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.
The Eel River Pikeminnow Fishing Derby is back again, after
over 500 fish were caught in the 2024 derby. The derby is put
on by a collaboration of groups working to restore native
fishes in the Eel River. From now through August 31st, anyone
with a fishing license (or if under 16 years of age, no license
is necessary) can go and catch pikeminnow on the Eel for a
chance to win up to $500, with $2,500 in cash prizes! There is
no entry fee. Data from your catches can help managers aid in
the conservation of our native fishes. Pikeminnow were
introduced to the Eel River via Pillsbury Reservoir in the late
1970’s. Since then, they have spread to all the forks of the
Eel and are remarkably prolific. … The waters open to
fishing for the derby are: the South Fork Eel River downstream
of the Humboldt County line to the confluence with the
mainstem, the mainstem Eel from Dos Rios to the mouth of the
Van Duzen, and the Van Duzen from Grizzly Creek to the mouth of
the Van Duzen.
One of the state’s best investigators was on the hunt for
golden mussels — a dangerous new invader in
California’s waters, with a reputation for destruction.
Wearing a collar and a tongue-lolling grin, Allee, a Belgian
Malinois, sniffed along the glittering hull of a bass boat at
an inspection station in Butte County. … The dog was
searching for any hint of the thimble-sized mussels hidden in
the nooks and crannies of boats headed to Lake
Oroville, the state’s second-largest reservoir, or two
smaller reservoirs nearby. … State water managers made the
alarming discovery last October that golden mussels, which are
native to China and Southeast Asia, had invaded the
Sacramento-San Joaquin River Delta — the
core of California’s massive water delivery
systems. … Now the mussels are here to stay. They
cannot be eradicated. Water suppliers bracing for the onslaught
have instead turned their efforts to shoring up pipes, pumps
and treatment plants against the infestation.
The Colorado River is now officially “positive” for invasive
zebra mussels in the latest failure of containment for the
voracious species, after three new samples came up with larvae
July 3, from between Glenwood Springs and Silt. The main stem
Colorado River discoveries piled on top of a confirmed “large
number” of adult zebra mussels in a private body of water in
western Eagle County, and two more positive larvae tests, at
Highline Lake and Mack Mesa Lake, both near the Utah border,
Colorado Parks and Wildlife officials said Wednesday. Sampling
was redoubled throughout June after tests found a single zebra
mussel larvae, or veliger, in the Colorado River from a June 9
collection. It’s the second year in a row veligers are
being discovered in the West’s key river channel through
Colorado, and now CPW officials are also dealing with a
full-blown adult zebra mussel invasion in the privately owned
Eagle County water.
Fishing fans, here’s your chance to cast a line for a good
cause—and maybe reel in some prize money while you’re at it.
The Eel River Pikeminnow Fishing Derby is now underway, running
from July 1 through August 31, and organizers are inviting
anglers of all ages to join in. The idea? Catch as many
non-native Sacramento pikeminnow as you can from the Eel River
system and submit your catch for a chance to win part of $2,500
in cash prizes. … So why target Sacramento pikeminnow?
Although they’re native to parts of California, pikeminnow were
introduced into the Eel River in the 1970s, where they now pose
a serious threat to native fish. As voracious predators,
pikeminnow eat native salmonids and lamprey—both already under
pressure from habitat loss, drought, and climate change.
Reducing pikeminnow numbers can help protect these struggling
native populations.
The invasive two-inch wide golden mussel showed up near the
Port of Stockton last fall. Since then, it’s spread south,
extending to other waterways in the Delta and some in the San
Joaquin Valley. Now, eyes are looking north to Lake
Oroville, where the mussels could pose a large threat if
they’re introduced. The reservoir is the second largest in
California. … The mussels also pose a significant
environmental threat. Eric See is with the Department of Water
Resources. He said Lake Oroville feeds water into the Feather
River Fish Hatchery through small diameter piping. It raises
steelhead trout and chinook salmon. Chinook populations are
threatened, and the state is currently trying to bring them
back. If that pipe gets blocked, it cuts off water to the fish.
