Fish Slough - Bureau of Land Management
Area of Critical Environmental Concern
U.S. Department of the Interior
Bureau of Land Management
A Cooperative Management Program
Fish Slough is a lush oasis in an arid landscape known
as the Volcanic Tableland. The wetland and part of the
Volcanic Tableland totaling 36,000 acres is designated
as an Area of Critical Environmental Concern (ACEC)
to recognize, maintain, and enhance its unique resource
You will discover the ACEC is a special place. The
marsh creates a rich environment supporting diverse
plant and animal life, including several unique and
sensitive species. Nestled between the towering White
Mountains to the east and Sierra Nevada to the west,
the unusual geological features that give rise to the
springs make a colorful landscape of cliffs and terraces
with warm pastel hues that are especially striking in
the early morning and evening hours. Prehistoric and
historic peoples were also drawn to this habitat for
the special resource values we recognize today. Several
agencies manage the ACEC under a Cooperative Management
Plan, with the help of volunteers from the Eastern Sierra
How to Get There
Fish Slough ACEC is easy to find, in east-central California
at the north end of the Owens Valley, 5 miles north
of Bishop. You can drive to the ACEC via graded dirt
roads from U.S. Highway 395 and U.S. Highway 6. No visitor
services are provided in this isolated desert environment
so travelers are advised to be prepared.
A Land Formed by Cataclysm
Violent geologic events are the natural forces underlying
Fish Slough's subtle beauty. Glowing hot rhyolite ash
flowed like a scorching avalanche out of the Long Valley
Caldera 760,000 years ago, destroying every living thing
in its path and blanketing the landscape several hundred
feet deep for miles around. This pyroclastic flow then
fused to create the porous white, pink and tan rock
called Bishop tuff that makes up the Volcanic
Later, faulting action warped and cracked the gentle
slope of the Tableland, lifting some parts and dropping
others. The smooth surface broke into blocks that that
eroded into jagged or oddly curving forms. The small
round bumps that dot some parts of the Tableland are
the result of fumaroles of hot water and steam that
vented from the cooling ash flow and hardened the tuff
so that it resisted erosion.
Pick up a piece of Bishop tuff and notice how light
it is. Air pockets in the hot ash flow became small
holes that allow water to pass through quickly. Water,
wind and earthquakes continue to change the landscape
you see today. One of the most active fault scarps runs
along the east side of Fish Slough. Rising abruptly
from the edge of the Tableland, the East Side Bluff
is more than 5 miles long and 300 feet high!
Water in the Desert
The Volcanic Tableland lies at the meeting place of
the Great Basin Desert to the north and the Mojave Desert
to the south. The geologic forces that created the Tableland
also created an oasis in these arid lands. The faulting
action that lifted the East Side Bluff threw a huge
block of land at its base down to the level of the water
table, so that a rich wetland was formed.
Look closely into the bottoms of the pools at the north
end of Fish Slough. The upwelling bubbles you may see
are springs that feed the pools and replenish the marsh.
Three perennial, free-flowing freshwater spring systems
merge their waters to flow south toward the Owens River.
The springs and their outflow are surrounded by wet
marshlands. These, in turn, are bordered by seasonally
wet alkali meadows, frosted with
a white crust of minerals left by evaporating water.
Because of the water in Fish Slough, there is a greater
abundance of life here than in the surrounding desert.
What differences in life can you see between Fish Slough
and the Volcanic Tableland?
Lives in the Balance
Water is the key to the varied life found in Fish Slough.
Outside the marsh, Great Basin and Mojave Desert plants
survive extreme heat and cold with very little water.
These hardy plants include shadscale, Parry saltbrush,
four-wing saltbush, spiny hopsage, bud sage, Indian
ricegrass, and desert trumpet. Seeds of annual plants
lie dormant until a wet springtime when the Volcanic
Tableland suddenly blooms with brilliant colors, including
vast sweeps of the bright yellow Venus blazing-star.
This high desert habitat is home for many animals.
You might see some of the more common ones: coyotes,
black-tailed jackrabbits, white-tailed antelope squirrels,
gopher snakes, rattlesnakes, desert spiny lizards, sage
sparrows, rock wrens and mourning doves. The boulders
and cliffs of the fault scarps offer excellent hunting,
perching and nesting sites for golden eagles and prairie
Notice the change in the vegetation and animal life
as you look from the high desert over to the marshland.
