Elkhorn Slough is a tidal

slough Slough () is a town and unparished area in the unitary authority of the same name in Berkshire, England, bordering west London. It lies in the Thames Valley, west of central London and north-east of Reading, at the intersection of the M4, ...

and

estuary An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environm ...

Monterey Bay Monterey Bay is a bay of the Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica ...

Monterey County, California Monterey County ( ), officially the County of Monterey, is a county located on the Pacific coast in the U.S. state of California. As of the 2020 census, its population was 439,035. The county's largest city and county seat is Salinas. Monte ...

. It is California's second largest estuary and the United States' first estuarine sanctuary. The community of Moss Landing and the

Moss Landing Power Plant The Moss Landing Power Plant is a natural gas powered electricity generation plant located in Moss Landing, California, United States, at the midpoint of Monterey Bay. Its large stacks are landmarks, visible throughout the Monterey Bay Area. T ...

are located at the mouth of the slough on the bay. Elkhorn Slough harbors the largest tract of tidal

salt marsh A salt marsh or saltmarsh, also known as a coastal salt marsh or a tidal marsh, is a coastal ecosystem in the upper coastal intertidal zone between land and open saltwater or brackish water that is regularly flooded by the tides. It is domin ...

in California outside the

San Francisco Bay San Francisco Bay is a large tidal estuary in the United States, U.S. state of California, and gives its name to the San Francisco Bay Area. It is dominated by the big cities of San Francisco, San Jose, California, San Jose, and Oakland, Ca ...

and provides much-needed habitat for hundreds of species of plants and animals, including more than 340 species of birds. It has been designated as a protected

Ramsar site A Ramsar site is a wetland site designated to be of international importance under the Ramsar Convention,8 ha (O) *** Permanent 8 ha (P) *** Seasonal Intermittent < 8 ha(Ts) **

History

The name of the slough derives from the native

tule elk The tule elk (''Cervus canadensis nannodes'') is a subspecies of elk found only in California, ranging from the grasslands and marshlands of the Central Valley to the grassy hills on the coast. The subspecies name derives from the tule (), a ...

''Cervus canadensis nannodes'', now extirpated from the region. Elkhorn Slough occupies the western reaches of Elkhorn Valley, a relic river valley eroded by drainage pouring out of the Santa Clara Valley and/or Great Valley of California (before the

Golden Gate The Golden Gate is a strait on the west coast of North America that connects San Francisco Bay to the Pacific Ocean. It is defined by the headlands of the San Francisco Peninsula and the Marin Peninsula, and, since 1937, has been spanned by ...

opened) into Monterey Bay during the early Pleistocene. In the mid-1850s A.D. Elkhorn Slough was a minor tributary to the much larger Pajaro-Salinas River system which shared a common entrance to the Pacific Ocean north of Moss Landing. In 1909 winter storms modified the course of the Salinas River to its present location south of Moss Landing, while Elkhorn Slough persisted as a tributary to the Old Salinas River channel. Construction of jetties at the Moss Landing Harbor in 1946 provided a direct link between the Pacific Ocean and Elkhorn Slough. At this time, salt marshes began to retreat from the axis of Elkhorn Slough as it evolved into its present form as a relatively stable estuarine embayment.

Watershed

Carneros Creek is the primary source of freshwater flowing into Elkhorn Slough. McClusky Slough to the north and Moro Cojo Slough to the south also provide freshwater inputs.

Conservation ownership

More than of the watershed's are protected under a

mosaic A mosaic is a pattern or image made of small regular or irregular pieces of colored stone, glass or ceramic, held in place by plaster/mortar, and covering a surface. Mosaics are often used as floor and wall decoration, and were particularly pop ...

of private and public ownership.

