals, insects, birds, and fish. Fortin et al. (2013) found evidence that bears with home ranges adjacent to Yellowstone Lake may now be preying more on elk calves during the time period when they used to fish for cutthroat trout. Bald eagles appear to have compensated for the decrease in cutthroat trout by preying more on waterfowl (Baril et al. 2013). Like bears, the California gull and common raven are also opportunistic omnivore generalists (Davenport 1974, McEneaney 2002) capable of eating many different foods, thereby minimizing the impacts of the cutthroat trout decline.
In the past, cutthroat trout comprised a large portion of the diets of common loons, common mergansers, eared grebes, great blue herons, and belted kingfishers around Yellowstone Lake (Davenport 1974). However, except for the common loon, the reproduction and nesting success of these species has not been monitored. As a result, the impacts of cutthroat trout decline on these species are not known. The number of adult common loons observed in YNP appears stable, although nesting pairs and fledglings have decreased since 1987 (Smith et al. 2012). As of 2014, one-third of the park’s 29 loons nested and foraged on Yellowstone Lake. Loons in YNP are of special concern since they represent nearly 64% of all loons in Wyoming and are isolated from other populations by more than 200 miles (Evers et al. 2013). Cutthroat trout comprise a minor component of the diets of mink (Lariviere 2003, Melquist et al. 1981), American dippers, Barrow’s goldeneyes, buffleheads (Davenport 1974), common ravens, and great horned owls (McEneaney 2002). Therefore, the impact of the cutthroat trout decline on the reproduction and survival of these species is likely minimal.
The cutthroat trout is an iconic and important species due to its place in the food web in Yellowstone and the Greater Yellowstone Ecosystem. Park managers are attempting to restore cutthroat trout in Yellowstone Lake and its tributaries through an aggressive lake trout removal program. If this program results in a significant long-term reduction in predatory lake trout, native cutthroat trout may reestablish at higher numbers in Yellowstone Lake and its tributary streams, and once again become an important dietary item for the birds and mammals that feed on this resource in the Yellowstone Lake watershed.
For an expanded version of table 1 which includes all known, suspected, and possible species that consume Yellowstone cutthroat trout, please visit go.nps. gov/who_eats_YCT
Literature Cited
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Baril, L.M., D.W. Smith, T. Drummer, and T.M. Koel. 2013. Implications of cutthroat trout declines for breeding ospreys and bald eagles at Yellowstone Lake. Journal of Raptor Research 47:234-245.
Brown, C.J.D., and R.J. Graham. 1954. Observations on the longnose sucker in Yellowstone Lake. Transactions of the American Fisheries Society 83:38-46.
Crait, J.R., and M. Ben-David. 2006. River otters in Yellowstone Lake depend on a declining cutthroat trout population. Journal of Mammalogy 87:485-494.
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Fortin, J.K., C.C. Schwartz, K.A. Gunther, J.E. Teisberg, M.A. Haroldson, M.A. Evans, and C.T. Robbins. 2013. Dietary adjustability of grizzly bears and American black bears in Yellowstone National Park. Journal of Wildlife Management 77:270- 281.
Gresswell, R.E. 2011. Biology, status, and management of the Yellowstone cutthroat trout. North American Journal of Fisheries Management 31:782-812.
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Heinrich, B. 1999. Mind of the raven: investigations and adventures with wolf-birds. Harper-Collins Publishers, New York, New York, USA.
Koel, T.M., P.E. Bigelow, P.D. Doepke, B.D. Ertel, and D.L. Mahony. 2005. Nonnative lake trout results in Yellowstone cutthroat trout decline and impacts to bears and anglers. Fisheries 30:10-19.
Koel, T.M., D.L. Mahony, K.L. Kinnan, C. Rasmussen, C. Hudson, S. Murcia, and B.L. Kerans. 2006. Myxobolus cerebralis in native cutthroat trout of the Yellowstone Lake ecosystem. Journal of Aquatic Animal Health 18:157-175.
Lariviere, S. 2003. Mink (Mustela vison). Pages 662-671 in G.A. Feldhamer, B.C. Thompson, and J.A. Chapman, editors. Wild mammals of North America: biology, management, and conservation. Johns Hopkins University Press, Baltimore, Maryland, USA.
McEneaney, T. 2002. Piscivorous birds of Yellowstone Lake: their history, ecology, and status. Pages 121-134 in R.J. Anderson and D. Harmon, editors. Yellowstone Lake: hotbed of chaos or reservoir of resilience? Proceedings of the 6th Biennial Scientific Conference on the Greater Yellowstone Ecosystem. National Park Service, Yellowstone National Park, Wyoming, USA.
Melquist, W.E., J.S. Whitman, and M.G. Hornocker. 1981. Resource partitioning and coexistence of sympatric mink and river otter populations. Pages 187-220 in J.A. Chapman and D. Pursley, editors. Proceedings of the worldwide furbearer conference. Frostburg, Maryland, USA.
Reinhart, D.P., and D.J. Mattson. 1990. Bear use of cutthroat trout spawning streams in Yellowstone National Park. International Conference on Bear Research and Management 8:343- 350.
Ruzycki, J.R., D.A. Beauchamp, and D.L. Yule. 2003. Effects of introduced lake trout on native cutthroat trout in Yellowstone Lake. Ecological Applications 13:23-37.
Smith, D.W., L. Baril, A. Boyd, D. Haines, and L. Strait. 2013. Yellowstone National Park bird monitoring report 2013. YCR- 2013-1. National Park Service, Yellowstone Center for Resources, Yellowstone National Park, Wyoming, USA.
Smith, D.W., L. Baril, A. Boyd, D. Haines, and L. Strait. 2012. Yellowstone bird program 2012 annual report. YCR-2012-01. National Park Service, Yellowstone Center for Resources, Yellowstone National Park, Wyoming, USA.
Stapp, P., and G.D. Hayward. 2002. Estimates of predator consumption of Yellowstone cutthroat trout (Oncorhynchus clarki bouveri) in Yellowstone Lake. Journal of Freshwater Ecology 17:319-329.
Swenson, J.E., K.L. Alt, and R.L. Eng. 1986. Ecology of bald eagles in the Greater Yellowstone Ecosystem. Wildlife Monographs 95:1-46. Swenson, J.E. 1978. Prey and foraging behavior of ospreys on Yellowstone Lake, Wyoming. Journal of Wildlife Management 42:87-90.
Varley, J.D., and P. Schullery. 1983. Freshwater wilderness, Yellowstone fishes and their world. The Yellowstone Library and Museum Association, Yellowstone National Park, Wyoming, USA.
Dan Bergum first visited Yellowstone during the 1988 fires as a boy, leading him to pursue a BS in Ecology at the University of Minnesota at Mankato. He has worked as a biologist for the past 12 years and a Bear Management Technician in Yellowstone National Park for the past five. Dan, his wife Karin, and two sons Colter and Theodore, spend their time outdoors exploring the mountains of Wyoming.
Last updated: November 14, 2023