Aquatic Invasive Species in Yellowstone National Park
Fiona Hood & Kate McKeown
Summary:
Yellowstone National Park’s aquatic systems have undergone numerous alterations since the park’s inception in 1872. The fishless waters were stocked with non-native trout species to increase opportunities for recreational fishing. Additionally, visitors have unintentionally introduced other aquatic invasive species, including non-native snails and a parasite. In the following decades, awareness of the negative impacts of these invasive species arose, and mitigative measures were implemented. Presently, efforts continue to save the native Yellowstone cutthroat trout, which is struggling due to competition and hybridization with the invasive trout species. Impacts from the loss of native trout have already spread beyond Yellowstone’s waterways, affecting semi-aquatic species, such as river otters and waterfowl as well as terrestrial species, including grizzly bears and black bears. Yellowstone National Park’s aquatic systems are susceptible to climate change, which will act as another challenge in the efforts to control the invasive species. With persistent, ongoing intervention, it is possible to decrease the spread of invasive trout species and restore the Yellowstone cutthroat trout populations to their historic numbers.
Genealogy
Following glacial melt approximately 10,000-8,000 years before present, twelve species of native fish populated the Yellowstone region (National Park Service, 2019), including Yellowstone cutthroat trout (Oncorhynchus clarkii bouvieri), which migrated from a refugia in Idaho via Two Ocean Pass (Kaeding, 2012) and Arctic grayling (Thymallus arcticus) which migrated from the Upper Missouri River (Stamford and Taylor, 2004). Because of natural barriers, roughly 40% of Yellowstone’s waters, including Lewis Lake, Shoshone Lake, and part of Firehole River lacked fish when the park was established in 1872 (Figure 3) (National Park Service, 2019). To provide additional recreational fishing areas in the newly instituted park, managers stocked the fishless lakes with non-native brook trout (Salvelinus fontinalis), brown trout (Salmo trutta), lake trout (Salvelinus namaycush), and rainbow trout (Oncorhynchus mykiss) (Figure 4). As the water bodies are connected, the non-native trout, especially lake trout, dispersed beyond Lewis and Shoshone lakes to Heart Lake and finally Yellowstone Lake in the late 1980s (Munro et al., 2005). As early as the 1920s, park officials began to realize that the non-native trout were outcompeting cutthroat trout for food and habitat and were hybridizing with the native species (National Park Service, 2019). Therefore, park managers discontinued the stocking of non-native species in the 1930s but continued to stock cutthroat trout from Yellowstone Lake to areas within and beyond the cutthroat’s native range into the 1950s (National Park Service, 2019).
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Despite efforts to increase the number of cutthroat trout, the negative impacts of the invasive fish species were exacerbated by overfishing. In the 1960s, a report indicated the rapid overfishing was leading to an increase in growth rate of cutthroat trout and a decrease in the percentage of mature cutthroat trout in Yellowstone Lake (Bulkley, 1961). Bulkley (1961) stated that “if the [number of cutthroat trout caught annually] continues to increase at the present rate, it may become excessive within the next few years” (pp. 23). Bulkley was correct. Cutthroat trout became more and more scarce in the park, and regulations established in 2001 required all caught native fish to be released and all caught rainbow trout, brook trout, lake trout, and cutthroat/ rainbow trout hybrids to be killed (National Park Service, 2018).
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Additional threats to native fish species include Myxobolus cerebralis, a European parasite which causes whirling disease, and two snail species: New Zealand mud snails (Potamopyrgus antipodarum), and Red-rimmed melania (Melanoides tuberculatus). Myxobolus cerebralis feeds on fish cartilage, causing infection which can result in a blackened tail and skeletal deformities. The deformities cause the fish to swim in a whirling pattern, giving rise to the name “whirling disease”. The parasite was first detected in Yellowstone in 1998 and is presumed to have arrived in the US in frozen fish products from Europe. While lake trout and Arctic grayling are immune to the disease and brown trout are resistant, cutthroat trout have no defense mechanism to ward off the parasite (National Park Service, 2017b).