Foundations

The nonprofit

Elkhorn Slough Foundation Elkhorn or Elk Horn may refer to: Places Antarctica * Elkhorn Ridge, a ridge of the Convoy Range in Victoria Land Canada * Elkhorn, Manitoba, an unincorporated community * Elkhorn Mountain, a mountain in British Columbia United States Cities an ...

is the single largest land owner in the watershed, with nearly . The nonprofit

Nature Conservancy The Nature Conservancy (TNC) is a global environmental organization headquartered in Arlington, Virginia. it works via affiliates or branches in 79 countries and territories, as well as across every state in the US. Founded in 1951, The Natu ...

was the first to buy Elkhorn Slough property with the goal to protect the area's habitat and wildlife. The Nature Conservancy started with only 60 acres in 1971 and through gifts and purchases of disjointed parcels, gained over by September 2012, when it transferred to the Elkhorn Slough Foundation. The Foundation already managed conservation on these parcels. Sea-otter-morro-bay 13

Elkhorn Slough State Marine Reserve

The Elkhorn Slough State Marine Reserve (SMR) covers . The SMR protects all marine life within its boundaries. It is managed by the California Department of Fish & Wildlife (CA-DFW) in cooperation with the

National Oceanic and Atmospheric Administration The National Oceanic and Atmospheric Administration (abbreviated as NOAA ) is an United States scientific and regulatory agency within the United States Department of Commerce that forecasts weather, monitors oceanic and atmospheric conditi ...

. Fishing and take of all living marine resources is prohibited. It includes the waters below mean high tide within Elkhorn Slough lying: * east of longitude 121° 46.40’ W. and * south of latitude 36° 50.50’ N.

Elkhorn Slough State Marine Conservation Area

The Elkhorn Slough State Marine Conservation Area (SMCA) covers . It includes the waters below mean high tide within Elkhorn Slough: * east of the Highway 1 Bridge and * west of longitude 121° 46.40’ W. The SMR and the SMCA were both established in September 2007 by the

California Department of Fish and Wildlife The California Department of Fish and Wildlife (CDFW), formerly known as the California Department of Fish and Game (CDFG), is a state agency under the California Natural Resources Agency. The Department of Fish and Wildlife manages and protec ...

(CA−DFW). It was one of 29 marine protected areas adopted during the first phase of the

Marine Life Protection Act The Marine Life Protection Act (MLPA) was passed in 1999 and is part of the California Fish and Game Code. The MLPA requires California to reevaluate all existing marine protected areas (MPAs) and potentially design new MPAs that together form a s ...

Initiative, a collaborative public process to create a statewide network of marine protected areas along the California coastline.California Department of Fish and Wildlife,
Central Coast Marine Protected Areas
" . retrieved December 23, 2008.

Elkhorn Slough National Estuarine Research Reserve

The

Elkhorn Slough National Estuarine Research Reserve The Elkhorn Slough National Estuarine Research Reserve is a nature reserve that is located at 1700 Elkhorn Road in Watsonville, California. The reserve encompasses the central shore of Monterey Bay and is approximately south of San Francisco, ...

is one of 28 National Estuarine Research Reserves established nationwide as field laboratories for scientific research and estuarine education.

Local government

Additional land protected by the Moss Landing Harbor District and the Monterey County Parks Department

Adjacent areas

The Moss Landing Wildlife Area protects the land north and west of the Slough. The

Moro Cojo Slough State Marine Reserve Moro Cojo Estuary State Marine Reserve (SMR) is a marine protected area established to protect the wildlife and habitats in Moro Cojo Slough. Moro Cojo Slough is located inland from Monterey Bay on the central coast of California, directly south ...

just south of Elkhorn protects a similar wetland area.

Habitat and wildlife

Elkhorn Slough, one of the largest

estuaries An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environme ...

in California, provides essential habitat for over 700 species, including aquatic mammals, birds, fish,

invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...

alga Algae ( , ; : alga ) are any of a large and diverse group of photosynthetic, eukaryotic organisms. The name is an informal term for a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from u ...

e and plants. The slough area is home to California's greatest concentration of

sea otter The sea otter (''Enhydra lutris'') is a marine mammal native to the coasts of the northern and eastern North Pacific Ocean. Adult sea otters typically weigh between , making them the heaviest members of the weasel family, but among the sma ...

s, as well as populations of

endangered An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and inv ...

