Lahontan Cutthroat Trout: Advances and Developments in Conservation, Science, and Management (hosted by AFS)

Symposium
ROOM: Atlantis, Grand Ballroom 2
SESSION NUMBER: 8053
 
Lahontan Cutthroat Trout (LCT) are one of the iconic animals of the Great Basin and largest of the subspecies of Cutthroat Trout. LCT from terminal lakes were commonly found in the 20 to 30-pound range. LCT have not fared well in the past 100-plus years, being displaced from more than 95% of their historic range and have been listed as Threatened under the Endangered Species Act since the 1970s. Recently LCT conservation partners have been engaged in updating goals, objectives and the approach to restoration efforts for LCT using current conservation science framework. This symposium will highlight recent contributions from research, science, management, and conservation for LCT.

8:00AM Piecing Together the Evolutionary History of Lahontan and Paiute Cutthroat Trout: What Do Meristic, Morphological, Ecological, Genetic, and Geological Data Tell Us?
  Mary M. Peacock, Helen Neville, Amanda Finger
Lahontan (Oncorhynchus clarkii henshawi) and Paiute (O. c. selernis) Cutthroat Trout 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. Both LCT and PCT are federally listed as threatened under the United States Endangered Species Act. Given its small distribution in one historic stream and its phenotype and genetic distinctiveness, PCT is recognized currently as a single evolutionarily significant unit (ESU) with no recognized genetic subdivision. Three ESUs have identified for LCT based upon meristic, morphological, ecological, and genetic data. These putative ESUs separate lacustrine forms in the Western Lahontan Basin (Truckee, Carson, and Walker river basins) from largely fluvial forms in the Eastern (Humboldt and Reese river basins) and Northwestern (Quinn River, Coyote Lake, and Summit Lake basins) Lahontan basins. The more recent recognition of a much longer evolutionary history and identification of 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.
8:20AM Genetic Monitoring of a Threatened Trout and Congruency with Extinction Risk Estimated Using Multiple Population Viability Analysis
  Helen Neville, Michael Miller, Mary M. Peacock, Daniel Dauwalter, Doug Leasure, Seth Wenger
Genetic monitoring can provide insight about the status of populations with an efficiency not easily matched by demographic sampling, and thus is particularly appealing for a widely-dispersed species like the threatened Lahontan cutthroat trout (Oncorhynchus clarkii henshawi, LCT). We sequenced samples from 50 LCT conservation populations across the species range plus temporal samples from 19 of these populations spanning 5-20 years. Inclusion of sequences from rainbow trout, a hybridization threat to LCT, uncovered significant hybridization in one key recovery population and hybrid individuals in several others. Evaluation of two estimates of theta (4Nµ, Watterson’s θW and Tajima’s θT), and their difference as an indication of genetic trajectory, highlighted many populations with relatively low genetic diversity and negative genetic trajectories. Populations with temporal samples showed either reduced genetic diversity, worsening genetic trajectory, or both. The only exception was for 3 stream tributaries that were previously reconnected to their mainstem corridor after passage barriers were removed; all three reconnected tributaries showed increasing genetic diversity and improving genetic trajectories, illustrating the genetic benefit of reconnection as a management action. Finally, we used estimates of extinction risk from a Multiple Population Viability Analysis for LCT to further verify information from genetic monitoring for LCT.