New Zealand mud snails and Red-rimmed melania pose an indirect effect on native fish species. These snails consume a large quantity of algae, making it unavailable to invertebrates which are the main food source of young trout and several bird species. The mud snails were first detected in 1994 and the melania were only discovered in 2009. It is likely they were introduced in the 1930s as part of the aquarium trade (National Park Service, 2017a).
New Zealand mud snails and Red-rimmed melania pose an indirect effect on native fish species. These snails consume a large quantity of algae, making it unavailable to invertebrates which are the main food source of young trout and several bird species. The mud snails were first detected in 1994 and the melania were only discovered in 2009. It is likely they were introduced in the 1930s as part of the aquarium trade (National Park Service, 2017a).
Present Conditions
There have been a number of adverse effects surrounding the introduction of non-native fish to Yellowstone National Park. Several scientific review panels advised that suppression of lake trout was necessary in order to revive the cutthroat trout population. In 2012, removal efforts were increased to decrease the lake trout population growth rate and a total of 2.3 million lake trout were removed by the end of 2016 (Bigelow, et al., 2017). Gill nets have been the primary tool for capturing lake trout, however, other catchment methods include live-entrapment nets, recreational fishing, and advanced technology for killing lake trout eggs (Gresswell, et al. 2015). The future of cutthroat trout in the park seems positive, as non-native fish populations have declined significantly with intensified suppression efforts (Bigelow, et al., 2017).
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Yellowstone cutthroat trout are a keystone species in Yellowstone National Park, as four mammal species and 16 bird species consume them (Syslo, 2015). Their decline caused major cascading effects throughout the ecosystem (Figure 6), extending to land-dwelling organisms such as black bears (Ursus americanus) and grizzly bears (Ursus arctos). In the early 1950s, multiple bear species within Yellowstone relied heavily on tributaries that contained cutthroat trout during the spawning seasons. Studies compared estimates from 1997 to the number of bears visiting spawning streams in recent years, and noted a decrease of 63% (Koel, et al., 2017). To supplement their diet, the grizzlies and black bears increased predation on elk calves (Koel, et al., 2017). Some species, however, are not opportunistic feeders, and face much larger impacts, such as the river otter (Lontra canadensis). River otters are restricted to specific areas as they lack mobility and are unable to switch from a fish-based diet (Crait & Ben-David, 2006). Otters were required to supplement their diets with less nutritive alternatives, such as non-native longnose suckers (Catostomus catostomus) and amphibians. Although estimates of otter abundance do not exist prior to the 2000s, many researchers suggest their populations have declined in relation to the cutthroat trout (Koel, et al., 2017).
Bald eagles (Haliaeetus leucocephalus) are another species directly affected by the decline in cutthroat populations. A number of eagles built their nests near Yellowstone lakes and were unable to relocate when the decline in cutthroat trout began. As a result, eagle nest productivity decline and predation on other bird species increased (Wilkinson, 2018). This lead to a population decline in a number of migratory bird species found within Yellowstone, such as California gulls (Larus californicus), American white pelicans (Pelecanus erythrorhynchos), Canadian geese (Branta canadensis), and many more.
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The social response to these events has be vast. A nonprofit program created by locals called “Save the Yellowstone Cutthroat trout” (Yellowstone Forever, n.d.), aims to preserve native fish populations in Yellowstone. A number of management strategies have been integrated based on expert scientific panel reviews, to ensure a decline in non-native fish species and an increase in cutthroat trout populations. These actions mainly involve lake trout suppression netting, which uses specialty nets to target the deeper water where lake trout reside. Furthermore, the release of native fish species is still required by park regulations, and 99.9% of them are reported released (National Park Service, 2010). Alongside trying to reduce non-native species, management strategies such as the Native Fish Conservation Plan have been designed in order to increase cutthroat trout populations. The plan consists of recovering Yellowstone cutthroat trout abundance to that documented before non-native invasion, restoring genetically pure cutthroat trout, and maintaining access to historical spawning tributaries for native fish (Koel, et al. 2015).
