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Overview
Basics
Basics
On 9/6/2023, invasive New Zealand mudsnails (NZMS) were discovered in areas off the South Shore by divers conducting aquatic invasive plant monitoring. Following rapid response protocols under the federally approved Lake Tahoe Aquatic Invasive Species Management Plan, TRPA convened an incident team comprised of staff from TRPA, Tahoe RCD, and partner experts and began rapid response actions: delineation, tracking spread, updating prevention procedures, expanded outreach and education, and researching management options. A technical advisory committee was formed to provide expertise. Actions to track and prevent spread have been incorporated into AIS program protocols.
Implementation
2023
2023
2025
$550,000
Emily Justice (ejustice@trpa.gov)
01/12/2024
02/12/2025
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| Location Information | Location Notes |
|---|---|
Organizations
Organizations
EIP Details
EIP Basics
EIP Basics
Performance Measures
Expected Performance Measures
Expected Performance Measures
| Watercraft Inspections for Invasive Species | [Action Taken: Watercraft Decontaminated], [Invasive Species Detected: Other (fauna)] | number | |
| New Invasive Species Locations Detected | [Invasive Species Type: Aquatic] | number | |
| Acres of Invasive Species Inventoried | [Invasive Species Type: Aquatic] | acres |
Reported Performance Measures
Reported Performance Measures
| Acres of Invasive Species Inventoried | ||||
|---|---|---|---|---|
| 2023 | 2024 | Total | Units | |
| Invasive Species Type | ||||
| Aquatic | 3,200 | 4,087 | 7,287 | acres |
| Total | 3,200 | 4,087 | 7,287 | acres |
Funding
Expected Funding
Expected Funding
$550,000
$250,000
$300,000
| Total | |||
|---|---|---|---|
| Lake Tahoe Restoration Act (TRPA) | $150,000 | $150,000 | $0 |
| U.S. Fish and Wildlife Service (USFWS) | $100,000 | $100,000 | $0 |
| Grand Total | $250,000 | $250,000 | $0 |
Reported Expenditures
Reported Expenditures
| Total | 2024 | 2023 | |
|---|---|---|---|
| Lake Tahoe Restoration Act | $226,208 | $76,208 | $150,000 |
| SB630 Funds | $26,700 | $26,700 | $0 |
| Tahoe Fund | $56,000 | $56,000 | $0 |
| U.S. Fish and Wildlife Service | $100,000 | $100,000 | $0 |
| Grand Total | $408,908 | $258,908 | $150,000 |
Photos
Invasive New Zealand mudsnails on algae in Lake Tahoe.
(Timing: During) (~1,363 KB)
Invasive New Zealand mudsnails from Lake Tahoe under a microscope.
(Timing: During) (~534 KB)
New Zealand mudsnail size is about the size of a grain of rice.
(Timing: During) (~658 KB)
Size of invasive New Zealand mudsnail compared to a dime.
(Timing: Unknown) (~62 KB)
Clean Drain Dry Poster for non-motorized recreators. Created 2024
(Timing: During) (~250 KB)
Roving Inspector educating beach goers and paddlers.
(Timing: During) (~3,821 KB)
eDNA collection
(Timing: During) (~579 KB)
eDNA collection
(Timing: During) (~265 KB)
Locations of CDFW visual survey transects for NZMS.
(Timing: During) (~756 KB)
eDNA sampling locations 2024.
(Timing: During) (~774 KB)
2023 Grid Survey for New Zealand mudsnail.
(Timing: During) (~868 KB)
2024 Grid survey for New Zealand mudsnail.
(Timing: During) (~863 KB)
Other Details
Watersheds
No watersheds set for this project.
Threshold Categories
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Maintain healthy habitats and ecosystems for native fish.
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Maintain healthy nutrient and algal levels in the Lake and tributaries.
Local and Regional Plans
No Local and Regional Plans set for this project.
Related Projects
Related Projects
No Related Projects set for this project.
External Links
No external links entered.
