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Glassic HC, Guy CS, Tronstad LM, Lujan DR, Briggs MA, Albertson LK, Koel TM. Invasive predator diet plasticity has implications for native fish conservation and invasive species suppression. PLoS One 2023; 18:e0279099. [PMID: 36827303 PMCID: PMC9956068 DOI: 10.1371/journal.pone.0279099] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Accepted: 11/29/2022] [Indexed: 02/25/2023] Open
Abstract
Diet plasticity is a common behavior exhibited by piscivores to sustain predator biomass when preferred prey biomass is reduced. Invasive piscivore diet plasticity could complicate suppression success; thus, understanding invasive predator consumption is insightful to meeting conservation targets. Here, we determine if diet plasticity exists in an invasive apex piscivore and whether plasticity could influence native species recovery benchmarks and invasive species suppression goals. We compared diet and stable isotope signatures of invasive lake trout and native Yellowstone cutthroat trout (cutthroat trout) from Yellowstone Lake, Wyoming, U.S.A. as a function of no, low-, moderate-, and high-lake trout density states. Lake trout exhibited plasticity in relation to their density; consumption of cutthroat trout decreased 5-fold (diet proportion from 0.89 to 0.18) from low- to high-density state. During the high-density state, lake trout switched to amphipods, which were also consumed by cutthroat trout, resulting in high diet overlap (Schoener's index value, D = 0.68) between the species. As suppression reduced lake trout densities (moderate-density state), more cutthroat trout were consumed (proportion of cutthroat trout = 0.42), and diet overlap was released between the species (D = 0.30). A shift in lake trout δ13C signatures from the high- to the moderate-density state also corroborated increased consumption of cutthroat trout and lake trout diet plasticity. Observed declines in lake trout are not commensurate with expected cutthroat trout recovery due to lake trout diet plasticity. The abundance of the native species in need of conservation may take longer to recover due to the diet plasticity of the invasive species. The changes observed in diet, diet overlap, and isotopes associated with predator suppression provides more insight into conservation and suppression dynamics than using predator and prey biomass alone. By understanding these dynamics, we can better prepare conservation programs for potential feedbacks caused by invasive species suppression.
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Affiliation(s)
- Hayley C. Glassic
- Montana Cooperative Fishery Research Unit, Department of Ecology, Montana State University, Bozeman, Montana, United States of America,* E-mail:
| | - Christopher S. Guy
- Department of Ecology, U.S. Geological Survey, Montana Cooperative Fishery Research Unit, Montana State University, Bozeman, Montana, United States of America
| | - Lusha M. Tronstad
- Wyoming Natural Diversity Database, University of Wyoming, Laramie, Wyoming, United States of America
| | - Dominique R. Lujan
- Department of Zoology and Physiology, University of Wyoming, Laramie, Wyoming, United States of America
| | - Michelle A. Briggs
- Montana Cooperative Fishery Research Unit, Department of Ecology, Montana State University, Bozeman, Montana, United States of America,Department of Ecology, Montana State University, Bozeman, Montana, United States of America
| | - Lindsey K. Albertson
- Department of Ecology, Montana State University, Bozeman, Montana, United States of America
| | - Todd M. Koel
- U.S. National Park Service, Yellowstone Center for Resources, Native Fish Conservation Program, Yellowstone National Park, Wyoming, United States of America
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Of olives and carp: interactive effects of an aquatic and a terrestrial invader on a stream‐riparian ecosystem. Ecosphere 2021. [DOI: 10.1002/ecs2.3789] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Abstract
Invasive predatory lake trout Salvelinus namaycush were discovered in Yellowstone Lake in 1994 and caused a precipitous decrease in abundance of native Yellowstone cutthroat trout Oncorhynchus clarkii bouvieri. Suppression efforts (primarily gillnetting) initiated in 1995 did not curtail lake trout population growth or lakewide expansion. An adaptive management strategy was developed in 2010 that specified desired conditions indicative of ecosystem recovery. Population modeling was used to estimate effects of suppression efforts on the lake trout and establish effort benchmarks to achieve negative population growth (λ < 1). Partnerships enhanced funding support, and a scientific review panel provided guidance to increase suppression gillnetting effort to >46,800 100-m net nights; this effort level was achieved in 2012 and led to a reduction in lake trout biomass. Total lake trout biomass declined from 432,017 kg in 2012 to 196,675 kg in 2019, primarily because of a 79% reduction in adults. Total abundance declined from 925,208 in 2012 to 673,983 in 2019 but was highly variable because of recruitment of age-2 fish. Overall, 3.35 million lake trout were killed by suppression efforts from 1995 to 2019. Cutthroat trout abundance remained below target levels, but relative condition increased, large individuals (> 400 mm) became more abundant, and individual weights doubled, probably because of reduced density. Continued actions to suppress lake trout will facilitate further recovery of the cutthroat trout population and integrity of the Yellowstone Lake ecosystem.