Future Trajectory
The introduction of non-native species has not only changed the biological trajectory of Yellowstone National Park, but has also shifted human values from recreation to conservation. Approximately 50,000 of the park’s four million visitors purchase a fishing licence each year (National Park Service, 2018), and learn to distinguish between the non-native species which they can keep and the native species which must be released. Furthermore, the park has instituted a conservation plan which relies on volunteer angler reports to estimate the number of cutthroat trout and non-native trout in the lakes (National Park Service, 2015). The conservation plan is supported by the “Save the Yellowstone Cutthroat trout” organization (Yellowstone Forever, n.d.) and proposes practical solutions to reduce the invasive trout populations.
These conservation efforts are crucial as population models developed by McIntyre (1995) and Stapp and Hayward (2002) predict that if lake trout persist without the current management methods, they could eliminate 60-70% of the Yellowstone cutthroat trout population by 2100 (Crait & Ben-David, 2006). However, with intensive management, including suction dredging of lake trout embryo habitat and electro-shocking lake trout embryos, the lake trout population could be suppressed by 2025 (Bigelow, et al., 2017). This is especially feasible since the lake trout invasion is contained to Yellowstone, as there are no other interconnecting lakes or waterways (Koel, et al., 2017). In a similar undertaking, Pacas and Taylor (2015) used gill nets and electrofishing over a 5-year period to eliminate non-native brook trout from two subalpine lakes in Banff National Park. They attribute the success of their project to the magnitude of their efforts, which provides hope that similar success could be had in Yellowstone National Park.
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Climate change is also likely to alter the trajectory of the park. Recent trends in climate models show that temperature rise and bark beetle infestation are increasing the fire return interval, which increases the likelihood of drought conditions in the growing season (Romme & Turner, 2015). The number of fires has also increased from human influences such as campfires, vehicles, and cigarettes in the last decade (Yellowstone Center for Resources, 2013). Fire stressors from human intervention are more likely to burn during low-moisture summers, which is concerning considering drought conditions in the park are increasing (Yellowstone Center for Resources, 2013). In the early 2000s, Yellowstone experienced several years of drought which resulted in low lake levels and reduced connection between water bodies. As a result, cutthroat trout juveniles were prevented from travelling to their winter habitat in Yellowstone Lake (Koel, et al., 2017). Furthermore, stream temperatures are predicted to increase by 1.4-3.2°F by 2050 (Al-Chokhachy et al. 2013). This increase is predicted to decrease cutthroat populations by 26%, as well as support the reproduction of non-native fish species (Wenger et al. 2011).
In our opinion, Yellowstone National Park’s waterways are a designed ecosystem. The introduction of non-native fish to increase fishing opportunities caused a cascading effect on surrounding terrestrial and aquatic species such as bears, river otters, and birds of prey. As such, the ecosystem was designed for human benefit, rather than to protect or enhance biodiversity. In addition, we argue that the ecosystem is not novel because management efforts are set to reestablish the park’s cutthroat trout population, and therefore restore it to a natural baseline. The introduction of non-native fish may have had more influence on the park than the reintroduction of wolves, as the lack of cutthroat trout caused bears to heavily prey on elk populations and slow the growth of their migratory herds (Goldfarb, 2014). However, cutthroat trout populations are set to be restored with continued management, and this outcome will likely reverse the trophic cascading effects which have occurred (Bigelow, et al., 2017).
References:
Al-Chokhachy, R., J. Alder, S. Hostetler, R. Gresswell, and B. Shepard. (2013). Thermal controls of Yellowstone cutthroat trout and invasive fishes under climate change. Global Change Biology 19(10):3069-3081.
Bigelow, P. E., Doepke, P. D., Ertel, B. D., Guy, C. S., Syslo, J. M., and Koel, T. M. (2017). Suppressing non-native lake trout to restore native cutthroat trout in Yellowstone Lake. Yellowstone Science, 25(1), 53-59.