The seasonally saturated alkali meadows support a rare
community of plants adapted to the high alkalinity and
varying water levels. At water's edge the vegetation
changes to a type that is even more water-dependent.
Bulrushes, cattails, sedges, willows and cottonwoods
are a few of the plants that thrive here.
You can find wildlife here that depend on the marsh
for at least part of their life cycle. Green-Winged
and Cinnamon Teals, Mallards, Ruddy Ducks, Pintails
and Gadwalls frequent the marsh, especially during spring
and fall. Great Blue Herons, American Bitterns, Northern
Harriers, Common Yellowthroats and Marsh Wrens also
use the wetlands, and this oasis in the desert attracts
rare migrating birds far from their usual home. You
may also see raccoons or striped skunks wading in the
shallows, or deer coming to drink.
The terms "endangered" and "threatened"
are applied to plants and animals that are protected
because of their uniqueness, special habitat needs,
and potential threat of extinction. One plant, the Fish
Slough milk vetch (Astragalus lentiginosus var.
piscinensis), is federally listed as a threatened
species. You cannot find this low-growing perennial
forb anywhere in the world except the alkali meadows
of Fish Slough. It was discovered in 1974 by Mary DeDecker,
a local botanist. Nearby you may find the white flowers
of the alkali mariposa lily (Calochortus excavatus),
a BLM Sensitive Species that also has very limited distribution.
Five other rare plant species depending on the life
giving waters of Fish Slough are alkali cordgrass
(Spartina gracilis), hot spring fimbristylis
(Fimbristylis thermalis), Great Basin centaurium
(Centaurium exaltatum), King's ivesia
(Ivesia kingii var. kingii), and silverleaf
milk vetch (Astragalus argophyllus var. argophyllus).
You may be able to find and photograph these in the
marsh and alkali flats.
Move closer to the water's edge. Spend a few moments
sitting quietly and gazing into a clear pool. What kinds
of life forms can evolve and thrive in an isolated desert
The endangered Owens pupfish is a small fish
observed in vast numbers throughout the Owens Valley
in 1859 by U.S. Army Captain J. W. Davidson, and still
abundant in 1916 in the north end of the valley. However,
Owens pupfish numbers and habitat were dwindling. Water
diversions and wetland drainage were responsible, along
with the introduction of predatory fish. By 1948 the
species was believed extinct - but in 1964 a small population
was rediscovered in Fish Slough.
Owens pupfish feed on insect larvae and other small
aquatic creatures and can survive in warm, salty water
with low oxygen levels. The males will fight aggressively
to defend the small territories where they display their
blue and silver breeding colors to attract a mate.
The Owens speckled dace is a subspecies of speckled
dace now found in very few sites within the Owens River
drainage. It was thought to be gone from Fish Slough
but was rediscovered here in 2002. Biologists hope to
reintroduce the once-abundant Owens sucker and
Owens tui chub to parts of the slough that are
safe from non-native fish. Owens tui chub became endangered
mainly because of interbreeding with other chubs that
were imported as bait. Non-native species such as large-mouth
bass and crayfish prey on the smaller natives, while
mosquitofish compete with them. Non-native animals can
disrupt the fragile natural balance of this complex
Of the many small aquatic invertebrates, the Fish
Slough springsnail is unique. This diminutive snail,
barely larger than the head of a pin, is found in specific
freshwater locations in the Fish Slough wetland - and
nowhere else in the world.
Fish Slough's abundant resources naturally attracted
Native Americans to the area. Food sources included
various wetland and desert scrub plant resources, waterfowl,
deer, pronghorn, rabbits, freshwater mollusks, and the
native desert fishes. Fish were caught by using plant
derived poisons and fishing nets, and by dragging baskets
through the water. Indian ricegrass, a major food source,
was harvested and carried in durable baskets woven from
willow. Duck eggs could be gathered and carried with
temporary baskets woven on the spot from bulrushes.
Mysterious Rock Art
You can find many prehistoric rock art sites in the
Fish Slough ACEC. These carvings, called petroglyphs,
were made by Native Americans prior to white settlement.
