CDFW News

CDFW Confirms Northernmost Detection of Golden Mussel in Port of West Sacramento

Sat, 27 Jun 2026 09:24:08 GMT

Recreation on Delta and Sacramento Waterways Comes with Responsibility to Stop Invasive Mussels’ Spread

The California Department of Fish and Wildlife (CDFW) is notifying the public and officials with the city of West Sacramento and Yolo and Sacramento counties that invasive golden mussels have been found in and around the Port of West Sacramento.

This is the northernmost detection of golden mussel since the species was discovered in the Port of Stockton in the Sacramento-San Joaquin Delta in 2024.

CDFW staff monitoring for golden mussel presence collected one mussel between the Jefferson Boulevard overpass and the west lock, and a second near the intersection of Boathouse Road and Stone Boulevard. The mussels were sent to CDFW’s genetics lab that confirmed on June 25 the specimens were golden mussel. Additional surveys around the docks in Washington Lake found additional mussels.

It is believed the golden mussels found in the Port of West Sacramento are from a source population within the vicinity. Golden mussels are harmful to aquatic ecosystems, water conveyance systems and water infrastructure.

Anyone boating or recreating on waterways around the Sacramento area, and throughout the Delta, should take precautions to stop the spread of golden mussel further upstream and overland on watercraft and equipment used in mussel-infested waters. Golden mussels attach to almost any underwater surface, including but not limited to boats, ropes, buoys and aquatic plants that entangle on anchors and trailers.

Clean, Drain, Dry — inspect your watercraft, kayak, life vests, paddles and anything that touched the water every time it is removed from a water body. Remove all debris, animals, and plants, and dispose of them in the trash. Drain all water from ballasts, bilges and live wells. Lastly, allow everything to dry until moisture is no longer present.

Through the continued efforts by boaters and others recreating on California’s waters, golden mussel can be prevented from spreading to waters not connected to the Delta.

Help CDFW monitor the state’s waters for golden mussel by reporting organisms suspected to be golden mussel to CDFW’s Invasive Species Program. Include the specific location of the observation, at least one clear close-up photograph of the organism and your contact information.

Submit reports via one of the following options:

Online at Report Golden Mussel
Via email to invasives@wildlife.ca.gov
Via telephone to (866) 440-9530

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Photo: Laboratory testing of golden mussel. California Department of Water Resources file photo

Media Contact:
Krysten Kellum, CDFW Communications, (916) 825-7120

Be Part of Protecting California’s Biodiversity During Invasive Species Action Week

Tue, 02 Jun 2026 11:08:44 GMT

Get involved to help prevent the harmful impacts of invasive species that threaten our state’s natural resources, ecology and economy during California Invasive Species Action Week (CISAW), June 6-14, 2026.

The week will offer opportunities for people across the state to come together, get their hands (or gloves) dirty and take action to protect California’s biodiversity. Educational talks are also in the lineup for those who would like to learn more about how invasives are bad news for native species, and how to identify and report invasive species.

Find the full list of CISAW events online (PDF), some which require participants to register in advance. Events planned for the week include but are not limited to:

June 6: Plant and maintain native plants and remove invasive non-native plants with the Golden Gate Bird Alliance at Pier 94 in San Francisco. The Salt Marsh Wetlands there are home to the endangered native plant California seablite, a host plant for the endangered Western pigmy blue butterfly.
June 7, 8 &14: Join the Ventura Land Trust at Harmon Canyon in Ventura where volunteers will be working to remove noxious and invasive weeds to restore the native landscape to support native plants, pollinators and other wildlife.
June 8-12: Tune in to the UC Cooperative Extension’s Lunchtime Talks webinar series, where each weekday experts will take on invasive species topics focusing on concerns and strategies for managing them.
June 9: Take the League to Save Lake Tahoe’s Eyes on the Lake Training in South Lake Tahoe, where participants will learn to identify native versus non-native aquatic plants and how to report aquatic invaders that damage Lake Tahoe’s ecosystem.
June 10: Volunteer with the Mendocino Land Trust at Navarro Point Preserve and Scenic Trail to pull invasive plant species, pick up garbage and maintain the trail.
June 11: Remove invasive plant species at Guerneville River Park with Sonoma County Parks. Invasive plants crowd out native plant communities that wildlife depends upon for food and shelter.
June 13: Learn how to identify common local invasive plants, properly remove them and help restore native pollinator habitat with the Sacramento Valley Conservancy as part of Sacramento County Regional Parks’ Family Health & Fitness Day at Camp Pollock.
June 14: Help members of the Milo Baker Chapter of the California Native Plant Society as they work in Bodega Head State Park to remove South African ice plant that was once used for erosion control along California’s coast and is now smothering our native plants.

