Invasive Mudsnails Detected at Lake Sonoma Fish Hatchery

Fri, 13 Oct 2023 10:36:38 GMT

The California Department of Fish and Wildlife (CDFW) and partners have confirmed the presence of New Zealand mudsnails (NZMS) at Warm Springs Fish Hatchery near Lake Sonoma. While NZMS have been detected in other portions of the watershed, this is the first confirmed detection at Warm Springs Hatchery.

NZMS were detected in an intake pipeline and an aeration pond during a regularly scheduled quarterly hatchery survey this summer. Since the detection, scientists have conducted surveys in about 75 percent of Coho-bearing streams in the watershed and have not observed NZMS presence beyond previously known locations. Warm Springs Hatchery operates production and release programs for Coho salmon (a federal and state-listed endangered species) and steelhead (federally listed threatened species). The NZMS surveys have focused on stocking locations for these fish species, which are conducted mostly in Russian River tributaries in the lower basin.

“The detection levels so far have not been alarming, but we want to do everything we can to minimize the spread,” said CDFW North Central Regional Manager Morgan Kilgour.

Dense populations of NZMS can displace and out-compete native species; they may consume up to half of the food resources in a stream and have been linked to reduced populations of aquatic insects, including mayflies, caddisflies, chironomids and other insects important to trout and salmon.

Invasive NZMS were first discovered in California in 2000 in the Owens River. It is believed that the species was introduced to western rivers through shipments of live sportfish, but subsequent spread is likely due to recreational activities. Dry Creek, which flows by Warm Springs Hatchery, has previously been identified as positive for NZMS. The source of the recent NZMS detections is unknown, but it is suspected that the snails came to the hatchery via its source water of Lake Sonoma.

The U.S. Army Corps of Engineers (USACE) operates the Russian River Coho Salmon Captive Broodstock Program at Warm Springs Fish Hatchery, and contracts with CDFW to operate its steelhead program. In addition to the surveys, CDFW has increased biosecurity measures at the hatchery.

The hatchery will continue to operate its Coho and steelhead programs. CDFW is working with USACE and the National Oceanic and Atmospheric Administration (NOAA), which permits the hatchery, to determine if any changes in Coho release protocols are needed given the detections.

“NOAA Fisheries fully supports CDFW and the USACE’s efforts to minimize the risk of further spread of aquatic invasive species such as NZMS within the Russian River and other watersheds that provide critical habitat for listed salmon and steelhead,” said Robert Coey, north central coast supervisor in NOAA Fisheries’ West Coast region.

Boaters, anglers and others who visit the Russian River watershed are asked to decontaminate equipment and follow the “clean, drain and dry” directive with all equipment used in the river:

If you wade, freeze waders and other gear overnight (at least six hours).
After leaving the water, inspect waders, boots, float tubes, boats and trailers or any gear used in the water.
Remove any visible snails with a stiff brush and follow with rinsing. If possible, freeze or completely dry out any wet gear.
Never transport live fish or other aquatic plants or animals from one waterbody to another.

Additional information about stopping the spread of NZMS can be found on CDFW’s California’s Invaders: New Zealand Mudsnail web page.

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Media contact:
Steve Gonzalez, CDFW Communications, (916) 804-1714

Invasive New Zealand Mudsnails Discovered In Lake Tahoe

Thu, 21 Sep 2023 14:08:26 GMT

Anglers, Residents and Visitors Urged to Help Prevent Further Spread

The California Department of Fish and Wildlife (CDFW) was informed by the Tahoe Regional Planning Agency (TRPA) that divers monitoring for aquatic invasive species in Lake Tahoe detected invasive New Zealand mudsnails (Potamopyrgus antipodarum) in areas off the South Shore of Lake Tahoe. New Zealand mudsnail samples were subsequently positively identified by experts within CDFW and an outside genetics lab. This is the first time the species has been detected in Lake Tahoe.

New Zealand mudsnails (NZMS) are tiny, aquatic snails that reach, on average, up to 4-6 millimeters long. Despite their small size, NZMS are a highly problematic aquatic species. Dense populations can displace and outcompete native species, sometimes by consuming up to half the food resources in the waterway. The snails have been linked to reduced populations of aquatic insects, including mayflies, caddisflies, stoneflies, and other insects upon which trout and salmon populations depend.

“This is a significant detection and one we’re treating with the utmost seriousness and urgency to determine the extent of the infestation and prevent any further spread within the Lake Tahoe watershed,” said Colin Purdy, Environmental Program Manager for CDFW’s North Central Region, which encompasses the California portion of Lake Tahoe and the surrounding areas of Placer and El Dorado counties. “We greatly appreciate the communication, collaboration and rapid response coordinated so far by TRPA and the Tahoe Resource Conservation District. It will take a coordinated commitment by all the entities that serve the Tahoe Basin as well as the public to prevent the further spread of these invasives in a lake and a watershed that’s cherished around the world.”

CDFW urges anglers, boaters, visitors and locals to “clean, drain and dry” all recreational items and fishing gear, which generally means anything that has gotten wet. It is important to leave any stream or lake water, debris and organic plant matter at a recreational site in order to prevent the further spread of the snails.

Once NZMS are established in a new habitat, they are impossible to eradicate without damaging other components of the ecosystem. Boaters, anglers and others who may visit any body of water, within or outside of infested areas, are asked to decontaminate their equipment and follow the “clean, drain and dry” best practices for all equipment and clothing used in a waterway. Those best practices include:

If you wade, freeze waders, wading boots and other gear overnight (at least six hours, though 24 hours is recommended).
After leaving the water, inspect waders, boots, float tubes, paddleboards, kayaks or any gear used in the water. Leave all water and debris at the site that you exited.
Additionally, remove any visible snails with a stiff brush, clean off soils and organic material, and follow this by rinsing at the site, preferably with high-pressure hot water.
It is critical to completely dry out gear for a minimum of 24 hours.
Never transport live fish or other aquatic plants or animals from one body of water to another.

CDFW scientists are also in the process of developing and implementing plans for sampling in waterbodies around the Tahoe Basin to better define the geographic range of this new population. Sampling areas will include high-traffic areas, boat launches, access points, coves, inlets and outlets, and side channels. To date, the snails have not been identified at any of these surrounding waterbodies; however, they have been detected in several waterbodies (lakes and river systems) throughout California and in neighboring states. Decontamination procedures are being implemented by field crews working on Lake Tahoe and surrounding waterbodies.

 How Can You Help?

Start with the following:

Report an invasive species sighting online to CDFW.
The best way to avoid spreading these non-native snails is to clean and decontaminate fishing gear, recreational equipment, and watercraft between waterbodies. Please refer to CDFW’s Aquatic Invasive Species Decontamination Protocol 2022 (PDF).

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Media Contacts:
Leslie Alber, CDFW North Central Region, (530) 708-1745
Peter Tira, CDFW Communications, (916) 215-3858

CDFW News

Invasive Mudsnails Detected at Lake Sonoma Fish Hatchery

Invasive New Zealand Mudsnails Discovered In Lake Tahoe