Myxobolus cerebralis (Hofer) infection risk in native cutthroat trout Oncorhynchus clarkii (Richardson) and its relationships to tributary environments in the Yellowstone Lake Basin

2014 ◽  
Vol 38 (7) ◽  
pp. 637-652 ◽  
Author(s):  
S Murcia ◽  
B L Kerans ◽  
T M Koel ◽  
E MacConnell

<em>Abstract</em>.—Lahontan Cutthroat Trout (LCT) <em>Oncorhynchus clarkii henshawi </em>and Paiute Cutthroat Trout (PCT) <em>O. c. selernis </em>are found in the Lahontan hydrographic basin of northern Nevada, northeastern California, and southeastern Oregon and together form the Lahontan Basin evolutionary lineage of Cutthroat Trout <em>O. clarkii</em>. The Alvord Cutthroat Trout <em>O. c. </em>ssp. native to the Alvord Lake subbasin in the northwestern Lahontan Basin was also part of this lineage but went extinct due to Rainbow Trout <em>O. mykiss </em>introgression in the mid-20th century. Both LCT and PCT are federally listed as threatened under the U.S. Endangered Species Act. Given its historic distribution in a single small stream and both phenotypic and genetic distinctiveness, PCT is currently recognized as a separate evolutionarily significant unit (ESU). For LCT, three ESUs are identified based upon meristic, morphological, ecological, and genetic data. These putative LCT ESUs separate lacustrine forms in the western Lahontan Basin (Truckee, Carson, and Walker River basins) from largely fluvial forms in the eastern Lahontan Basin (Humboldt and Reese River basins) and northwestern Lahontan Basin (Quinn River, Coyote Lake, and Summit Lake basins). The more recent recognition of a much longer evolutionary history of Cutthroat Trout and several influential genetic papers identifying previously unrecognized diversity within Cutthroat Trout have prompted a need to re-evaluate the overall taxonomy of this species. Here, we review earlier literature and draw on new information from recent studies to delineate uniquely identifiable evolutionary units within the Lahontan Basin lineage of Cutthroat Trout. Though in several cases various anthropogenic and natural influences have made definitive conclusions difficult, based on this collective information and the goal of conserving potentially important genetic, evolutionary, and life history diversity, we propose recognition of six uniquely identifiable evolutionary units within the Lahontan Cutthroat Trout lineage: (1) Paiute Cutthroat Trout—upper East Carson River; (2) western Lahontan Basin—Truckee, Walker, and Carson rivers together with Summit Lake; (3) northwestern Lahontan Basin—Quinn River; (4) eastern Lahontan Basin—Humboldt and Reese rivers; (5) Lake Alvord basin—Virgin-Thousand and Trout Creek drainages; and (6) Coyote Lake basin—Willow and Whitehorse rivers.



2019 ◽  
Vol 76 (3) ◽  
pp. 426-437 ◽  
Author(s):  
Teresa Campbell ◽  
James Simmons ◽  
Jessica Sáenz ◽  
Christopher L. Jerde ◽  
William Cowan ◽  
...  

Population connectivity between resident and migratory cutthroat trout (Oncorhynchus clarkii ssp.) is understudied, but has implications for population viability and management. We examined evidence for stream residency, studied the spatial patterns of stream use by adfluvial and stream-resident trout, and measured migration rates with changing stream depth for Lahontan cutthroat trout (Oncorhynchus clarkii henshawi) in the Summit Lake Basin, Nevada (USA). Passive integrated transponder technology and a fry trap were used to track fish movements and identify the distribution of resident and adfluvial trout. Stream residents were distributed throughout the network. Adfluvial spawners concentrated in lower reaches, but also migrated up to 12.9 km. Adfluvial juveniles migrated to the lake from lower reaches and from upstream of adfluvial spawners. High stream depths coincided with more adfluvial juveniles migrating to the lake and more adfluvial spawners moving into the stream, which led to more accessing the upper watershed. This work shows that connectivity is central to adfluvial–resident Lahontan cutthrout trout population dynamics and may lead to increased probability of persistence — a characteristic of these isolated, threatened trout populations.



Fishes ◽  
2020 ◽  
Vol 5 (2) ◽  
pp. 18 ◽  
Author(s):  
Todd M. Koel ◽  
Jeffery L. Arnold ◽  
Patricia E. Bigelow ◽  
Travis O. Brenden ◽  
Jeffery D. Davis ◽  
...  

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.



Author(s):  
Camille J. Macnaughton ◽  
Travis C. Durhack ◽  
Neil J. Mochnacz ◽  
Eva C. Enders

The physiology and behaviour of fish are strongly affected by ambient water temperature. Physiological traits related to metabolism, such as aerobic scope (AS), can be measured across temperature gradients and the resulting performance curve reflects the thermal niche that fish can occupy. We measured AS of Westslope Cutthroat Trout (Oncorhynchus clarkii lewisi) at 5, 10, 15, 20, and 22°C and compared temperature preference (Tpref) of the species to non-native Brook Trout, Brown Trout, and Rainbow Trout. Intermittent-flow respirometry experiments demonstrated that metabolic performance of Westslope Cutthroat Trout was optimal at ~15 °C and decreased substantially beyond this temperature, until lethal temperatures at ~25 °C. Adjusted preferred temperatures across species (Tpref) were comparatively high, ranging from 17.8-19.9 °C, with the highest Tpref observed for Westslope Cutthroat Trout. Results suggest that although Westslope Cutthroat Trout is considered a cold-water species, they do not prefer or perform as well in cold water (≤ 10°C), thus, can occupy a warmer thermal niche than previously thought. The metabolic performance curve (AS) can be used to develop species‐specific thermal criteria to delineate important thermal habitats and guide conservation and recovery actions for Westslope Cutthroat Trout.