Be a part of the effort to remove invasive species and restore wildlife habitat throughout the year by volunteering through the California State Parks Foundation and other local organizations.

Californians can also help stop the spread of invasive species by taking small, everyday actions, such as landscaping with native plants, not releasing unwanted pets into the wild and to “Clean, Drain, Dry” gear when recreating in bodies of water. The CISAW page lists simple actions Californians can take all year long while visiting natural areas, boating, fishing and even at home.

Invasive species threaten the abundance of native species through competition for resources, predation, disease transmission or by causing physical changes to the invaded habitat. Impacts of invasive species on natural ecosystems, agricultural and other developed lands, water delivery and flood protection systems, may also negatively affect human health and the economy.

The mission of CDFW’s Invasive Species Program is to reduce the impacts of invasive species on the wildlands and waterways of California. The program is involved in efforts to prevent the introduction of these species into the state, detect and respond to introductions when they occur and prevent the spread of those species that have established.

For questions or more information about CISAW contact invasives@wildlife.ca.gov.

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Media Contacts:
Krysten Kellum, CDFW Communications, (916) 825-7120
Daydre Roser, CDFW Invasive Species Program, (916) 720-1226

CDFW Research Links California’s Nutria Invasion to Pacific Northwest Population

Tue, 07 Apr 2026 10:28:13 GMT

Study Also Informs Eradication Efforts, Offers Toolkit for Future Research Worldwide

Scientists with the Wildlife Genetics Research Unit at the California Department of Fish and Wildlife (CDFW) have completed a genomic study of nutria, an invasive South American rodent, linking their 2017 discovery in Merced County to a population in central Oregon. This was the first genomic study of the semi-aquatic pest species that is harmful to wetland habitats and agriculture and has challenged control efforts of land and wildlife managers worldwide for decades.

To identify the origins of nutria in California, CDFW research scientists compared DNA of invasive nutria populations around the world. This led to building a dataset showing the genetic similarity among nutria on a global scale that will serve as a toolkit for future research. The genetic data also give insight into how nutria populations spread across a landscape — information that will inform eradication efforts and development of management strategies.

“CDFW conducts sophisticated genetics research to improve management outcomes for California’s wildlife populations,” said CDFW Wildlife Genetics Research Lead Mike Buchalski. “The results of this study additionally will benefit future national and global genetic research on nutria.”

“Genetics allowed us to narrow down the most likely source of California’s nutria population and provide land and wildlife managers with information about how these animals are spreading across the landscape,” said CDFW Research Scientist Kristen Ahrens. “We have also created a global reference dataset that others can use to compare populations and trace invasion pathways.”

Nutria were introduced to countries all over the world to be raised for their pelts at the height of the fur trade in the late 19th and early 20th centuries, including in California. When that trade collapsed nutria were set free from fur farms, leading to a limited number of feral populations on the landscape, which seemingly failed to thrive. Localized nutria eradication efforts followed, and they were ultimately declared eradicated from California by the late 1970s.

There was no sign of nutria presence in the state until 2017 when a pregnant female was found in Merced County. Unlikely that nutria could have gone undetected since eradication in the 1970s, particularly given the rapid rate of reproduction and geographic spread observed following their discovery, CDFW went to work to assess genetic variation in past and present nutria populations in California to find the origin of this recent discovery.

To compare today’s nutria with those present before eradication, historical genetic data were essential. CDFW’s Ahrens located and sampled nutria skins and skulls housed in museums and universities across California, and one unexpected source in a taxidermy nutria found at the Butte County Weights and Measures Department office. Recovering DNA from decades-old specimens allowed direct comparison of past and present maternal lineages, providing critical insight into the origins of the current invasion.

CDFW’s Nutria Eradication Program team provided tissue samples for DNA sequencing of California’s current nutria population.