Bulkley, R. V. (1961). Fluctuations in the age composition and growth rate of cutthroat trout in Yellowstone Lake: U.S. Fish and Wildlife Service. U.S. Government Printing Office, Washington, D.C.
Crait, J. R., and Ben-David, M. (2006). River otters in Yellowstone Lake depend on a declining cutthroat trout population. Journal of Mammalogy 87, 485-494.
Derworiz, C. (2017, July 19). Whirling disease leads to fishing, boating restrictions in Banff National Park. Calgary Herald. Retrieved from https://calgaryherald.com/news/local-news/whirling- disease
Goldfarb, B. (2014, August 19). The Battle to Save Yellowstone from Invasive Fish. Scientific American. Retrieved from https://www.scientificamerican.com/article/the-battle-to-save-yellowstone-from-invasive-fish-slide-show/
Gresswell, R.E., C.S. Guy, M.J. Hansen, M.L. Jones, J.E. Marsden, P.J. Martinez, and J.M. Syslo. ( 2015). Lake trout suppression in Yellowstone Lake: science review panel. Interim scientific assessment, 2014 performance year. A report to the superintendent. YCR-2015-04. National Park Service, Yellowstone National Park, Wyoming, USA.
Iowa Department of Natural Resources. (n.d.) Brook trout [Image]. Retrieved from https://www.iowadnr.gov/Fishing/Iowa-Fish-Species/Fish-Details/SpeciesCode/BKT
Kaeding, L. R. (2012). Are Yellowstone Lake temperatures more suitable to nonnative lake trout than to native cutthroat trout? North American Journal of Fisheries Management, 32, 848-852.
Koel, T. M., Bigelow, P. E., Doepke, P. D., Ertel, B. D., and Mahony, D. L. (2005). Nonnative lake trout result in Yellowstone cutthroat trout decline and impacts to bears and anglers. Fisheries, 30(11), 10-19.
Koel, T. M., Arnold, J.L., Baril, L. A., Gunther, K. A., Smith, D. W., Syslo, J. M., and Tronstad, L. M. (2017). Non-native Lake Trout induce cascading changes in the Yellowstone Lake ecosystem. Yellowstone Science, 25(1), 42-50.
Koel, T.M., Arnold, J.L., Bigelow, P., Detjens, C.R., Doepke, P. D., Ertel,B.D., and Ruhl, M.E. (2015). Native Fish Conservation Program, Yellowstone Fisheries & Aquatic Sciences 2012-2014, Yellowstone National Park. National Park Service, Yellowstone Center for Resources,
Yellowstone National Park, Wyoming, USA, YCR-2015-01.
MacDonald. D. (2018). Before Yellowstone: Native American archaeology in the national park. University of Washington Press, Seattle, Washington, USA.
Manitoba Canada’s Heart Beats. (n.d.) Brown trout [Image]. Retrieved from https://huntfishmanitoba.ca/go-fishing/what-youll-catch/brown-trout
Manitoba Canada’s Heart Beats. (n.d.) Lake trout [Image]. Retrieved from https://huntfishmanitoba.ca/go-fishing/what-youll-catch/lake-trout
Manitoba Canada’s Heart Beats. (n.d.) Rainbow trout [Image]. Retrieved from https://huntfishmanitoba.ca/go-fishing/what-youll-catch/rainbow-trout
Mary Donahue. (n.d.). Yellowstone [Image]. Retrieved from https://marydonahue.org/yellowstone
McIntyre J. D. (1995). Review and assessment of possibilities for protecting the cutthroat trout of Yellowstone Lake from introduced lake trout: proceedings of a workshop and information exchange held in Gardiner, Montana, February 15–17, 1995. Pp. 28–33 in The Yellowstone Lake crisis: confronting a lake trout invasion. A report to the director of the National Park Service (Varley J. D. Schullery P., eds.). Yellowstone Center for Resources, National Park Service, Yellowstone National Park, Wyoming.