8:40AM Evaluation of Monitoring Scenarios to Inform Multiple Population Viability Analysis for Lahontan Cutthroat Trout
  Doug Leasure, Daniel Dauwalter, Seth Wenger, Helen Neville
Strategic conservation often requires understanding the status of all populations across a species range. Historically, trout population status has been inferred by extent of habitat occupied, population size at one point in time, or trends in abundance at sites. Population viability analysis integrates information on population size, growth rate, and stochasticity to estimate probability of extinction for a population. Multiple Population Viability Analysis (MPVA) integrates habitat condition and demographic data in a Bayesian hierarchical modelling framework to estimate extinction probability for all populations across a species’ range, including those sparsely sampled. We evaluated how different monitoring scenarios influenced the performance of a MPVA developed for Lahontan Cutthroat Trout. Scenarios included 1-pass versus 3-pass electrofishing, a variable number of sample sites per population, and rotating panel and staggered sampling designs. Preliminary results suggest that employing multiple-pass electrofishing is important in reducing the frequency of false extinctions, and that sampling more sites on a population improves estimates MPVA performance. Results will be used to inform future agency monitoring for Lahontan Cutthroat Trout, and new monitoring data will be used in future updates of MPVA so conservation efforts can continually be focused on populations most at risk to extinction.
9:00AM Population Dynamics of Threatened Lahontan Cutthroat Trout from the Last Two Remnant Lakes with Natural Recruitment
  James Simmons, Teresa Campbell, Christopher Jerde, Sudeep Chandra, William Cowan, Zeb Hogan, Jessica Saenz
Native self-sustaining populations of adfluvial LCT now occur in just two lakes: desert terminal Summit Lake and montane Independence Lake. We compared their population growth rates, and performed sensitivity analyses to identify the most important vital rates for each population. We applied a stage-classified (Lefkovitch) matrix population model (with skipped spawning) to each population, and parameterized the models with data and parameters from studies of the populations. The Independence and Summit Lake population growth rates both indicated decline (0.94 and .52<1, respectively), and they shared the third most sensitive parameter, low repeat spawning rates (0.44 and 0.36, respectively). However, fry (0.03) and juvenile survival (0.25) had the most impact at Independence Lake; whereas, low transition rates from nonspawning to spawning or nonspawning (0.11 and 0.53, respectively) had the most impact at Summit Lake. Also, the large difference between Independence Lake and Summit Lake fecundity (87 and 0.85, respectively) likely had large effects on their growth rates. The finding suggests that managers focus efforts on protecting juvenile life stages in Independence Lake and adult stages in Summit Lake, and to not assume that intra-specific populations have the same population drivers, especially populations in disparate habitats.
9:20AM A Multi-Faceted Approach to Understanding the Relationship between Lahontan Cutthroat Trout and Their Prey in Pyramid Lake to Guide a New Adaptive Management Program.
  Phaedra Budy, Gary P. Thiede
In aquatic systems exposed to heavy stocking and intense harvest, predator and prey can be decoupled, challenging management and conservation efforts. Lahontan cutthroat trout (LCT) Oncorhynchus clarkii henshawi are highly imperiled throughout their native range, yet currently are thriving in Pyramid Lake, NV. Effective management of this important sport fish relies on understanding their carrying capacity and management actions (stocking, harvest). We combined a large field sampling campaign, bioenergetics modeling, and a cohort analysis to explore the relationship between LCT and their primary prey source, tui chub Gila bicolor. We estimated LCT consumed between 60-76% of tui chub production annually, determined LCT are currently not limited by food, and have not exceeded their carrying capacity. However, although tui chub abundance has been highly variable over time, the catch per unit effort (CPUE) of tui chub has demonstrated a significant decreasing trend since the mid-1980s. Factors that explained a significant amount of variation in tui chub CPUE included total phosphorus (TP), water temperature (for both shallow and deep depths), lake elevation, and zooplankton density. We used this collective body of data to develop an adaptive management plan, meant to be tested with annual monitoring data.
