Watershed restoration efforts often aim to maintain or increase connectivity because it can increase migration among populations, genetic diversity among groups of connected populations, and riverscape processes that maintain ecosystem health. These outcomes, in turn, can increase the evolutionary potential of populations to respond to future disruptions caused by human disturbance, climate change, and fire. However, increasing aquatic connectivity can  also increase the prevalence of invasive species that present competition, predation, and/or hybridization risks to endemic species (i.e. native species that are localized to a particular area). Invasive species pose a significant threat in watersheds with mixed ownership given the mosaic of different monitoring, management, and stewardship practices that are often present. 

Photo Credit

Alexandra Fraik

The Teton River at sunset

This project will advance our ability to efficiently detect, prevent, and eradicate invasive species from highly modified riverscapes. Our research team will do this by leveraging multidisciplinary tools to: 

1. Characterize species’ distributions;
2.  Identify barriers to gene flow;
3. Determine the role that land stewards’ actions may play in maintaining these barriers;
4. Simulate the efficacy of different management strategies for removing and mitigating invasive species.

We are implementing this study in two adjacent river systems that are similarly impacted by high levels of human modification and invasion of non-native salmonid species. These watersheds have headwaters in national forests with pristine intact habitat, but they have significant down river habitat modification and disturbance. Both river basins are experiencing invasion from rainbow trout (Oncorhynchus mykiss), brown trout (Salmo trutta), and brook trout (Salvelinus fontinalis), and are historic strongholds for the endemic Yellowstone cutthroat trout (Oncorhynchus clarkii bouvieri). Each of these invasive species have distinct introduction histories, migration propensities, and ecological requirements. As a result, their prevalence and population dynamics vary, posing different threats to the endemic trout and overall ecosystem health. 

Objectives 

Throughout this work, we will investigate how variation in riverscape stewardship and connectivity impacts invasive species’ distributions, population dynamics, and interactions with a species that is endemic to the Teton and Salt River basins in Idaho and Wyoming, USA. This research will improve our ability to detect invasive species, identify key sites for eradication, and forecast at-risk waterways to prevent future invasions.

Photo Credit

Alexandra Fraik

The Teton River flows through a forest

• Objective I: Ecological factors. Quantify the distribution, occupancy, and seasonal habitat use of both endemic and invasive salmonid fishes in the Teton and Salt River basins.
• Objective II: Genetic factors. Identify how landscape features, geographic distance, restoration activities, and environmental stressors promote or limit gene flow among the four salmonid species.
• Objective III: Social factors. Create a working group of stakeholders from each basin to develop scenarios of stewardship, management actions, and infrastructure modifications that could be used to mitigate and eradicate invasive species in conjunction with mental modeling exercises.
• Objective IV: Integration. Incorporate ecological (Obj. I), genetic (Obj. II), and social (Obj. III) results in an integrative model to make predictions and identify preventative measures for future invasions in the river basins.

Taken together, this research will provide a roadmap for riverscape- and landscape-scale invasive species removal efforts. Results from ecological (Obj. I) and genetic (Obj. II) analyses will allow us to detect where species occur across the riverscape and what environmental features influence their connectivity and distribution. Species-specific assessments of which riverscape features promote gene flow and genetic diversity of invasives will allow us to make predictions for where they will establish next.  Understanding the social factors (Obj. III) that may contribute to invasive species’ existence and persistence will inform the range of collaborative management actions that could mitigate these species across the riverscape. The combination of these results will enable us to identify key locations for restoration to improve overall habitat quality for endemic species and remove invasive species strongholds. Our collaborative work with local stakeholders and stewards to gather data, inform our models and develop predictive tools relevant to restoration decisions will improve ecological health of watersheds.

Expected Project Results 

1. Assessments of fish population health and diversity. This work will provide critical assessments of fish population health and diversity that will identify potential ways forward for collaborative management of the Salt and Teton River basins. 
2. Improved invasive species detection, prevention, and eradication on both federal and non-federal lands as a result of collaboration. This project will leverage existing monitoring and restoration projects, and will engage in partnerships with Friends of the Teton River, Wyoming Game and Fish, Idaho Department of Fish and Game, the Caribou-Targhee National Forest, academic partners, and private landowners, among others. A working group composed of private, state, federal, tribal and NGO partners will meet throughout the course of the project. 
3. Probabilistic maps of future invasion potential across western riverscapes. We will use new, emerging technologies in molecular, ecological, and social sciences to assess the extent, interactions, and impacts of non-native salmonid invasion on native salmonids in both rivers. Ultimately, we will integrate these results into a model to map the probability of future invasion for these species across riverscapes in the West. 
4. An assessment of restoration management actions. Drawing on historical records of management, ecological disturbance, and fire regimes from our partners, we will determine the scope of possible restoration management actions. We will then simulate and assess the impacts of these restoration actions to determine their efficacy in eradicating invasives and improving overall watershed condition. We will work with partners and stakeholders to make defensible management decisions that reduce the impacts of invasive species, improve ecosystem health, and support fish passage across the study watersheds. 
5. Scientific advances in the fields of genetics, modeling, and data integration. The integration of eDNA surveys with population genetic data to generate and integrate species distribution models with riverscape genetic models in a predictive framework has not been done to date. We will test whether the environmental and spatial processes that govern species distributions similarly explain genetic structure and diversity. Similarly, social data reflecting stakeholder beliefs and tangible conservation actions are rarely solicited in modeling frameworks. 
6. A decision-support tool for managers. We have designed our project to create products that will be highly transferable to other systems through a public, user-friendly, computationally-efficient suite of modeling tools. An expected outcome of this project is that other watersheds facing invasive species threats and complex social considerations will be equipped with a useful, integrative tool to improve water monitoring resources and improve decision-making. This user- friendly modeling tool will be developed in collaboration with the stakeholder working group and tailored to managers’ use. While the focus of these models is invasive species detection, eradication, prevention and even prediction, one additional expected outcome is a deeper understanding of how to prioritize restoration to maximize endemic species conservation.
7. Publications, workshops, and datasets. We will generate peer-reviewed scientific publications and workshops to discuss management options as part of this study. For our management partners, we will produce key ecological, genetic, social, and collated environmental datasets.
    

Geographies and High-Risk Landscapes to be Addressed

We will conduct this research in the Teton River and Salt River basins of Idaho and Wyoming. These watersheds have headwaters in national forests with more pristine intact habitat, but they have significant downriver habitat modification and disturbance. Both river basins are experiencing invasion from rainbow trout (Oncorhynchus mykiss), brown trout (Salmo trutta), and brook trout (Salvelinus fontinalis), and are historic strongholds for the endemic Yellowstone cutthroat trout (Oncorhynchus clarkii bouvieri). Together, these two river basins encompass 990,080 acres spanning dozens of private, tribal, state and federal stewards.