Invasive species, also known as exotics, are plants, animals,
insects, and aquatic species introduced into non-native habitats.
Without natural predators or threats, these introduced species
then multiply.
Often,invasive species travel to non-native areas by ship,
either in ballast water released into harbors or attached to the
sides of boats. From there, introduced species can then spread
and significantly alter ecosystems and the natural food chain as
they go. Another example of non-native species introduction
is the dumping of aquarium fish into waterways.
Invasive species also put water conveyance systems at risk. Water
pumps and other infrastructure can potentially shut down due to
large numbers of invasive species.
San Joaquin County is launching a task force to combat the
spread of golden mussels, an invasive species threatening the
local ecosystem and infrastructure, with the help of $20
million in state funding. Deep beneath the
Delta hides a threat to the ecosystem, as
golden mussels, discovered in the area for the first time last
year, are known for clogging pipes and harming native species.
… The new funding aims to establish infrastructure for
education, tagging, and inspections.
It’s been a year since golden mussels were first discovered in
California—and the state’s response has been swift and
strategic. In partnership with California State Parks and the
California Department of Fish and Wildlife, DWR is taking
decisive action to combat the spread of this invasive species
and safeguard California’s vital water infrastructure. Golden
mussels pose a serious threat to the State Water Project (SWP),
which delivers water to 27 million Californians and 750,000
acres of farmland. To protect this critical infrastructure, DWR
has launched a series of proactive measures aimed at minimizing
the mussels’ impact on our water conveyance system.
… Mute swans are kind of like “aquatic feral pigs,” CDFW
spokesperson Melanie Weaver told SFGATE over the phone
Wednesday. Despite their striking physical appearance, the
birds pose a serious threat to Northern California’s marine
ecosystem, and homeowners now have the authority to shoot them
if they’re on their property, regardless of whether they have a
license, Weaver said. That’s because mute swans
unapologetically consume up to 8 pounds of aquatic vegetation
per day, destroying crucial food and habitat for native
species.
… [N]utria are distinctly rat-like in appearance, with long
naked tails and vivid orange buck teeth. And they are big – up
to 20 pounds. They can consume 25% of their body weight in
vegetation daily and despoil up to 10 times that quantity.
They’re vectors for a variety of diseases and parasites, and
they burrow incessantly, posing a significant risk to
levees. … Agency [California Department
of Fish and Wildlife] staffers have trapped thousands over
the past seven years, but the doughty animals have maintained a
steady, seemingly inexorable expansion in range: north to the
Suisun Marsh and perhaps beyond, east up the
drainages of at least two rivers that feed into the San Joaquin
Valley.
It will soon be legal to hunt and kill mute swans anywhere in
California, after Governor Gavin Newsom signed state
legislation into law earlier this month. … Mute
swans are territorial and extremely aggressive, and do not mix
well with other waterfowl species native to the area. They do
not generally migrate and prefer to feed on primarily submerged
aquatic vegetation in wetlands, which are
limited across California, and are essential for many
wetland-dependent birds, native to the state. … Mute
swans were first found in the Suisun and Napa
marshes during the California Department of Fish and
Wildlife’s annual Waterfowl Breeding Population Survey in
2007.
Colorado is in its first year of responding to a zebra mussel
infestation in a big river, the Colorado River. State staff say
they have what they need to handle the high-priority needs —
they just need their funding to stay off the chopping
block. The fast-reproducing mussels, or their microscopic
stage called veligers, were first detected in Colorado in 2022.
Since then, the state’s Aquatic Nuisance Species team and its
partners have been working to monitor water, decontaminate
boats and educate the public to keep the mussels from
spreading. That effort logged a serious failure this summer
when state staff detected adult zebra mussels in the Colorado
River, where treatment options are limited.
… Nevada waterways are currently free of zebra and golden
mussels. But, Nevada officials and water managers are preparing
for what it could mean if the zebra or golden mussels find
their way into Lake Mead and other state water bodies and using
their experience with quagga mussels as a baseline.
Research shows that if quagga and zebra mussels are found in
the same area, quagga dominate zebra mussels, according to
Southern Nevada Water Authority (SNWA) Regional Water Quality
Manager Todd Tietjen. Research also shows that golden mussels
could outperform both of them, “which is why we are really
ramping up our detection efforts.”
Quick actions by boaters and paddlers this year helped prevent
the dangerous golden mussel and other aquatic invasive species
from entering the Lake Tahoe watershed, according to agencies
leading the Lake Tahoe Aquatic Invasive Species (AIS) program.
The Tahoe Regional Planning Agency (TRPA) and Tahoe Resource
Conservation District (Tahoe RCD), which manage the watercraft
inspection program, reported that inspectors performed more
than 4,700 decontaminations in 2025, a 60 percent increase
compared to the previous year.
… The [California Fish and Game] 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.