09:40AM Break
1:10PM The Life-Histories and Factors Limiting Lahontan Cutthroat Trout in the Lower Truckee River: New Information from the First Wild Reproduction Events in over 80 Years
  Robert Al-Chokhachy, Roger Peka, Erik Horgen, David Miller, Tim Loux, Lisa Heki
Historically, Lahontan Cutthroat Trout were an important cultural resource for the Pyramid Lake-Paiute Tribe and a valuable fishery. However, due to numerous factors, the LCT population in Pyramid lake and the lower Truckee River was extirpated in the 1940s and maintained through hatchery stocking. A major step towards recovery occurred in 2014, when for the first time in 80 years adfluvial Lahontan Cutthroat Trout spawned in the Truckee River (2014-present). Here, we describe the early results of ongoing studies to quantify LCT spawning migrations, outmigration of young-of-year (YOY) to Pyramid Lake, and factors constraining success. Dates of adult migration varied across years, driven by differences in discharge (range = 772 – 10,200 cfs) and temperature (range = 15 – 23.6oC). The timing and size of YOY emigration was linked to hydrologic and thermal conditions, as individual migrations typically ceased at temperatures >25°C, nearing the lethal limit for LCT. The rate of stream warming and timing of adult migration also had considerable effects on size at emigration. Using hydroacoustic tracking of adults, we illustrate the importance of removing additional barriers to migration. We further discuss these results in the context of water management and recovery of LCT in the Truckee River.
1:30PM Lahontan Cutthroat Trout Spawning Runs at the Marble Bluff Fish Passage and Research Facility, Nixon, NV
  Roger Peka, Robert Al-Chokhachy, Lisa Heki, Tim Loux, Erik Horgen, David Miller
Lahontan cutthroat trout (Oncorhynchus clarkii henshawi, LCT) is a threatened species native to Eastern California and Northern Nevada, and the only native trout in the Lake Tahoe-Pyramid Lake watershed. LCT were extirpated from Pyramid Lake by 1943. In the 1970s, a stocking program that used LCT from outside sources recreated a sport fishery in Pyramid Lake. The discovery of a remnant LCT population (Pilot Peak) and genetic confirmation of their Pyramid Lake origin led to the establishment of a conservation broodstock. Pilot Peak LCT have been stocked in Pyramid Lake since 2006, and successful wild reproduction in the lower Truckee River has been document every year since 2014. Here, we consider the life history of native lacustrine LCT in this new context. Pilot Peak LCT angler catch rates, size, and spawning runs at Marble Bluff have increased remarkably. Run timing correlates with river flow and temperature. Tagging data indicates many of these LCT are delaying their spawning runs until age 7 or older. Preliminary data for 2018 suggests this will be the largest Pilot Peak spawning run in both numbers and average size. While challenges remain, the Pilot Peak LCT program has been a model for a conservation genetics approach.
1:50PM Quantifying Pelagic Food Web Interactions in Lake Tahoe: A Roadmap for the Reintroduction of Lahontan Cutthroat Trout
  Adam Hansen, David Beauchamp
Previous studies evaluating potential limiting factors for reintroduced Lahontan cutthroat trout emphasized the need to elucidate food web interactions, yet important knowledge gaps regarding trophic interactions among pelagic fishes and invertebrates in Lake Tahoe remain. We quantified the abundance and consumption demand of planktivores with an emphasis on kokanee and Mysis diluviana. We synthesized this new information with existing information for lake trout. The seasonal supply of adult copepods satisfied the consumption demand of kokanee, but only supported low feeding and growth rates. Kokanee relied heavily on Mysis as supplemental prey, an unusual and unexpected result. Mysis were omnivorous, but copepods contributed little to their diet, and a high degree of herbivory was apparent. However, the consumption demand of Mysis on copepods still exceeded that of kokanee. Lake trout relied heavily on Mysis. Predation on kokanee appeared to only involve lake trout >625 mm, and was presumably focused on pre-spawning aggregations. Consumption of Mysis by lake trout and kokanee together represented a significant source of mortality when compared to the production of Mysis. Despite the presence of Mysis and a Mysis-fueled lake trout population, kokanee have persisted; an intriguing pattern when considering potential ecological bottlenecks for reintroduced Lahontan cutthroat trout.
