Aquatic invasive species (AIS) are non-native organisms that threaten the abundance and diversity of native organisms in Lake Tahoe. Controlling and eradicating AIS in the Lake Tahoe Region is a top priority of the Lake Tahoe Environmental Improvement Program (EIP). The standard establishes the goal that all aquatic invasive plant infestations in Lake Tahoe be in the surveillance management category.

Status

Threshold is 100 percent of sites in surveillance. In 2023 there were 35 aquatic invasive plant infestations in Lake Tahoe,12 of which (33 percent of sites) met the threshold standard of being in surveillance. For the purposes of evaluating the threshold standard, the Lake Tahoe Aquatic Invasive Species Coordinating Committee defined an infestation as "active" if control requires more than one day for a two-diver team (20 diver hours) per season to treat with hand pulling. Sites in the Planning or Control category are considered “active” infestations (See "about the threshold" for additional details). In 2021,there were limitations accessing projects due to COVID restrictions, Caldor Fire impacts, and a lapse funding resulting in many sites not meeting all criteria needed to remain in surveillance or control status. Planning status was initiated at that time to ensure adequate resources were allocated back to these projects in 2022.

Evaluation Map

Aquatic invasive plants control sites.

2023 Evaluation

Status
Somewhat Worse Than Target
Trend
Insufficient Data to Determine Trend
Confidence
High
View Evaluation

Applicable Standard

WQ9: No active aquatic invasive plant infestations in Lake Tahoe, adjacent wetlands, and tributaries, not including the Tahoe Keys.

Key Points

  • Between 2020 and 2023, two additional sites were moved into the surveillance category, and one site moved from planning to active control (See "about the threshold" for additional details on management categories).
  • Lake-wide aquatic plant surveys were completed in 2018 and 2023. Total submerged aquatic vegetation in 2023 was less than half the amount in 2018, likely due to higher lake levels and control work.
  • Aquatic invasive plants are more common on the south shore.
  • Several small infestations throughout Lake Tahoe have been promoted to surveillance, allowing partners to focus on significantly larger and more complex infestations such as Taylor Tallac and the Tahoe Keys lagoons.

About the Threshold

Maintaining the biological integrity of Lake Tahoe’s nearshore environment is a longtime goal of resource managers in the region and has been set forth in a variety of planning documents. Submerged aquatic vegetation is an important biological component within Lake Tahoe’s nearshore context. Knowing the status of submerged aquatic plant populations at Lake Tahoe has become increasingly important to nearshore managers due to the introduction and spread of invasive species such as Eurasian watermilfoil (Myriophyllum spicatum) and curly-leaf pondweed (Potamogeton crispus). Aquatic invasive plants when left unchecked can impact water quality, fish and wildlife habitat conditions, recreational fishing, human and animal health, vessel navigation, and the recreation values of water bodies. The threshold standard establishes a goal for aquatic invasive plant infestations in Lake Tahoe and associated areas. The standard establishes the goal that all aquatic invasive plant infestations in Lake Tahoe (not including the Tahoe Keys, which has a separate standard) be in the surveillance category. The goal aligns with the management categories that are utilized by the Lake Tahoe Aquatic Invasive Species Coordinating Committee and conveys the reality of long-term management of aquatic invasive species. Due to aquatic invasive plants’ proclivity towards spreading and establishing new infestations through fragmentation throughout connected waterbodies, all completely treated AIP sites are at risk of re-establishment if there is source of AIP fragments within Lake Tahoe. The goal acknowledges that because of this risk, complete eradication is unlikely, and control will likely require continued surveillance and vigilance. The threshold standard formally adopts the phase one vision laid out in the Lake Tahoe Region AIS Action Agenda.
Non-native species have been both intentionally and unintentionally introduced to Lake Tahoe over the last 150 years. Habitat modification such as channelization and modification of the Upper Truckee Marsh for the Tahoe Keys also created micro-environments within the lake that may be more suitable for colonization by AIS. Climate change further threatens to alter the lake’s physical environment, with the potential for making further AIS establishment more likely. Three management categories are used to evaluate the status of individual infestations. Planning – Active infestation. Active planning and procurement of funds to treat. Site Assessments, coordination with landowners, Containment, marina-led maintenance treatment, or pilot methods testing projects may be implemented. Active control methods (barriers, diver-assisted suction, or UV-C) will likely be needed to treat this site. Control – Active infestation. Active control methods (barriers, diver-assisted suction, or UV-C, site preparation, or methods testing) were implemented throughout the season. Also includes first-time or previously treated control sites that only required hand removal to maintain the weed-free status. Surveillance - Previously treated control site, not an active infestation. Throughout one season, no more than 20 diver hours over the expected surveillance effort was required at this site to maintain weed-free status. Also includes sites where consecutive surveys over have revealed no detections.

Delivering and Measuring Success

EIP Action Priorities

EIP Indicators

Example EIP Projects

Local and Regional Plans

  • Aquatic Invasive Species Action Agenda 2021-2030

    The Lake Tahoe Region Aquatic Invasive Species Action Agenda 2021-2030 implements a well-funded, comprehensive, robust, simultaneous, science based, and aggressive suite of AIS control actions.

Monitoring Programs

Rationale Details

Somewhat Worse Than Target. Not in attainment. There are 35 aquatic invasive plant infestations in Lake Tahoe. In 2023, 12 of the sites were in surveillance, 12 were in planning, and 11 were in control. For the purposes of evaluating the threshold standard, the Lake Tahoe Aquatic Invasive Species Coordinating Committee defined an infestation as "active" if control requires more than one day for a two-diver team (20 diver hours) per season to treat with hand pulling. Sites in the Planning or Control category are considered “active” infestations.

A separate threshold standard applies to the Tahoe Keys infestation.

Insufficient Data to Determine Trend. Trend not assessed. The standard was adopted in 2024.

Confidence Details

High. Sites are surveyed regularly and the methods for determining status are detailed and objective.
N/A. Trend not assessed.
High.

Additional Figures and Resources

No photos available.


No documents available.