Munro, A. R., McMahon, T. E., and Ruzycki, J. R. (2005). Natural chemical markers identify source and date of introduction of an exotic species: lake trout (Salvelinus namaycush) in Yellowstone Lake Canadian Journal of Fisheries and Aquatic Sciences, 62(1), 79-87.
National Park Service. (2018). Fishing. Retrieved from https://www.nps.gov/yell/planyourvisit/fishing.htm
National Park Service. (2019). Fish and aquatic species. Retrieved from https://www.nps.gov/yell/learn/nature/fishaquaticspecies.htm#AIS
National Park Service. (2010). Native Fish Conservation Plan / Environmental Assessment. Edited by Department of the Interior. Yellowstone Center for Resources. Retrieved from https://www.nps.gov/yell/learn/nature/upload/2012-2014_yellowstone_fisheries.pdf
National Park Service. (2017a). New Zealand Mud Snail. Retrieved from https://www.nps.gov/yell/learn/nature/new-zealand-mud-snail.htm
National Park Service. (2017b). Whirling disease. Retrieved from https://www.nps.gov/yell/learn/nature/whirling-disease.htm
ORVIS. (n.d.). Montana Trout Close Up Gallery. Retrieved from http://www.glaciertoyellowstone.com/montana-fly-fishing photos/montana-trout
Pacas, C., and Taylor, M. K. (2015). Nonchemical eradication of an introduced trout from a headwater complex in Banff National Park, Canada. North American Journal of Fisheries Management, 35, 748-754.
Romme, W. H., and Turner, M. G. (2015). Ecological implications of climate change in Yellowstone: Moving into uncharted territory. Yellowstone Science, 23(1), 6-12.
Stamford, M. D., and Taylor, E. B. (2004). Phylogeographical lineages of Arctic grayling (Thymallus arcticus) in North America: divergence, origins and affinities with Eurasian Thymallus. Molecular Ecology, 13, 1533-1549.
Syslo, J.M. 2015. Dynamics of Yellowstone cutthroat trout and lake trout in the Yellowstone Lake ecosystem: a case study for the ecology and management of non-native fishes. Dissertation. Montana State University, Bozeman, Montana, USA.
Stapp P. Hayward G. D. (2002a). Effects of an introduced piscivore on native trout: insights from a demographic model. Biological Invasions, 4, 299-316.
Tomelleri, J. R. (n.d.) Yellowstone cutthroat trout [Image]. Western Native Trout Initiative. Retrieved from http://westernnativetrout.org/yellowstone-cutthroat-trout/
Wenger, S.J., D.J. Isaak, C.H. Luce, H.M. Neville, K.D. Fausch, J.B. Dunham, D.C. Dauwalter, M.K. Young, M.M. Elsner, B.E. Rieman, A.F. Hamlet, and J.E. Williams. (2011). Flow regime, temperature, and biotic interactions drive differential declines of trout species under climate change. Proceedings of the National Academy of Sciences 108(34):14175-14180
Wilkinson, T. (2018). It All Started With a Few Trout. Now Yellowstone’s Iconic Birds Face ‘Collapse.' National Geographic. Retrieved from https://www.nationalgeographic.com/environment/2018/07/ yellowstone-lake-trout-trumpeter-swan-avian-collapse-animals/
Yellowstone. (2017). Official Yellowstone National Park Map [PDF]. Retrieved from https://www.yellowstonepark.com/park/official-yellowstone-national-park-map-pdf
Yellowstone Center for Resources. 2013. Yellowstone National Park: Natural and Cultural Resources Vital Signs. National Park Service, Mammoth Hot Springs, Wyoming, YCR-2013-03. Retrieved from https://www.nps.gov/yell/learn/management/upload/vitalsigns2-2.pdf
Yellowstone Forever. (n.d.). Save the Yellowstone cutthroat trout. Retrieved from https://www.yellowstone.org/what-we-do/native-fish/
Bigelow, P. E., Doepke, P. D., Ertel, B. D., Guy, C. S., Syslo, J. M., and Koel, T. M. (2017). Suppressing non-native lake trout to restore native cutthroat trout in Yellowstone Lake. Yellowstone Science, 25(1), 53-59.