2:10PM The Future of Lahontan Cutthroat Trout in Great Basin: Back to the Basics
  Jason Dunham
In the past 25 years, a large body of research has provided unprecedented insights into the population ecology of Lahontan cutthroat trout living in small streams of the Great Basin. Thousands of observations of fish populations have been successfully assembled into powerful statistical models that project population dynamics with interfaces that are easily accessible to end users. As this body of knowledge has emerged, there has been a collective realization that a critical gap in understanding streams themselves. Patterns of thermal heterogeneity, stream flows, and flow permanence (drying) in space and time remain poorly elaborated. Further, understanding how this heterogeneity plays into future responses to drought, fire, and other forms of climate responses is limited. Several studies are now underway to address this gap. Early findings from this work will be summarized, along with implications for understanding the future of Lahontan cutthroat trout – and the future of streams themselves.
2:30PM Moving Mountains and Making It Rain: Enhancing Riparian Resiliency with Grazing Management and Beaver
  Kurt Fesenmyer, Daniel Dauwalter, Carol Evans, Todd Allai
To enhance habitat for Lahontan cutthroat trout and increase the resiliency of riparian and aquatic habitats, land managers are increasingly using alternative grazing strategies, beaver management, or beaver dam surrogates as low-effort, low-expense restoration approaches. To evaluate the effectiveness of these approaches, we used archives of satellite and aerial imagery spanning three decades to characterize riparian vegetation productivity and document beaver dam occurrences, then estimated vegetation productivity relative to land management associated with livestock grazing and beaver dam densities while accounting for climate and wildfire. After controlling for stream characteristics, we demonstrate a positive response of riparian area vegetation to conservation-oriented grazing approaches and livestock exclosures, extensive beaver dam development, increased precipitation, and lack of wildfire. We show that livestock management which emphasizes riparian recovery objectives can be an important precursor to beaver activity and describe 11–39% increases in floodplain vegetation productivity where conservation-oriented grazing approaches or livestock exclosures and high beaver activity occur together on low-gradient sites. We describe how land management decisions can therefore potentially confer resiliency to riparian areas under changing and variable climate conditions, and discuss the social and management conditions which enabled restoration.
2:50PM Refreshment Break
3:20PM Water Transactions As a Conservation Tool for Lahontan Cutthroat Trout
  Laura Patten
Decades of reduced freshwater inflows for agricultural use in the Walker Basin have resulted in poor water quality conditions (increased salinity and dissolved solids) that have led to the extirpation of fishes and reduced habitat for migratory waterfowl within Walker Lake. The health of this terminal lake and the economy of the societies that live in Walker Basin is determined by the upstream hydrologic connectivity and water quality conditions within the Walker River. The Walker Basin Conservancy, in partnership with local communities, private landowners, water managers, tribes and a variety of public agencies supports the voluntary sale and lease of water and related interests, as well as associated conservation, stewardship and research activities to increase instream flow to Walker Lake as well as protect water quality. To date, the Walker Basin Restoration Program, as managed by Walker Basin Conservancy, has acquired up to 43 percent of the water needed (and expended $82 million) to restore Walker Lake and River. Here we discuss the history of the acquisition program, status and milestones related to acquisition including court decisions, progress in field work to restore the riparian corridor for cutthroat trout and improved recreational benefits.
3:40PM Adaptive Management of Lahontan Cutthroat Trout in Fallen Leaf Lake, California
  Jason Smith, Stephanie Byers
Lahontan Cutthroat trout (LCT) recovery planning and implementation in Fallen Leaf Lake, CA, has been ongoing by the U.S. Fish and Wildlife Service in collaboration with State, Federal and Tribal agencies and Universities since 2002. Reintroduction of LCT in Fallen Leaf Lake was initiated as a template for research into the conservation measures needed to re-establish a self-sustaining lake form of LCT that could be applied in Lake Tahoe. The Lahontan National Fish Hatchery Complex (LNFHC) has been reintroducing Pilot Peak LCT into historic habitat in Fallen Leaf Lake, CA, a challenging reintroduction effort in the face of nonnative salmonid predators due to the current nonnative fish assemblage (lake, brown, kokanee, and rainbow trout) that are well established. This ongoing project has shown success, however, LCT is not yet self-sustaining. Beginning in 2008, efforts to create a niche for reintroduced Pilot Peak LCT began by suppressing lake trout, stocking production fish in complex habitat, and utilizing the thermocline to provide thermal refuge from predators. Using an adaptive management approach, we documented overwintering survival of reintroduced Pilot Peak LCT, demonstrated that Pilot Peak LCT provide a native, near-shore fishery, and that these fish are spawning in Glen Alpine Creek.