Notes
Notes
| 01/10/2025 10:13 AM | Emily Justice | In 2024 a variety of delineation, monitoring and prevention activities occurred as described below. DELINATION AND MONITORING - The point grid survey from 2023 was repeated and expanded further up the east shore to Round Hill Pines. Three new deep dive transects (65-150 feet) were added in addition to the three surveyed from 2023. Minimal spread of NZMS to the east was observed with furthest population found off of Nevada Beach. NZMS again found as deep as 150' in half of the deep dive transects at "sparse" densities. This work was led in partnership between TRPA and Tahoe RCD. - Point surveys (via aquatic weed rake, not divers) were conducted throughout the Tahoe Keys Homeowners Lagoons and Tahoe Keys Marina, including both East and West boating channels. This effort was slightly expanded to provide finer detail in areas that detected NZMS in 2023. No spread of NZMS was observed in the West/Homeowner Lagoon side; one new site further south into the East/Marina Lagoon side was observed. This work was led by TRPA. - eDNA sampling in tributaries. 280 samples were collected from 30 high priority tributaries throughout the Lake Tahoe Basin. No NZMS were detected in any of the samples. This effort was led by TRPA, supported by CTC, TERC, Lahontan Water Board, NDEP, TWSA, Tahoe RCD, and the League. Funding provided by USFWS. Coordinated effort with in-kind costs provided by others that were not able to be fully quantified. - Site Assessment methodology was expanded to include surveying for NZMS and all 26 sites that received site assessments (sometimes multiple assessments) in 2024 were also surveyed for NZMS. Of these sites, five locations detected NZMS and one of those sites was not detected in other survey techniques. Site assessments are conducted by Tahoe RCD. - Visual shoreline surveys were conducted at 15 locations along the California side of Lake Tahoe. No NZMS were detected at any of the sites. This effort was led by CDFW. PREVENTION - To better prevent the spread of NZMS around or outside of Lake Tahoe, the Watercraft Inspection Program reinforced requirements to Clean, Drain, Dry (CDD) upon exit from Lake Tahoe. Launch ramp staff facilitated each user with pulling their drain plug, lowering and draining drive units, and clearing the hull and trailer of plant material in order to receive an inspection seal. Upon reentry to Lake Tahoe, ramp staff confirmed the absence of plant material and that all systems had been drained (ballasts, fish wells, etc.). They also informed users to “Spill where you Fill” to encourage ballast tanks and fish wells to be emptied on-water in the same area they were filled to avoid the spread of NZMS around the lake. - An additional CD3 waterless cleaning station was deployed to facilitate non-motorized users with Cleaning, Draining and Drying their vessels before and after usage in Lake Tahoe. - Two Roving Inspectors were hired to educate and facilitate non-motorized users at heavily trafficked access points around the lake. They performed inspections, trained Tahoe Keepers, facilitated use of CD3 stations, and informed users around the lake, reaching out to the community and increasing visibility and accessibility. - The Tahoe Keeper Fleet program was re-invigorated to engage with non-motorized rental companies around the Lake. Although not yet fully activated, public and private rental companies around the lake are encouraged to prevent the use of their fleet between local waterbodies to avoid the spread of NZMS within the basin. - Tahoe Keepers put out a new certification video that included ways to prevent the spread of NZMS, and raised the number of dry days required to CDD, from 5 to 7 days. - Watercraft Inspections also increased decontamination requirements for vessels coming from NZMS infested waters in the last 5 days to the last 7 days. In addition, the anchor and anchor locker are the most likely to transport NZMS, and were added as a mandatory decontamination for every vessel coming from NZMS waters. The NZMS Incident Team will continue to collaborate with experts to develop next steps for 2025. |
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| 01/08/2025 12:11 PM | Emily Justice | Note that the Acres of AIS Inventoried metric only includes the activities which can be measured in acres. The metric does not include the following monitoring actions for which we currently do not have a way to calculate acreage: Tahoe Keys Rake Point Sampling (58 samples) and eDNA (280 samples). | ||
| 03/15/2024 8:35 AM | Emily Justice | Note that the Acres of AIS Inventoried metric only includes the 3200 acres of the Grid Survey which spanned from Eagle Point to Nevada Beach (approx. 10 miles). Metric does not include the following monitoring actions for which we do not currently have a way to calculate acreage: - Rapid Assessment line survey - Lakewide transects: 109 transects of varying lengths - Tahoe Keys Rake Point Sampling: 31 composite samples - eDNA: 36 samples |
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| 01/12/2024 12:37 PM | Emily Justice | The incident team and the Watercraft Inspection Program took quick action to modify the inspection and decontamination protocols to address the discovery. In addition, the team began planning for the 2024 boating season. Outreach actions included alerting partners and planning to bolster the non-motorized users and anglers, including social media, trainings and signage. In 2023, the incident team worked to delineate the extent of NZMS infestation by various methods described below: - Rapid assessment line surveys near the area where NZMS were first identified - A point grid survey spanning from Eagle Point to Nevada Beach, including three deep water (150 feet) transects - The Lakewide Transect AIS Monitoring methodology was adapted to capture NZMS absence or presence. - Additional point surveys (via aquatic weed rake, not divers) were conducted throughout the Tahoe Keys Homeowners Lagoons and Tahoe Keys Marina, including both East and West boating channels. - Environmental DNA (eDNA) water samples were collected from 36 sites along the Upper Truckee River, Trout Creek, Lake Baron, and Sawmill Pond in South Lake Tahoe. To summarize the results of the delineation work outlined above, NZMS were found in the Lake from the east end of Pope Marsh to Ski Run, with a small satellite population at Camp Richardson's. NZMS were observed at depths ranging from 4-150 feet. NZMS were not found at any sites in the Lakewide transect surveys besides within the infested area defined by the grid survey. In the Tahoe Keys, both the East and West boating channels were positive for NZMS but the rest of the sampling sites were negative. All eDNA samples collected were negative for NZMS. The grid survey, Lakewide transect survey, Tahoe Keys point sampling, and expanded eDNA sampling will occur in 2024. |