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Koel TM, Tronstad LM, Arnold JL, Gunther KA, Smith DW, Syslo JM, White PJ. Predatory fish invasion induces within and across ecosystem effects in Yellowstone National Park. SCIENCE ADVANCES 2019; 5:eaav1139. [PMID: 30906863 PMCID: PMC6426464 DOI: 10.1126/sciadv.aav1139] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Accepted: 01/31/2019] [Indexed: 05/30/2023]
Abstract
Predatory fish introduction can cause cascading changes within recipient freshwater ecosystems. Linkages to avian and terrestrial food webs may occur, but effects are thought to attenuate across ecosystem boundaries. Using data spanning more than four decades (1972-2017), we demonstrate that lake trout invasion of Yellowstone Lake added a novel, piscivorous trophic level resulting in a precipitous decline of prey fish, including Yellowstone cutthroat trout. Plankton assemblages within the lake were altered, and nutrient transport to tributary streams was reduced. Effects across the aquatic-terrestrial ecosystem boundary remained strong (log response ratio ≤ 1.07) as grizzly bears and black bears necessarily sought alternative foods. Nest density and success of ospreys greatly declined. Bald eagles shifted their diet to compensate for the cutthroat trout loss. These interactions across multiple trophic levels both within and outside of the invaded lake highlight the potential substantial influence of an introduced predatory fish on otherwise pristine ecosystems.
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Affiliation(s)
- Todd M. Koel
- Yellowstone Center for Resources, Mammoth Hot Springs, Yellowstone National Park, WY 82190, USA
| | - Lusha M. Tronstad
- Wyoming Natural Diversity Database, University of Wyoming, Laramie, WY 82071, USA
| | - Jeffrey L. Arnold
- Yellowstone Center for Resources, Mammoth Hot Springs, Yellowstone National Park, WY 82190, USA
| | - Kerry A. Gunther
- Yellowstone Center for Resources, Mammoth Hot Springs, Yellowstone National Park, WY 82190, USA
| | - Douglas W. Smith
- Yellowstone Center for Resources, Mammoth Hot Springs, Yellowstone National Park, WY 82190, USA
| | - John M. Syslo
- Montana Cooperative Fishery Research Unit, Montana State University, Bozeman, MT 59717, USA
| | - Patrick J. White
- Yellowstone Center for Resources, Mammoth Hot Springs, Yellowstone National Park, WY 82190, USA
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Hall SJ, Huber DP, Hughes RF. Invasion of Hawaiian rainforests by an introduced amphibian predator and N2-fixing tree increases soil N2O emissions. Ecosphere 2018. [DOI: 10.1002/ecs2.2416] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Affiliation(s)
- Sharon J. Hall
- School of Life Sciences; Arizona State University; Tempe Arizona 85287-4501 USA
| | - David P. Huber
- Northwest Watershed Research Center; USDA-Agricultural Research Service; Boise Idaho 83712 USA
| | - R. Flint Hughes
- Institute for Pacific Islands Forestry; Pacific Southwest Research Station; USDA Forest Service; Hilo Hawaii 96720 USA
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