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
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.
This week’s CaliforniaWaterBlog post is an excerpt (Box 1) from
a recent Delta Independent Science Board report on non-native
species and the California Delta. This excerpt summarizes
the experience of the Great Lakes, and how its physical and
ecological management has led to waves of profoundly disruptive
species invasions, resulting in a sequence of “novel”
ecosystems. This sequence of invasions seems likely to
continue to shape the Great Lakes. This history is a
wake-up and warning for policymakers and those working on
For over 50 years, researchers with the UC Davis Tahoe
Environmental Research Center (TERC) have been carefully
observing the waters of Lake Tahoe. This week, the annual
“State of the Lake” report was released. According to UC Davis
TERC director Geoffrey Schladow, 2021 data shows some major
changes that hadn’t been observed to this point. One of
the most notable is a drop in the Mysis shrimp population. This
non-native plankton species was introduced into the lake in the
Health and tribal officials are reporting that, due to
persistent drought and heat, they are finding unprecedented
levels of cyanotoxins in some areas of Clear Lake. For Lake
County residents with individual water systems that draw water
directly from the lake using a private intake, drinking water
may become unsafe when high levels of toxins are present, Lake
County Health Services reported. Of particular concern are
those with individual water systems who live around the Sulphur
Bank Mine, and along the shore of Clear Lake’s Lower and Oaks
Millions of highly skilled environmental engineers stand ready
to make our continent more resilient to climate change. They
restore wetlands that absorb carbon, store water, filter
pollution and clean and cool waters for salmon and trout. They
are recognized around the world for helping to reduce wildfire
risk. Scientists have valued their environmental services at
close to $179,000 per square mile annually. And they work for
free. Our ally in mitigating and adapting to climate change
across the West could be a paddle-tailed rodent: the North
American beaver. -Written by Chris Jordan, mathematical biology
and systems monitoring program manager at NOAA Fisheries’
Northwest Fisheries Science Center; and Emily Fairfax, an
assistant professor of environmental science and resource
management at Cal State Channel Islands.
The Biden-Harris administration today announced that the
Department of the Interior’s U.S. Fish and Wildlife Service has
awarded $3.4 million in funding from President Biden’s
Bipartisan Infrastructure Law for cooperative agreements with
the Washoe Tribe of California and Nevada and the Tahoe
Regional Planning Agency to combat the spread of aquatic
invasive species in Lake Tahoe. The funding represents a
historic effort dedicated to restoring the Lake Tahoe Basin
ecosystem and emphasizes the Administration’s commitment to
inclusive engagement with Tribes, partners and
The day’s first gillnet haul of nonnative fish on lower Lake
Powell was already alarming: three striped bass, three
gizzard shad and a channel catfish. Any one of them or their
offspring would be unwelcome intruders were they to slip
through the massive concrete dam’s hydropower tubes and
turbines to swim a few dozen miles downstream into the heart of
Grand Canyon. Above Glen Canyon Dam, state fisheries managers
in decades past would introduce alien species to support
recreational angling on the lake. But below the dam, the
fish could drift downstream to eat or outcompete Grand
Canyon’s threatened humpback chub population, swelling the
ranks of nonnatives that biologists are already battling.
Southern California is experiencing a drought of historic
proportions. In fact, some scientists are now referring to this
uber-drought as “aridification.” While droughts
are thought of as somewhat temporary, aridification signals a
whole new condition, one that Matthew Kirby, a
paleoclimatologist and professor at California State University
Fullerton, says, could mean living “under a permanent state
of water conservation.” Meanwhile, while the
summer months can mean mosquitos, a drought doesn’t necessarily
mean that their threat is diminished.
California may be winning its five-year, $13 million battle
with nutria — the 20-pound, orange-toothed swamp rodents that
biologists once feared would play hell with wetlands,
flood-control levees and the state’s water-delivery system. …
[Valerie Cook, who runs the Department of Fish and Wildlife’s
nutria eradication program] said her team is seeing nutria
numbers declining, and they’ve managed to keep them out of the
Sacramento-San Joaquin Delta, California’s most important
waterway. Scientists who deal with invasive pests were
first alarmed when nutria — a beagle-sized rodent native to the
wetlands of South America — were spotted in a private
duck-hunting marsh in the spring of 2017 near the farming
community of Gustine in Merced County.
A virulent and voracious species of invasive fish has
penetrated the ecologically delicate waterways of the lower
Colorado River, The Associated Press reported. The
presence of smallmouth bass below the critical
barrier of the Glen Canyon dam means an existential threat
to chub, an ancient native fish, according to the AP.
Wildlife biologists have long dreaded the day when the bass — a
sport fish introduced into the freshwater lakes of the West
— would make it through the dam to attack the
threatened chub, as we reported in June.
For National Park Service fisheries biologist Jeff Arnold, it
was a moment he’d been dreading. Bare-legged in sandals, he was
pulling in a net in a shallow backwater of the lower Colorado
River last week, when he spotted three young fish that didn’t
belong there. “Give me a call when you get this!” he messaged a
colleague, snapping photos. Minutes later, the park service
confirmed their worst fear: smallmouth bass had in fact been
found and were likely reproducing in the Colorado River below
Glen Canyon Dam. They may be a beloved sport fish, but
smallmouth bass feast on humpback chub, an ancient, threatened
fish that’s native to the river, and that biologists like
Arnold have been working hard to recover.
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.
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
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
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
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.