4:00PM Answering the Threat of Non-Native Trout to Lahontan Cutthroat Trout: Choice of Tools–Manual and Chemical
  David Lentz, William Somer, Chad Mellison, Jason Barnes, Cody Byrne, Sarah Muskopf, Jason Smith, Michael Starr
In addition to impacts to the quantity and quality of habitat the presence of non-native trout is one of the biggest threats for Lahontan Cutthroat Trout (LCT) recovery. LCT have been displaced from more than 90 percent of their historic habitats. Earlier recovery efforts have resulted in many expanded and new LCT populations, typically by eradicating non-native trout with chemical treatment projects using piscicides. Later, increasing social, political, and regulatory complications have made planning and implementing chemical treatment projects more complex and challenging, especially in California. Recently, managers have opted with greater frequency to suppress and remove non-native trout using manual/mechanical methods, typically electrofishing, netting , and trapping. We review several manual removal/suppression projects across the LCT range alongside the characteristics of successful non-native trout manual removal efforts in the West. Non-native removal project success is influenced by many factors including available resources, removal methodology and time-frame, and habitat size and complexity. We review factors and considerations managers face in decision-making regarding choosing manual/mechanical removal efforts or chemical treatment projects to gain insight for LCT managers and pursuit of recovery objectives.
4:20PM A Collaborative Success; How Multiple Agencies and Private Organizations Can Work Together for the Benefit of a Threatened Species.
  Kris Urquhart
Prior to 2016, the Walker Basin strain of Lahontan cutthroat trout (LCT) was limited to six small fluvial populations existing in the headwaters of the Walker Basin in California. The Walker Basin Recovery Implementation Team concluded that expanding the range was prudent due to continued drought and non-native trout impacts on three of the six remaining populations. During October 2016, 343 LCT were released into Cottonwood Creek in the Wassuk Mountain Range on the western shore of Walker Lake, Nevada. The range expansion of Walker Basin LCT into Nevada represented the culmination of an eight year project by numerous federal, state, and private partnerships that included the United States Fish and Wildlife Service, California Department of Fish and Wildlife, University of Nevada, Reno, University of California, Davis, Trout Unlimited, Department of Defense, Hawthorne Army Depot, Nevada Department of Wildlife, and numerous local individuals with interest in LCT recovery.
4:40PM Monitoring the Sport Fisheries of Lake Tahoe, Donner Lake, Stampede Reservoir, and Echo Lake(s) Using Citizen Science As a Means of Low-Cost Data Collection.
  Michael Mamola
The current state of the recreational sport fisheries in the Truckee River drainage is of great interest to fishery managers. Capturing angling information in a low-cost manner can be achieved by partnering with citizen scientists and other volunteer members of the public. As a means of collecting data from anglers in 2018, we developed a method involving the distribution of angler effort / catch record books to a sub-set of area anglers and professional guides on Lake Tahoe, Donner Lake, Stampede Reservoir, and Echo Lake(s). By working with these anglers and their angler effort / catch record books, fishery managers were able to determine species composition and strain of fish caught, as well as catch rates and length frequencies for Lake Trout, Brown Trout, Brook Trout, Rainbow Trout, Kokanee, and Lahontan Cutthroat Trout found in Lake Tahoe, Donner Lake, Stampede Reservoir, and Echo Lake(s).

 
Organizers: David Lentz, Chad Mellison, Sean Vogt
 

Symposium
Location: Atlantis Hotel Date: October 3, 2019 Time: 8:00 am - 5:00 pm