2018 ◽  
Vol 30 (4) ◽  
pp. 264-279 ◽  
Author(s):  
R. Barry Nehring ◽  
John Alves ◽  
Joshua B. Nehring ◽  
Benjamin Felt


Author(s):  
Jamie Crait ◽  
Merav Ben-David ◽  
Bob Hall

Yellowstone National Park (YNP) is a treasured national resource and an important element of tourism and the recreational economy in Wyoming. Because of its unique geological features and abundant wildlife and fisheries, YNP is a tourist destination for millions of people annually. Although this national symbol is cherished for its pristine condition and has been protected from most human influence for over 100 years, human mediated invasions of non­ indigenous species, such as several species of plants and animals, including an exotic snail (Potamopyrgus antipodarum), may alter this ecosystem. Recently an unauthorized introduction of lake trout (Salvelinus namaycush) to Yellowstone Lake was documented. Recent investigation at the University of Wyoming, indicated that in-lake predation by lake trout on juvenile and sub-adult native Yellowstone cutthroat trout (Oncorhyncus clarki bouvieri) could negatively influence recruitment of cutthroat trout (Stapp and Hayward 2002). This may lead to significant reductions in numbers of spawning adult cutthroat if current management actions are ineffective, or if they are not continuously pursued (Stapp and Hayward 2002). While lake trout invasion in Yellowstone Lake will likely have detrimental effects on in-lake communities and processes, reductions in populations of native cutthroat trout can potentially impact other aquatic and terrestrial ecosystems outside of Yellowstone Lake. Cutthroat trout in Yellowstone Lake annually migrate into tributary streams and rivers to spawn (Varley and Gresswell 1988), with runs up to 60,000 trout per season into small streams such as Clear Creek (Gresswell and Varley 1988). This spawning migration may significantly affect in­ stream communities (cf. Power 1990) and alter nutrient cycling within tributary streams (Peterson et al. 1993) and in the adjacent riparian forests (Ben­David et al. 1998; Hilderbrand et al. 1999). Therefore, spawning cutthroat trout not only have trophic effects on their ecosystem but also act as "ecosystem engineers" (i.e., species that influence structure and function of ecosystems through non­ trophic processes) because of their role in transporting large amounts of nutrients between ecosystems (Jones et al. 1994). Reductions in spawning adult cutthroat trout will likely alter in­stream processes. In addition, for piscivorous (fish­eating) predators, a significant decline in the number of adult spawning cutthroat trout may reduce recruitment and survival, and it could threaten viability of predator populations. In this project we are investigating the role of cutthroat trout in structuring stream ecosystems, their importance to a representative fish-predator - the river otter (Lontra canadensis), and possible effectson terrestrial plants through nutrient transport by otters to latrine sites (Ben-David et al. 1998 Hilderbrand et al. 1999). We hypothesize that the spawning migration of cutthroat trout will result in transport of nutrients from lake to streams, and from streams to terrestrial forests, through the activity of piscivorous predators. Because nitrogen (N) limits production in area streams (J. L. Tank and R 0. Hall unpublished data) and terrestrial ecosystems (Nadelhoffer et al. 1995) we focus our investigation of nutrient cycling on this element. These observations will enable us to predict how streams, trout predators, and the terrestrial landscape will be affected following cutthroat trout decline.



Author(s):  
Ryan Kovach ◽  
Lisa Eby

The cutthroat trout Oncorhynchus clarki is Wyoming's only native trout. The Yellowstone cutthroat trout (Oncorhynchus clarkii bouvieri) is designated as a "species of special concern" by a number of agencies and conservation groups. Although the Yellowstone cutthroat trout has recently avoided federal listing because of robust headwater populations (USFWS 2006), they face continued threats across their range. The fine-spotted Snake River native trout is a morphologically divergent ecotype of the Yellowstone subspecies, although it is not genetically distinguishable (Allendorf and Leary 1988, Novak et al. 2005). The Gros Ventre, an important tributary of the Snake River located partially in Grand Teton National Park, historically supported robust populations of fine­ spotted Snake River cutthroat trout. Principal threats to Gros Ventre native trout, especially in the lower end of the drainage within the park boundaries, include both water diversions (loss of water and fish into irrigation ditches) and presence of exotic species.



Author(s):  
Ernest R Keeley ◽  
Janet L Loxterman ◽  
Sammy L Matsaw ◽  
Zacharia M Njoroge ◽  
Meredith B Seiler ◽  
...  

The cutthroat trout, Oncorhynchus clarkii (Richardson, 1836), is one of the most widely distributed species of freshwater fish in western North America. Occupying a diverse range of habitats, they exhibit significant phenotypic variability that is often recognized by intraspecific taxonomy. Recent molecular phylogenies have described phylogenetic diversification across cutthroat trout populations, but no study has provided a range-wide morphological comparison of taxonomic divisions. In this study, we used linear and geometric-based morphometrics to determine if phylogenetic and subspecies divisions correspond to morphological variation in cutthroat trout, using replicate populations from throughout the geographic range of the species. Our data indicate significant morphological divergence of intraspecific categories in some, but not all, cutthroat trout subspecies. We also compare morphological distance measures with distance measures of mtDNA sequence divergence. DNA sequence divergence was positively correlated with morphological distance measures, indicating that morphologically more similar subspecies have lower sequence divergence in comparison to morphologically distant subspecies. Given these results, integrating both approaches to describing intraspecific variation may be necessary for developing a comprehensive conservation plan in wide-ranging species.



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