Tijuana River Mouth State Marine Conservation Area

aerial view of river estuary and its passage to the sea


Tijuana River Mouth State Marine Conservation Area (SMCA), California’s southernmost marine protected area (MPA), protects around three square miles of habitat beginning at the United States/Mexico border and extending north towards Imperial Beach in southern San Diego County. The SMCA protects varied ecosystems, including sandy beaches, tidal flats, coastal marsh, surfgrass and kelp beds, sandy seafloor, and the largest offshore cobble reef in the south coast region.

This MPA sits adjacent to the Tijuana River National Estuarine Research Reserve. The combination of onshore/offshore protection helps to maintain the connection between the estuary and marine environments, keeping this large Southern California ocean-estuary complex intact. Tijuana River Mouth SMCA is a popular location for birdwatching as it is frequented by more than 370 species of birds, including marbled godwits, sanderlings, western sandpipers, double-crested cormorants, California brown pelicans, and a variety of gulls and terns. California halibut use the adjacent estuary as a nursery and move offshore into the open ocean SMCA when older, and gray smoothhound sharks move between the MPA and estuary looking for meals like small fish, ghost shrimp, and innkeeper worms.


It is unlawful to injure, damage, take, or possess any living, geological, or cultural marine resource, EXCEPT:

Recreational take of coastal pelagic species except market squid (northern anchovy, Pacific sardine, Pacific mackerel, and jack mackerel), by hand-held dipnet only is allowed. Commercial take of coastal pelagic species except market squid, by round-haul net is allowed. Not more than five percent by weight of any commercial coastal pelagic species catch landed or possessed shall be other incidentally taken species, including market squid.

California Code of Regulations Title 14, Section 632(b)(147)(opens in new tab)

Quick Facts

MPA size: 3.02 square miles

Shoreline span: 2.2 miles

Depth range: 0 to 55 feet

Habitat composition*:

  • Sand: 2.89 square miles
  • Rock: 0.08 square miles

*Habitat calculations are based on 3-dimensional area and may exceed the total MPA area listed above.

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About Tijuana River Mouth State Marine Conservation Area

Natural History

seabird in flight holding prey in beak
Least tern flying through the Tijuana River Mouth SMCA with prey. photo © hikingsandiego, CC BY-NC 2.0

Tijuana River Mouth SMCA sits at the southern edge of California, bordering Mexico, and includes a variety of unique marine and estuary ecosystems. The large sandy beaches along shore support native plants and provide nesting habitat for birds, including the endangered western snowy plover. The estuary and wetlands, where the river and ocean meet, host fish including leopard sharks, flounder, skates, and rays while also serving as nursery grounds to rockfish, halibut, and various invertebrates. Rocky reefs support California spiny lobsters, schooling sardines and anchovies, and an important spawning area for barred sand bass, a popular Southern California sport fish.

The SMCA lies adjacent to the Tijuana River National Estuary, a National Estuarine Research Reserve site and Southern California’s only coastal lagoon not divided by roads and rail lines. With more than 90 percent of Southern California wetlands destroyed by development and other land use changes, Tijuana River Estuary is one of the few intact salt marshes remaining. This area is considered an essential breeding, feeding, resting, and nesting ground for more than 370 species of migratory and resident birds. In addition to more common species like western gulls, brown pelicans, black-bellied plovers, and willets, the area hosts sensitive species such as California least terns and light-footed clapper rails, which have experienced population declines due to loss of appropriate habitat.


Cultural History

Pismo clam shell on the sand
The Kumeyaay used Pismo clam shells as scoops and spoons. photo © hikingsandiego, CC BY-NC 2.0

For centuries, Native American Tribes in California have relied on marine and coastal resources. Many Native American Tribes in California continue to regularly harvest marine resources within their ancestral territories and maintain relationships with the coast for ongoing customary uses. This culturally rich area is home to the Kumeyaay people, and members of the Kumeyaay’s southern branch, known as the Tipai, lived near the estuary seasonally and thrived on local resources.

The first European colonizers were soldiers, explorers, and missionaries. Soon after settlement, the San Diego Presidio and San Diego Mission were established in 1769. In 1848, when the Treaty of Guadalupe Hidalgo was signed, the homelands of the Kumeyaay were split, leaving part of their people on either side of the U.S.-Mexico border. In October 1849, members of a joint U.S.-Mexico International Boundary Commission met at a location overlooking the Tijuana River Estuary to begin demarcating the United States/Mexico International Border.

By 1929, the United States Navy had acquired land around the estuary. The Navy called its first leasehold “Border Field”, which was used as a gun range and training ground throughout World War II. In 1961, the Navy decommissioned Border Field, and ten years later, 372 acres were established as Border Field State Park. In 1974, the International Boundary Monument was placed on the National Register of Historic Places and the southern portion of the estuary was afforded protection. In the years following, community members came together to defeat plans for channeling the Tijuana River for use as a marina, and in 1980, the unfragmented estuary was designated the Tijuana Slough National Wildlife Refuge, which now borders the MPA established in 2012.


children play a length of seaweed on the beach in front of border wall
Children holding kelp wrack on the beach. photo © B. Auer, CC BY-NC 2.0

Visitors can access this protected area from Seacoast Drive in Imperial Beach, just north of the SMCA, or from the Tijuana River National Estuarine Research Reserve/Border Field State Park. While the beachfront is not popular among swimmers or surfers due to hazardous conditions such as rip currents and a lack of lifeguards, there are excellent opportunities for hiking, photography, birdwatching, and horseback riding adjacent to the SMCA. 

Certain recreational and commercial fishing is permitted, including take of coastal pelagic species (except market squid). Visitors can also explore Tijuana River National Estuarine Research Reserve and the Tijuana Slough National Wildlife Refuge to learn about the area’s wetland and coastal life. The southern portion of the SMCA is next to Border Field State Park, which offers amenities including picnic areas, restrooms, barbeques, horse corrals, and scenic views.



This area is bounded by the mean high tide line and straight lines connecting the following points in the order listed except where noted:

32° 34.000' N. lat. 117° 07.980' W. long.;
32° 34.000' N. lat. 117° 09.000' W. long.;
32° 31.970' N. lat. 117° 09.000' W. long.; thence eastward along the U.S./Mexico Border to
32° 32.064' N. lat. 117° 07.428' W. long.;

California Code of Regulations Title 14, Section 632(b)(147)

Downloads for Tijuana River Mouth State Marine Conservation Area


Map of Tijuana River Mouth State Marine Conservation Area - click to enlarge in new tab

Facts, Map & Regulations

MPA fact sheet - click to enlarge in new tab