San Dieguito Lagoon State Marine Conservation Area

a waterway winding through lowlands


Located just north of the City of Del Mar in San Diego County, San Dieguito Lagoon State Marine Conservation Area (SMCA) protects the shallow lagoon where the Pacific Ocean meets the San Dieguito River. This SMCA encompasses just more than a tenth of a square mile of brackish estuary and marsh habitat between the San Dieguito Lagoon Ecological Reserve and the main reach of the San Dieguito River. Some ocean fish, such as topsmelt, California halibut, and striped mullet use the tidal wetlands as a nursery, and the salt marsh provides nesting areas for birds like the California least tern. Points of interest include the Grand Avenue Bridge, the Lagoon Boardwalk Trail, and the Coast to Creek Trail.


It is unlawful to injure, damage, take, or possess any living, geological, or cultural marine resource, EXCEPT:
Recreational take of finfish by hook-and-line from shore is allowed. Boating, swimming, wading and diving are prohibited. Closed from 8 p.m. to 5 a.m.

California Code of Regulations Title 14, Section 632(b)(140)(opens in new tab)

Quick Facts

MPA size: 0.11 square miles

Habitat composition*:

  • Estuary: 0.10 square miles
  • Coastal marsh: 0.55 square miles

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

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24 JUN

A round stingray in the San Dieguito Lagoon SMCA


Photo © BJ Stacey, CC BY-NC 2.0

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About San Dieguito Lagoon State Marine Conservation Area

Natural History

a lightly striped fish jumping from the water
A striped mullet jumping in the San Dieguito Lagoon SMCA. Photo © BJ Stacey, CC BY-NC 2.0

Located just inland from the San Diego coastline, this area is typically shielded from storms originating from the north and northwest. Protected from the waves and surf of the Pacific, the calm waters create a sheltered environment for plants and animals. Freshwater from the San Dieguito River, one of the largest rivers in San Diego, mixes with saltwater originating from the Pacific Ocean. Lagoon species evolved to handle these large variations in temperature and salinity.

The ocean waters, filled with plankton and other nutrients, feed the plant life and fish that live here, supporting the ecosystem and maintaining the food chain. More than 20 species of adult and juvenile fish inhabit the lagoon, including spotted sand bass and California corbina. At low tide, benthic invertebrates, essential due to their role in nutrient cycling, are often exposed in the mudflats. These mussels, snails, clams, and crabs provide food for shorebirds and ducks.


Cultural History

waterways wind through lowlands below surrounding hills; a Spanish style house in foreground
A view of the San Dieguito Lagoon SMCA. CDFW photo by J. Kashiwada

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. The Kumeyaay and Luiseño peoples lived in the area for thousands of years before Europeans arrived. As coastal natives, they had access to many marine resources that were fundamental to their survival. Remnants of shell middens (piles of disposed shells) indicate that these hunter-gatherers were dependent on retrieving food from the sea, including abalone, scallops, and clams.

In 1789, Gaston de Portola passed the San Dieguito River Valley on his way to Monterey. Construction near the San Dieguito River mouth occurred with the building of the Southern California Railroad in 1882. Nearly a century later, to protect the lagoon from impending urban development, residents of the City of Del Mar created the San Dieguito Lagoon Committee. A major restoration project ensued, most of which has since been completed. The newly restored wetlands are benefiting many species that depend on the habitat. For instance, ocean fish such as California halibut, kelp bass, staghorn sculpin, and gobies use deeper portions of the lagoon as nurseries, and salt marsh vegetation provides critical nesting habitat for endangered birds like the Belding’s savannah sparrow. In 2012, the lagoon was adopted as an SMCA and is bordered by the San Dieguito Lagoon Ecological Reserve.


view of lagoon from top of fishing pier
Recreational fishing from shore in the San Dieguito Lagoon SMCA.< em>CDFW Photo by L. Kashiwada

Within the San Dieguito Lagoon, visitors can kayak, bird watch, and hike. Fishing by hook-and-line from shore is also permitted. The San Dieguito River Park offers over 65 miles of hiking trails, including the Coast to Crest Trail, an almost five mile out-and-back trail located near Solana Beach. The lagoon's trail and boardwalk stretch for more than a mile, wrapping around the critical lagoon habitat. Designed to allow for periodic flooding during the rainy season, the boardwalk provides visitors with close access to sensitive marsh areas of the San Dieguito Lagoon.

Bring binoculars, this is a birdwatching hotspot with more than 100 resident and migrating species. Grand Avenue Bridge, located off San Dieguito Drive, offers some of the best views of the SMCA. The bridge, built during World War II for access to the U.S. Navy airfield, has been transformed into an interpretive outlook. Outside of the lagoon, where the San Dieguito Rivers meets the Pacific Ocean, surfing, tidepooling, and snorkeling are widely popular.


This area consists of waters below the mean high tide line within the San Dieguito Lagoon Ecological Reserve southeastward of a straight line between the following two points:

32° 58.066' N. lat. 117° 15.579' W. long.; and
32° 58.072' N. lat. 117° 15.548' W. long.

California Code of Regulations Title 14, Section 632(b)(140)

Downloads for San Dieguito Lagoon State Marine Conservation Area


Map of San Dieguito Lagoon State Marine Conservation Area - click to enlarge in new tab

Facts, Map & Regulations

MPA fact sheet - click to enlarge in new tab