A new California law will allow hunters to kill nonnative
swans. Gov. Gavin Newsom signed the bill, Assembly Bill 764,
into law on Tuesday. The bill adds mute swans — the iconic
white swan brought to the United States to decorate parks and
estates — to the list of invasive birds that can be hunted with
few restrictions. … They’ve spread to lakes and
reservoirs across Northern California; however, [UC Davis
Museum of Wildlife and Fish Biology curator Andrew] Engilis
said they especially enjoy the open water in the
Sacramento-San Joaquin Delta, where
researchers have observed flocks as large as 400 birds.
… Every few years, wild pigs emerge from river habitat to
wreak havoc in the Fairmount Park area. … The pigs currently
roaming Riverside’s corridors descend from domestic swine that
escaped during catastrophic 1930s floods. … The Santa
Ana River corridor creates a green highway connecting
rural habitats to urban resources, with residential
neighborhoods serving as unintended waypoints between
wilderness areas. … The pigs have inhabited these river
bottoms longer than most human families, and they’ll probably
outlast current management strategies too.
The California Department of Water Resources is implementing
new safety measures after the discovery of invasive golden
mussels in Merced County. The California Department of Water
Resources (DWR), in collaboration with the California
Department of Fish and Wildlife (CDFW) and California State
Parks, is implementing new measures to protect the state’s
water infrastructure and curb the spread of invasive golden
mussels. This follows the recent discovery of the species at
San Luis Reservoir in Merced County, with confirmed findings in
Fresno and Kings Counties.
… [T]here’s only about 3,000 sea otters in California. The
playful predators’ voracious appetite for destructive species
like green crabs and purple urchins has transformed
Elkhorn Slough, the state’s second-largest
estuary, into an aquatic Serengeti and makes the
central coast’s carbon-sequestering kelp forests more resistant
to climate change. … The US government determined in
2022 that reintroducing sea otters on California’s North Coast
and Oregon would be a boon to biodiversity and climate
resilience. … But as the Trump administration moves to slash
funding for wildlife programs, a nonprofit co-founded by a
Silicon Valley entrepreneur is stepping in.
A new abatement project is underway in Madera County to help
reduce flood and wildfire risks while improving local water
supplies. The project targets Arundo donax, an invasive weed
that can grow up to four inches per day and reach 30 feet in
height. Highly flammable, the plant clogs waterways and can
cause floodwaters to overtop levees and other infrastructure,
posing a threat to public and private property. Last month,
crews completed a detailed, non-invasive drone mapping process
to identify key areas for removal.
After 35 years of working in organic pest control, serial
entrepreneur Pam Marrone is on a new mission to eradicate
invasive species using alternatives to terrible chemicals. In
particular, she’s on a quest for what she calls “the holy
grail” – an eco-friendly herbicide that will zap out non-native
weeds. “We have the team that can really execute it,” says
Marrone, whose 2-year-old startup, Invasive Species Corp.,
known as ISC, is already helping the state of California find a
sustainable way to deal with golden mussels,
which clog waterways and damage water treatment facilities.
“There’s nobody doing exactly what we’re doing with invasive
species.”
Five individuals have been caught illegally mining along
several California waterways, state officials
announced. According to a Sept. 26 news
release from the California Department of Fish and
Wildlife, the citations began in August of last year, when
authorities found someone operating a suction dredge — a
powerful tool that sucks materials out of underwater cracks and
crevices — on the Salmon River. … According to the CDFW,
this motorized equipment can harm fish and their native habitat
by releasing contaminants, causing erosion and potentially
creating more favorable conditions for the invasive signal
crayfish.
Officials at Pyramid Lake say starting Oct. 1, watercraft
inspections will become mandatory for any craft using the lake.
The new regulation was approved by the Pyramid Lake Paiute
Tribal Council to strengthen protections against the invasive
mussels already seen in the Lake Tahoe area. The council says
the adaptability of the Golden Mussels makes them a serious
threat to the lake and its surrounding bodies of water.
Starting Oct. 1, all motorized and/or trailered watercraft must
be inspected prior to launch at the lake.
Now that Colorado’s zebra mussel problem has been confirmed in
the Colorado River, the strategy for fighting
the invasion has started to shift. Colorado Parks and Wildlife
said it won’t try chemical treatments on the river as they’ve
done in the past with Highline Lake, one of the first spots CPW
found the mussels. It believes the risks that could bring to
native fish, along with the sheer scale of the waterway make
that impossible. Instead, the focus now is on containing the
spread and keeping mussels out of other lakes and reservoirs.