Notice the unusual geometric symbols and designs of
the petroglyphs. Their meaning has many interpretations,
often associated with shamanic or hunting magic. One
theory speculates a relationship may exist between these
carvings and hunting rituals since game trails are found
near many petroglyphs sites. However, this is a mystery
that may never be solved.
Over the centuries many Native American cultures have
used Fish Slough; most recently, the Owens Valley Paiute
Indians. Besides petroglyphs, other prehistoric sites
in the ACEC include temporary camps, semipermanent village
sites, and lithic scatters - the scraps left from stone
New Settlers in the Deepest Valley
During the 1860s ranchers and miners began to occupy
the present day areas of Bishop and Laws. These and
other new settlers homesteaded land in America's deepest
valley along creeks, rivers and springs. Part of the
Fish Slough wetland was pioneered by Phillip Keough
in 1890, who set up a stage stop near the northwest
In the last quarter of the 19th century the Fish Slough
Road became a main wagon route connecting Bishop and
Laws to the prosperous mining camps of Benton Hot Springs,
Bodie and Aurora. Freight and supplies were transported
on this route, which also served as a cattle driveway.
Dust-covered settlers routinely traveled this rutted
and sandy road to Bishop from as far north as Reno and
In the 1920s and 1930s the City of Los Angeles bought
riparian lands in the Owens Valley, including Fish Slough,
in order to acquire water rights and supply water to
a growing city. As a secondary result, intensive agricultural
uses and private land development were precluded here.
After the remnant population of Owens pupfish was discovered
in the 1960s, the City of Los Angeles Department of
Water and Power and the California Department of Fish
and Game established the Fish Slough Native Fish Sanctuary.
Since then the wetland has become increasingly recognized
for its unique qualities and ecological significance.
Looking to the Future
Since developing a Cooperative Management Plan in 1985,
five agencies have taken steps to preserve the area's
ecosystem by striving to study, protect and enhance
the ACEC's water quality and quantity, plants, animals,
and scenic values. The plan encourages public access
and recreation use that is consistent with maintaining
the natural integrity of the ACEC.
Public awareness and support of the ACEC's special
values is essential to successfully protect them. Your
knowledge and appreciation of Fish Slough's resources
can contribute to the ACEC's long-term ecological health.
Your help is needed to protect the ACEC's resources!
- Animals, plants, physical features, and historic
and prehistoric sites and artifacts are protected
by law and may not be removed, disturbed or damaged.
- Except where posted otherwise, fish only for bass,
carp and catfish according to California Department
of Fish and Game regulations.
- Although it may appear harmless, introduction of
non-native plants or animals is prohibited - they
can seriously alter and damage this fragile environment.
- Please pack out garbage you bring into the ACEC.
Packing out litter left by others also helps.
- Since physical scars from cross country vehicle
use remain visible for many years, all vehicles are
required to stay on designated roads.
- Signs are a tool to protect the area from unintentional
visitor abuse. Please respect signs restricting swimming,
fishing, and driving in certain areas at certain times.
- Help us improve this area by volunteering to assist
with conservation projects. Contact any of the cooperating
management agencies to learn more.
Cooperating Management Agencies
The Bureau of Land Management is responsible for the
balanced management of public lands and resources to
best serve the needs of the American people.
USDI Bureau of Land Management
351 Pacu Lane
Bishop, CA 93514
The Department of Fish and Game manages California's
diverse fish, wildlife and plant resources for their
ecological values and for use and enjoyment by the public.
California Department of Fish and Game
407 West Line Street
Bishop, CA 93514
The U.S. Fish and Wildlife Service implements the Endangered
Species Act and other federal laws governing wildlife
USDA Fish and Wildlife Service
2800 Cottage Way, Room E-1803
Sacramento, CA 95825-1846
The University of California, through its Natural Reserve
System, conducts management related research and advises
on natural areas management.
Valentine Eastern Sierra Reserve
University of CA, Santa Barbara
HCR 79, Box 198
Mammoth Lakes, CA 93546
The Department of Water and Power administers land
for watershed values, electric power generation, and
other multiple uses for the City of Los Angeles.
Los Angeles Department of Water and Power
300 Mandich Street
Bishop, CA 93514