… The mussels could also create large algae blooms that can
kill fish and filter water, increasing aquatic weed growth.
That makes it harder for fish in the water to navigate and find
food.
An invasion of smallmouth bass from the Great Lakes region is
spreading to new areas of the Colorado River in Arizona. The
bass have already thwarted efforts to save threatened native
fish in the upper river basin, and wildlife officials are
fighting to keep the same from happening below Lake Powell,
even if it requires cranes, excavators and maybe one day, a
giant metal curtain. Federal officials say they took a major
step in fighting the bass invasion below the Glen Canyon Dam in
June. The National Park Service and Bureau of Reclamation have
cleared out a warm backwater in the river where bass and other
invasive species used to spawn, eliminating a critical resource
for the predatory fish that could wipe out one of the last
holdouts for some of the Colorado River’s threatened and
endangered fish. Every bass that spawned in the slough
became a threat to native fish, experts say. Smallmouth bass
eat native fish eggs and young.
The first discovery of golden mussels in North
America at Rough and Ready Island near Stockton in San Joaquin
County has water managers throughout California on the alert,
including the Yuba Water Agency, which manages New Bullards Bar
Reservoir. On Tuesday, the Yuba Water Agency announced that it
will launch a new watercraft screening pilot program later this
summer at New Bullards Bar Reservoir in Yuba County. The pilot
program aims to prevent the spread of the golden mussel, a
highly invasive species found in the Sacramento-San
Joaquin Delta last fall that could pose a
significant ecological and economic threat to the Yuba River
watershed. … Thus far, all the sightings of golden
mussel have been concentrated in the delta, although five
additional sightings have been reported in the San Joaquin
Valley.
Before enjoying Ruth Lake this summer, be sure to clean, drain
and dry all gear, boats and trailers to prevent the spread of
the invasive golden mussel. The golden mussel, native to East
and Southeast Asia, was first documented in California in 2024.
Like quagga and zebra mussels, the golden mussel is capable of
rapidly spreading, wreaking ecological health and threatening
water infrastructure and water quality. Thomas Jabusch of the
California Department of Fish and Wildlife and Michiko Mares of
the Humboldt Bay Municipal Water District join the program to
golden mussels, their threat, and what you can do to stop the
spread of this invasive species.
Golden mussels are an invasive aquatic species that disrupt
ecosystems, filter away nutrients and damage shorelines
– and they were recently spotted on a boat trying to enter
Lake Tahoe. … This season, boating in California’s
Folsom Lake State Recreation Area requires a mandatory 30-day
quarantine or decontamination, while other water bodies like
Shasta Lake do not require any pre-launch inspection. No matter
the protocol, the spread of the golden mussel has raised alarm
among scientists and advocates, and its spotting in the Tahoe
basin is no small scare. … In the past, some
marinas shut down completely after the discovery of a new
invasive species – this happened in Lake Mead after the 2007
introduction of zebra mussels. Because Tahoe is so intertwined
with outdoor recreation, though, enhanced enforcements need to
be thoughtfully crafted.
… In new research published in the journal Biological
Conservation, (UC Davis PhD candidate Sidney) Woodruff and her
colleagues propose a possible — though intensive —
countermeasure: a near-total eradication of the bullfrog from
habitats that it has invaded. The result was the striking
recovery of the Northwestern pond turtle, California’s only
native freshwater pond turtle species, at a couple of remote
bodies of water within Yosemite National Park.
… Woodruff and her colleagues conducted a combination of
night surveys to remove the adults and day surveys to go after
bullfrog egg masses. Across two sites, she estimates they
removed some 16,000 bullfrogs, amounting to a near-complete
eradication. And after several years of removal, “we came
across our first couple of small pond turtle hatchlings and
juveniles swimming out in the environment,” says Woodruff.
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 are the meeting point between riverine environments
and the sea, with a combination of tides, waves, salinity, fresh
water flow and sediment. The constant churning means there are
elevated levels of nutrients, making estuaries highly productive
natural habitats.
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.