Bulkley, R. V. (1961). Fluctuations in the age composition and growth rate of cutthroat trout in Yellowstone Lake: U.S. Fish and Wildlife Service. U.S. Government Printing Office, Washington, D.C.
Crait, J. R., and Ben-David, M. (2006). River otters in Yellowstone Lake depend on a declining cutthroat trout population. Journal of Mammalogy 87, 485-494.
Derworiz, C. (2017, July 19). Whirling disease leads to fishing, boating restrictions in Banff National Park. Calgary Herald. Retrieved from https://calgaryherald.com/news/local-news/whirling- disease
Goldfarb, B. (2014, August 19). The Battle to Save Yellowstone from Invasive Fish. Scientific American. Retrieved from https://www.scientificamerican.com/article/the-battle-to-save-yellowstone-from-invasive-fish-slide-show/
Gresswell, R.E., C.S. Guy, M.J. Hansen, M.L. Jones, J.E. Marsden, P.J. Martinez, and J.M. Syslo. ( 2015). Lake trout suppression in Yellowstone Lake: science review panel. Interim scientific assessment, 2014 performance year. A report to the superintendent. YCR-2015-04. National Park Service, Yellowstone National Park, Wyoming, USA.
Iowa Department of Natural Resources. (n.d.) Brook trout [Image]. Retrieved from https://www.iowadnr.gov/Fishing/Iowa-Fish-Species/Fish-Details/SpeciesCode/BKT
Kaeding, L. R. (2012). Are Yellowstone Lake temperatures more suitable to nonnative lake trout than to native cutthroat trout? North American Journal of Fisheries Management, 32, 848-852.
Koel, T. M., Bigelow, P. E., Doepke, P. D., Ertel, B. D., and Mahony, D. L. (2005). Nonnative lake trout result in Yellowstone cutthroat trout decline and impacts to bears and anglers. Fisheries, 30(11), 10-19.
Koel, T. M., Arnold, J.L., Baril, L. A., Gunther, K. A., Smith, D. W., Syslo, J. M., and Tronstad, L. M. (2017). Non-native Lake Trout induce cascading changes in the Yellowstone Lake ecosystem. Yellowstone Science, 25(1), 42-50.
Koel, T.M., Arnold, J.L., Bigelow, P., Detjens, C.R., Doepke, P. D., Ertel,B.D., and Ruhl, M.E. (2015). Native Fish Conservation Program, Yellowstone Fisheries & Aquatic Sciences 2012-2014, Yellowstone National Park. National Park Service, Yellowstone Center for Resources,
Yellowstone National Park, Wyoming, USA, YCR-2015-01.
MacDonald. D. (2018). Before Yellowstone: Native American archaeology in the national park. University of Washington Press, Seattle, Washington, USA.
Manitoba Canada’s Heart Beats. (n.d.) Brown trout [Image]. Retrieved from https://huntfishmanitoba.ca/go-fishing/what-youll-catch/brown-trout
Manitoba Canada’s Heart Beats. (n.d.) Lake trout [Image]. Retrieved from https://huntfishmanitoba.ca/go-fishing/what-youll-catch/lake-trout
Manitoba Canada’s Heart Beats. (n.d.) Rainbow trout [Image]. Retrieved from https://huntfishmanitoba.ca/go-fishing/what-youll-catch/rainbow-trout
Mary Donahue. (n.d.). Yellowstone [Image]. Retrieved from https://marydonahue.org/yellowstone
McIntyre J. D. (1995). Review and assessment of possibilities for protecting the cutthroat trout of Yellowstone Lake from introduced lake trout: proceedings of a workshop and information exchange held in Gardiner, Montana, February 15–17, 1995. Pp. 28–33 in The Yellowstone Lake crisis: confronting a lake trout invasion. A report to the director of the National Park Service (Varley J. D. Schullery P., eds.). Yellowstone Center for Resources, National Park Service, Yellowstone National Park, Wyoming.