In a startling development for California’s water system, state
officials have confirmed the infestation of invasive golden
mussels (Limnoperna fortunei) at two major Southern California
lakes: Silverwood Lake in San Bernardino County and Pyramid
Lake in Los Angeles County. The rapid spread of this highly
destructive species from the Sacramento-San Joaquin Delta to
the southern reaches of the State Water Project marks a new
chapter in the state’s ongoing struggle to safeguard both water
infrastructure and delicate aquatic ecosystems. The golden
mussel is notorious worldwide for its ability to multiply
quickly, clog pipes and screens, destabilize local ecology, and
create costly headaches for urban, agricultural, and
recreational water systems.
… The invasive golden mussel has been confirmed at
Silverwood Lake in San Bernardino County and Pyramid Lake in
Los Angeles County, according to the Department of Water
Resources, the California Department of Fish and Wildlife and
California State Parks. The two lakes are now the southernmost
reservoirs in the State Water Project where the mussels have
been found. … The mollusk’s fast march across California
could spell trouble for the state’s vast network of canals,
reservoirs and pipelines, which shuttle water from the San
Joaquin Delta to other parts of the state.
A new aquatic invader, the golden mussel, has penetrated California’s ecologically fragile Sacramento-San Joaquin Delta, the West Coast’s largest tidal estuary and the hub of the state’s vast water export system. While state officials say they’re working to keep this latest invasive species in check, they concede it may be a nearly impossible task: The golden mussel is in the Golden State to stay – and it is likely to spread.
In the vast labyrinth of the West
Coast’s largest freshwater tidal estuary, one native fish species
has never been so rare. Once uncountably numerous, the Delta
smelt was placed on state and federal endangered species lists in
1993, stopped appearing in most annual sampling surveys in 2016,
and is now, for all practical purposes, extinct in the wild. At
least, it was.
This tour guided participants on a virtual journey deep into California’s most crucial water and ecological resource – the Sacramento-San Joaquin Delta. The 720,000-acre network of islands and canals support the state’s two major water systems – the State Water Project and the Central Valley Project. The Delta and the connecting San Francisco Bay form the largest freshwater tidal estuary of its kind on the West coast.
Nutria are large, beaver-like
rodents native to South America that have caused alarm in
California since their rediscovery along Central Valley rivers
and other waterways in 2017.
The growing leadership of women in water. The Colorado River’s persistent drought and efforts to sign off on a plan to avert worse shortfalls of water from the river. And in California’s Central Valley, promising solutions to vexing water resource challenges.
These were among the topics that Western Water news explored in 2018.
We’re already planning a full slate of stories for 2019. You can sign up here to be alerted when new stories are published. In the meantime, take a look at what we dove into in 2018:
Sixty percent of California’s developed water supply
originates high in the Sierra Nevada mountains. Our water
supply is largely dependent on the health of our Sierra forests,
which are suffering from ecosystem degradation, drought,
wildfires and widespread tree mortality.
We headed into the foothills and the mountains to examine
water issues that happen upstream but have dramatic impacts
downstream and throughout the state.
GEI (Tour Starting Point)
2868 Prospect Park Dr.
Rancho Cordova, CA 95670.
For more than 100 years, invasive
species have made the Sacramento-San Joaquin Delta their home,
disrupting the ecosystem and costing millions of dollars annually
in remediation.
The latest invader is the nutria, a large rodent native to South
America that causes concern because of its propensity to devour
every bit of vegetation in sight and destabilize levees by
burrowing into them. Wildlife officials are trapping the animal
and trying to learn the extent of its infestation.
Estuaries are places where fresh and
salt water mix, usually at the point where a river enters the
ocean. They form highly productive natural habitats due to a
combination of tides, waves, salinity, fresh water flow and
sediment.
A troublesome invasive species is
the quagga mussel, a tiny freshwater mollusk that attaches itself
to water utility infrastructure and reproduces at a rapid rate,
causing damage to pipes and pumps.
First found in the Great Lakes in 1988 (dumped with ballast water
from overseas ships), the quagga mussel along with the zebra
mussel are native to the rivers and lakes of eastern Europe and
western Asia, including the Black, Caspian and Azov Seas and the
Dneiper River drainage of Ukraine and Ponto-Caspian
Sea.
This 24×36 inch poster, suitable for framing, explains how
non-native invasive animals can alter the natural ecosystem,
leading to the demise of native animals. “Unwelcome Visitors”
features photos and information on four such species – including
the zerbra mussel – and explains the environmental and economic
threats posed by these species.
This 24×36 inch poster, suitable for framing, explains how
non-native invasive plants can alter the natural ecosystem,
leading to the demise of native plants and animals. “Space
Invaders” features photos and information on six non-native
plants that have caused widespread problems in the Bay-Delta
Estuary and elsewhere.
The 24-page Layperson’s Guide to the Delta explores the competing
uses and demands on California’s Sacramento-San Joaquin Delta.
Included in the guide are sections on the history of the Delta,
its role in the state’s water system, and its many complex issues
with sections on water quality, levees, salinity and agricultural
drainage, fish and wildlife, and water distribution.