Santa Cruz long-toed salamander and the

threatened Threatened species are any species (including animals, plants and fungi) which are vulnerable to endangerment in the near future. Species that are threatened are sometimes characterised by the population dynamics measure of ''critical depensa ...

California red-legged frog The California red-legged frog (''Rana draytonii'') is a species of frog found in California (USA) and northern Baja California (Mexico). It was formerly considered a subspecies of the northern red-legged frog (''Rana aurora''). The frog is an IU ...

. The population of sea otter living in Elkhorn Slough reflect that the species is well-adapted for estuarine habitat, and may be a model for the historical sea otter populations now extinct in

. Elkhorn Slough hosts year-round residents tightly associated with estuaries, such as pickleweed,

eelgrass Eelgrass is a common name for several plants and may refer to: * ''Zostera'', marine eelgrass * ''Vallisneria ''Vallisneria'' (named in honor of Antonio Vallisneri) is a genus of freshwater aquatic plant, commonly called eelgrass, tape grass or ...

oyster Oyster is the common name for a number of different families of salt-water bivalve molluscs that live in marine or brackish habitats. In some species, the valves are highly calcified, and many are somewhat irregular in shape. Many, but not a ...

gaper clam ''Tresus'' is a genus of saltwater clams, marine bivalve mollusks in the family Mactridae. Many of them are known under the common name the horse clam or as species of gaper clam. They are similar to geoducks. Species Species within the genus ...

s, and

longjaw mudsucker The longjaw mudsucker ''Gillichthys mirabilis'' is a goby ( Gobiidae) of the Pacific Ocean coast of California and Baja California, noted for its extremely large mouth and ability to survive out of water for short periods. As the common name su ...

s, as well as important seasonal visitors such as migratory shorebirds, sea otters, and sharks and rays. Habitat types include mudflats, tidal creeks and channels. Other vegetative species include such wildflowers as yellow mariposa lily, ''

Calochortus luteus ''Calochortus luteus'', the yellow mariposa lily, is a mariposa lily endemic to California. Description The primarily bright deep yellow flower is 3–5 cm across and perianth bulb-shaped, lined red-brown inside, often also with central re ...

''.

Restoration

Conservation groups have worked to remedy indirect harm from human activity in the region in addition to preventing direct damage to the ecosystem by harvest of resources and conversion of land.

Parson's sill

A steel weir was built in 2010 at the mouth of the Parson's Slough, a fork of the Elkhorn. The weir or "sill" is intended to reduce the excess erosion of the marsh caused by the dredging of the Moss Landing Harbor and the redirection of the Salinas River. Primary funding came from a $3.9 million federal stimulus grant. The project was a collaboration among the

California Coastal Conservancy The California State Coastal Conservancy (CSCC, SCC) is a non-regulatory state agency in California established in 1976 to enhance coastal resources and public access to the coast. The CSCC is a department of the California Natural Resources Agen ...

David and Lucile Packard Foundation The David and Lucile Packard Foundation is a private foundation that provides grants to not-for-profit organizations. It was created in 1964 by David Packard (co-founder of HP) and his wife Lucile Salter Packard. Following David Packard's death ...

, DFG,

Ducks Unlimited Ducks Unlimited (DU) is an American nonprofit organization 501(c) dedicated to the conservation of wetlands and associated upland habitats for waterfowl, other wildlife, and people. It has had a membership of around 700,000 since January 2013. ...

, Elkhorn Slough Foundation, NOAA, URS Corporation, and the

U.S. Environmental Protection Agency The Environmental Protection Agency (EPA) is an independent executive agency of the United States federal government tasked with environmental protection matters. President Richard Nixon proposed the establishment of EPA on July 9, 1970; it be ...

Hester marsh restoration

The Tidal Marsh Restoration Project has been progressing since 2010. Most other Elkhorn salt marshes are projected to be drowned within 50 years. An elevated marsh plane is being created at Hester Marsh to establish a functional salt marsh ecosystem.

Recreation

Along with hiking and bird watching, kayaking and stand-up paddle boarding are popular activities on the slough. Watching

s, sea lions, seals,

brown pelican The brown pelican (''Pelecanus occidentalis'') is a bird of the pelican family, Pelecanidae, one of three species found in the Americas and one of two that feed by diving into water. It is found on the Atlantic Coast from New Jersey to the mo ...