Munro, A. R., McMahon, T. E., and Ruzycki, J. R. (2005). Natural chemical markers identify source and date of introduction of an exotic species: lake trout (Salvelinus namaycush) in Yellowstone Lake Canadian Journal of Fisheries and Aquatic Sciences, 62(1), 79-87.
National Park Service. (2018). Fishing. Retrieved from https://www.nps.gov/yell/planyourvisit/fishing.htm
National Park Service. (2019). Fish and aquatic species. Retrieved from https://www.nps.gov/yell/learn/nature/fishaquaticspecies.htm#AIS
National Park Service. (2010). Native Fish Conservation Plan / Environmental Assessment. Edited by Department of the Interior. Yellowstone Center for Resources. Retrieved from https://www.nps.gov/yell/learn/nature/upload/2012-2014_yellowstone_fisheries.pdf
National Park Service. (2017a). New Zealand Mud Snail. Retrieved from https://www.nps.gov/yell/learn/nature/new-zealand-mud-snail.htm
National Park Service. (2017b). Whirling disease. Retrieved from https://www.nps.gov/yell/learn/nature/whirling-disease.htm
ORVIS. (n.d.). Montana Trout Close Up Gallery. Retrieved from http://www.glaciertoyellowstone.com/montana-fly-fishing photos/montana-trout
Pacas, C., and Taylor, M. K. (2015). Nonchemical eradication of an introduced trout from a headwater complex in Banff National Park, Canada. North American Journal of Fisheries Management, 35, 748-754.
Romme, W. H., and Turner, M. G. (2015). Ecological implications of climate change in Yellowstone: Moving into uncharted territory. Yellowstone Science, 23(1), 6-12.
Stamford, M. D., and Taylor, E. B. (2004). Phylogeographical lineages of Arctic grayling (Thymallus arcticus) in North America: divergence, origins and affinities with Eurasian Thymallus. Molecular Ecology, 13, 1533-1549.
Syslo, J.M. 2015. Dynamics of Yellowstone cutthroat trout and lake trout in the Yellowstone Lake ecosystem: a case study for the ecology and management of non-native fishes. Dissertation. Montana State University, Bozeman, Montana, USA.
Stapp P. Hayward G. D. (2002a). Effects of an introduced piscivore on native trout: insights from a demographic model. Biological Invasions, 4, 299-316.
Tomelleri, J. R. (n.d.) Yellowstone cutthroat trout [Image]. Western Native Trout Initiative. Retrieved from http://westernnativetrout.org/yellowstone-cutthroat-trout/
Wenger, S.J., D.J. Isaak, C.H. Luce, H.M. Neville, K.D. Fausch, J.B. Dunham, D.C. Dauwalter, M.K. Young, M.M. Elsner, B.E. Rieman, A.F. Hamlet, and J.E. Williams. (2011). Flow regime, temperature, and biotic interactions drive differential declines of trout species under climate change. Proceedings of the National Academy of Sciences 108(34):14175-14180
Wilkinson, T. (2018). It All Started With a Few Trout. Now Yellowstone’s Iconic Birds Face ‘Collapse.' National Geographic. Retrieved from https://www.nationalgeographic.com/environment/2018/07/ yellowstone-lake-trout-trumpeter-swan-avian-collapse-animals/
Yellowstone. (2017). Official Yellowstone National Park Map [PDF]. Retrieved from https://www.yellowstonepark.com/park/official-yellowstone-national-park-map-pdf
Yellowstone Center for Resources. 2013. Yellowstone National Park: Natural and Cultural Resources Vital Signs. National Park Service, Mammoth Hot Springs, Wyoming, YCR-2013-03. Retrieved from https://www.nps.gov/yell/learn/management/upload/vitalsigns2-2.pdf
Yellowstone Forever. (n.d.). Save the Yellowstone cutthroat trout. Retrieved from https://www.yellowstone.org/what-we-do/native-fish/