For broader comparison, Ahrens obtained tissue samples from federal and state wildlife management agencies for other nutria populations in the U.S. — Louisiana, Texas, Maryland, Virginia, Oregon and Washington. Ahrens was also able to tap into publicly archived sequenced DNA from invasive nutria in South Korea, Japan and Brazil.

Comparisons showed that nutria in California today are most genetically similar to populations in central Oregon. Historical California nutria represented multiple maternal lineages, based on analysis of the museum bone and taxidermy specimens. In contrast, today’s population traces back to a single lineage, also detected in historical samples, a pattern most consistent with a recent reintroduction rather than survival of the earlier, more diverse population.

Ultimately, the genetic research suggests California’s current nutria invasion was the result of intentional reintroduction, with the original source animals likely being transported from the central Oregon population, which is prohibited by Fish and Game Code section 2118 and Title 14, California Code of Regulations section 671. Eradication efforts are now costing the state about $5 million per year.

“This study supports our long-held belief that the current invasion is the result of reintroduction rather than explosive growth of a remnant, undetected population,” said Nutria Eradication Program Manager Valerie Cook. “While we can only speculate on the ‘reasoning’ behind the reintroduction of this incredibly destructive invasive species, these findings highlight the critical importance of biosecurity inspections aimed at preventing the importation and transportation of invasive plants and animals into and within California.”

CDFW’s Nutria Eradication Program has taken 7,841 nutria in California since 2017. Eradication efforts are underway across hundreds of thousands of acres of wetland and riparian habitat in California’s Sacramento-San Joaquin Delta and Central Valley, spanning from San Pablo Bay to Kings County. Visual observation surveys, motion-detection cameras and scat-detection dogs help CDFW’s eradication team detect nutria presence for subsequent trapping efforts.

Findings of the nutria genomic study will be another valuable tool for the CDFW Nutria Eradication Program. This study demonstrates how genetics can shed light on population structure and patterns of gene flow to better understand how nutria disperse across a landscape.

The nutria genomic research took place over the past five years and was funded by the California Department of Water Resources. Research was done in partnership with the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service.

The recently published paper on the study, Population Genomic Insights Into Recent Nutria Invasion Dynamics, is available online.

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Media Contacts
Michael Buchalski, CDFW Wildlife Health Laboratory, (916) 508-1385
Krysten Kellum, CDFW Communications, (916) 825-7120

New Legislation Adds Invasive Mute Swan to List of Nongame Birds That May be Taken

Mon, 20 Oct 2025 14:19:01 GMT

State legislation signed into law earlier this month will allow invasive mute swans to be taken or possessed at any time by those with a valid California hunting license beginning January 1, 2026.

The legislation, which has a sunset date of January 1, 2031, was introduced to address the growing concerns about the spread of these destructive, non-native species throughout the state.

Mute swans now join the short list of invasive nongame birds – the English sparrow and the European starling being the two others – listed in the California Fish and Game Code, Section 3801 that can be taken at any time by licensed hunters. Landowners and lessees may also take or possess mute swans at any time without needing a hunting license or depredation permit.

Mute swans were first detected in the Suisun and Napa marshes during the California Department of Fish and Wildlife’s (CDFW) annual Waterfowl Breeding Population Survey in 2007. Since that time, they’ve expanded their range with the most current population estimate at 6,900 birds. Mute swans are regularly reported to the CDFW’s Invasive Species Program and Waterfowl Unit as they are classified as a restricted and detrimental species unlawful to import, transport or possess under the California Code of Regulations, Title 14, Section 671.

Mute swans are generally nonmigratory and present year-round. They are not protected under the federal Migratory Bird Treaty Act unlike native waterfowl species since mute swans were introduced from Europe to North America during the mid-1800s and considered highly invasive.

Mute swans are very territorial, aggressive and do not typically intermix with other wintering waterfowl. Mute swans prefer permanent and semi-permanent wetland habitat feeding primarily on submerged aquatic vegetation. These habitats are limited in California and are essential for many sensitive native species as well as for breeding ducks and other wetland-dependent birds.

AB 764 was introduced by Assemblymember Jeff Gonzalez, R-Indio, and sponsored by the California Waterfowl Association to provide additional tools to control this invasive species population. Gov. Gavin Newsom signed the bill into law October 6.

