An investigation of aquatic invasive species in pristine sites in the Greater Yellowstone Area

Science Center Objects

Aquatic invasive species (AIS) are aquatic organisms that move into ecosystems beyond their natural, historic range and cause severe and irreversible damage to the habitats they invade. Most AIS arrive as a direct result of human activity, such as boating and angling. The threat of AIS introduction is especially high in the Greater Yellowstone Area, as humans from all over the world come to see the natural features and wildlife of the region. In fact, over 3.8 million visitors came to Yellowstone National Park in 2015 alone. Because of the large risk posed by this magnitude of human activity, the Aquatic Invasive Species Subcommittee of the Greater Yellowstone Coordinating Committee (GYCC) has made AIS early detection efforts a high priority. Early detection increases the possibility of eliminating or controlling AIS and minimizing their impacts to Greater Yellowstone habitats.

As AIS introductions are related to human activities, Greater Yellowstone sites adjacent to roads that receive high volumes of boating and angling use have been prioritized for early detection monitoring. Consequently, we know little about the AIS status of lower risk sites in more pristine waters. These lower risk sites are important because they comprise the headwaters of the GYA. As AIS are introduced into headwater habitats they have the potential to quickly spread downstream. To address this data gap, the GYCC AIS subcommittee requested assistance with developing AIS early detection protocols specific to these lower risk, remote waters. Key requirements for these protocols were that they can be effectively executed by minimally trained personnel, used to make inferences about the AIS status of hundreds of square miles of lower risk sites in the Greater Yellowstone, and that it provides AIS status of sites that are of management concern.

 

Filtering water for eDNA sample collection in Yellowstone National Park between Lewis and Shoshone Lakes.

Filtering water for eDNA sample collection in Yellowstone National Park between Lewis and Shoshone Lakes.Public domain

Approach

To meet these stated needs, we used management expert knowledge and a Generalized Random Tessellation Stratified (GRTS) survey design to select 48 sites for early detection monitoring in the Bridger-Teton National Forest, Yellowstone and Grand Teton national parks. For Grand Teton National Park, we provide an example of how invasion risk posed by human activity can be used to dictate site selection in the GRTS framework. In Year 1, we conducted rapid assessment surveys for AIS and corroborated these results with environmental DNA testing for 4 AIS of management concern:  New Zealand mudsnails, rusty crayfish, dreissenid mussels, and Eurasian watermilfoil. In Year 2, we refined these protocols to ensure that they could be effectively executed with minimal training, supplies and equipment. The only targeted AIS detected in our 48 sites were New Zealand mudsnails in the Snake River, near the South Entrance of Yellowstone National Park.

The first objective of the project was to develop a probabilistic framework to guide GYA managers’ identification of lower use waters to be monitored during early detection surveys. We encourage managers to use a Generalized Random Tessellation Stratified (GRTS) survey design protocol of Griswold and Larsen (2011) to identify the sites that will be surveyed. The second objective was to develop a rapid assessment method for early detection of AIS. We tested the efficiency of 3 types of rapid assessment methods in 10 bodies of water, from each area (GTNP, YNP, and Bridger-Teton NF) during 2014 and 2015. At each site we conducted environmental DNA (eDNA) sampling and visual surveys. Results conveyed that early detection protocols should focus on filtering water to capture DNA from target AIS. Filtration sampling is limited to only target fish and provides limited information when considering abundance, diversity, ect. For these reasons, we recommend the use of visual surveys targeting 4 AIS of concern in the GYA: New Zealand mudsnails, rusty crayfish, dreissenid mussels, and Eurasian watermilfoil. These species occur in habitats that are associated with other invaders so theoretically visual survey protocols dedicated to these 4 taxa will help expose other AIS.