American avocet The American avocet (''Recurvirostra americana'') is a large wader in the avocet and stilt family, Recurvirostridae, that is found in North America. It spends much of its time foraging in shallow water or on mud flats, often sweeping its bill f ...

cormorant Phalacrocoracidae is a family of approximately 40 species of aquatic birds commonly known as cormorants and shags. Several different classifications of the family have been proposed, but in 2021 the IOC adopted a consensus taxonomy of seven ge ...

egrets Egrets ( ) are herons, generally long-legged wading birds, that have white or buff plumage, developing fine plumes (usually milky white) during the breeding season. Egrets are not a biologically distinct group from herons and have the same build ...

tern Terns are seabirds in the family Laridae that have a worldwide distribution and are normally found near the sea, rivers, or wetlands. Terns are treated as a subgroup of the family Laridae which includes gulls and skimmers and consists o ...

s and a host of other wildlife from the water is an experience that provides a unique perspective of how the slough is used by the native inhabitants. People are encouraged to keep at least 100 feet of distance between them and wildlife on the slough. The Elkhorn Slough National Estuarine Research Reserve and Elkhorn Slough Foundation provide on-site management, education, and stewardship and offer public access via of trails, as well as a Visitor Center and volunteer opportunities. The nearby Moss Landing Wildlife Area protects of salt ponds and salt marsh. Limited recreation is permitted within the Wildlife Area. Harvest of finfish (by hook-and-line only) and clams are allowed within the conservation area only. Clams may only be taken on the north shore of the slough in the area adjacent to the Moss Landing State Wildlife Area. The

California Office of Environmental Health Hazard Assessment The Office of Environmental Health Hazard Assessment, commonly referred to as OEHHA (pronounced oh-EEE-ha), is a specialized department within the cabinet-level California Environmental Protection Agency ( CalEPA) with responsibility for evaluatin ...

has issued a saf
advisory
for any fish caught in Elkhorn Slough due to elevated levels of mercury and PCBs. In addition, there is a notice of "DO NOT EAT" for leopard sharks and bat rays for women 18–45 years old and children 1–17 years old. California’s marine protected areas encourage recreational and educational uses of the ocean. Activities such as kayaking, diving, snorkeling, and swimming are allowed unless otherwise restricted. The Moss Landing Harbor District has jurisdiction over the navigable waterways of Elkhorn Slough and owns Kirby Park at the upper reaches of Elkhorn Slough. Kirby park has a small boat launch and provides parking for a small trail on Nature Conservancy property at the north side. The trail here is fully handicapped-accessible and allows a walk and a wheelchair near the water's edge.

Scientific monitoring

As specified by the Marine Life Protection Act, select marine protected areas along California’s central coast are being monitored by scientists to track their effectiveness and learn more about ocean health. Similar studies in marine protected areas located off of the

Santa Barbara Channel Islands The Channel Islands () are an eight-island archipelago located within the Southern California Bight in the Pacific Ocean, off the coast of California. The four Northern Channel Islands are part of the Transverse Ranges geologic province, and ...

have already detected gradual improvements in fish size and number.Castell, Jenn, et al.
How do patterns of abundance and size structure differ between fished and unfished waters in the Channel Islands? Results from SCUBA surveys
". Partnership for Interdisciplinary Studies of Coastal Oceans (PISCO) at University of California, Santa Barbara and University of California, Santa Cruz; Channel Islands National Park. Retrieved December 18, 2008.

References

External links

The official website of the Elkhorn Slough Foundation and Elkhorn Slough National Estuarine Research ReserveNational Estuarine Research Reserve System (NOAA)Marine Life Protection Act InitiativeThe Partnership for Interdisciplinary Studies of Coastal Oceans (PISCO)
{{Authority control Estuaries of California Bodies of water of Monterey County, California Drainage basins of Monterey Bay Important Bird Areas of California Landforms of Monterey County, California Protected areas of Monterey County, California Ramsar sites in the United States