The public is encouraged to report the take or possession of any mute swan to CDFW’s Invasive Species Program online or by e-mail at invasives@wildlife.ca.gov.

More information on mute swans is available at CDFW’s Invasive Species Program web page, including a Swan Identification Sheet (PDF) to help distinguish mute swans from native tundra and trumpeter swans, which cannot be hunted, taken or possessed at any time in California.

Media Contacts:
Melanie Weaver, CDFW Wildlife Branch, (916) 502-1139
Peter Tira, CDFW Communications, (916) 215-3858

California Fish and Game Commission: No maximum size limit adopted for striped bass; CESA evaluation coming for one of state’s rarest plants

Wed, 15 Oct 2025 13:12:13 GMT

After years of discussion and consideration of public comment and scientific research, the California Fish and Game Commission (Commission) did not approve a proposed regulation amendment to set a maximum size limit for recreational striped bass fishing. This decision and regulatory action affecting California’s natural resources took place at the Commission’s October 8-9 meeting in Sacramento.

For recreational striped bass harvest, proposed regulatory amendments requested through an externally submitted petition would have kept the minimum size limit at 18-inches and set a maximum length limit at 30 inches for harvest of striped bass in anadromous waters. The petition’s stated goal was to protect larger, mature fish. The Commission voted 3-2 to not set a maximum size limit.

California Endangered Species Act (CESA) candidacy was granted for Gerry’s curly-leaved monardella and Pacific pocket mouse. Commissioners found sufficient scientific information to warrant possible CESA listings.

Gerry’s curly-leaved monardella is considered one of California’s rarest plants and the Pacific pocket mouse was once thought extinct. Each face threats such as habitat loss due to development. These species will now receive CESA protections while a status review is underway for potential CESA listing.

The Commission adopted regulations adding invasive non-native mussels, including golden mussel, pond mussel and axe-head mussel, and green crab to the list of live animals restricted from importation, transportation and possession.

As part of an emergency regulation, golden mussel was added to the list of restricted species in December 2024 after the discovery of golden mussel in California in October 2024. Golden mussel was first detected in the Port of Stockton and have since spread from the Sacramento-San Joaquin River Delta into other California waterways that receive water from the Delta.

Golden mussel, pond mussel, axe-head mussel and green crab pose threats to ecosystems, water infrastructure and economies. These invasive mussels can clog water pipelines, colonize inside boat engines and alter food webs affecting native species. Green crab outcompetes native species for food and habitat, disrupting marine ecosystems and threatening native fisheries; they also prey on farmed bivalves.

Inductees to the 2025 California Waterfowlers Hall of Fame were recognized at this Commission meeting. Fritz Reid, Mike Passaglia and Rex Carr were honored as individuals who have made significant contributions to enhance and conserve waterfowl and their habitats in California.

The closure of commercial bull kelp harvest in Sonoma and Mendocino Counties was extended through January 2029. Initially a three-year restriction on commercial bull kelp harvest from Sonoma County to the Oregon border was adopted in February 2022 in response to multi-year declines in bull kelp populations. Bull kelp has shown only limited reestablishment, warranting an extension.

Meeting Participation and Next Meeting

Commission President Erika Zavaleta, Vice President Samantha Murray and commissioners Jacque Hostler-Carmesin, Eric Sklar and Darius Anderson were in attendance for both days of the October Commission meeting.

The complete agenda for the meeting, along with supporting information, is available on the Commission website. Archived video of past Commission meetings is available online. The next meeting of the Commission is scheduled for December 10-11 at the California Natural Resources Building, second floor, 715 P St., Sacramento. Participants are encouraged to attend in person, with options available for Zoom or phone; for the agenda and more information visit the Commission website.

The Commission authorized staff to notify the public of potential regulation changes related to:

Recreational take of groundfish (PDF) A discussion hearing is scheduled for December 10-11 and an adoption hearing Febuary 11-12 on proposed amendments to regulations regarding recreational take of rockfish, cabezon, greenling and lingcod.

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Media Contacts: 
Krysten Kellum, CDFW Communications, (916) 825-7120
Katie Talbot, CDFW Communications, (916) 204-1381