Duxbury Reef State Marine Conservation Area

cliffsides adjacent to exposed rock sea floor


Duxbury Reef State Marine Conservation Area (SMCA) sits at the southern end of the Point Reyes peninsula, just a mile west of Bolinas in Marin County. Despite being one of the smallest marine protected areas (MPAs) on the California coast at less than three-quarters of a square mile in area, this SMCA hosts one of the largest shale reefs in North America. Duxbury Reef was selected for inclusion in the statewide MPA network in part due to the extensive tidepool network that forms on the shale reef at low tide.

Numerous intertidal animals live in the tidepools, including turban snails, anemones, sea stars, small fishes such as blennies, and nudibranchs, which are tiny, colorful sea slugs. Today, the tidepools remain one of the most expansive and accessible examples of intertidal habitat in the region, due to the wide, flat intertidal zone that exposes a diverse array of creatures to extreme environmental conditions. The reef is named for the schooner Duxbury, a three-masted ship loaded with gold-seekers that wrecked on the reef in 1849.


It is unlawful to injure, damage, take, or possess any living, geological, or cultural marine resource, EXCEPT:
Recreational take of abalone, and finfish from shore only, is allowed. Please note that the abalone fishery is closed until at least 2026(opens in new tab).

California Code of Regulations Title 14, Section 632(b)(50)(opens in new tab)

Quick Facts

MPA size: 0.69 square miles

Shoreline span: 2.8 miles

Depth range: 0 to 10 feet

Habitat composition*:

  • Sand/mud: 0.06 square miles
  • Rock: 1.52 square miles

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

Photo Gallery


Ten-tentacle burrowing anemone in Duxbury Reef SMCA


photo © R. Johnson, CC BY-NC 2.0

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Video Gallery

California's MPA Network

About Duxbury Reef State Marine Conservation Area

Natural History

colorful sea slug
Three-lined aeolid in Duxbury Reef SMCA. photo © A. Young, CC BY-NC 2.0

Duxbury Reef is an exceptional geologic feature due to its large area and shallow depth. Formation of the reef began millions of years ago as silica-rich diatoms, a type of small plankton, died, sank, and formed thin layers on the shallow sea floor. Over time, the layers of diatoms were compressed to form sheets of fine-grained, silica-rich rock, along with layers of volcanic ash. These layers form the shale in Duxbury Reef.

When the tide is low, fractures in the parallel channels of the shale reef are exposed. These ridges extend out into Bolinas Bay for more than half a mile. Extensive tidepools lined with seaweed teem with animals well-adapted to extreme variations in temperature. During low tide, a wide array of tidepool animals can be seen in the SMCA: mossy chitons, giant green anemones, tiny colorful nudibranchs (sea slugs), small fishes such as gobies and blennies, octopus, porcelain crab, black turban snails, and brittle stars with thread-like legs. Just offshore and to the southeast, the reef recedes to a sandy seafloor; to the north, rocky outcroppings provide anchor points for kelp forests. This exposed bedrock typically supports sizeable forests of bull kelp, a large algae well-adapted to high wave-energy areas. The rocky reef and kelp ecosystems offshore are highly productive and inhabited by lingcod, dozens of rockfish species, cabezon, greenling, and halibut, as well as invertebrates such as sea stars, purple and red sea urchins, giant Pacific octopus, and Dungeness crab.

Duxbury Reef SMCA supports populations of sooty shearwaters, western gulls, common murres, Cassin’s auklets, and many other bird species. Humpback and blue whales are frequently seen in the area; both species are dependent on coastal upwelling to provide the nutrients that support their preferred food sources. Chinook salmon, white seabass, white sharks, and leatherback sea turtles have all been observed in the Duxbury Reef area.

Cultural History

cone-shaped snail shell
Three-colored top shell in Duxbury Reef SMCA. photo © A. Young, 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. The Coast Miwok peoples were the original inhabitants of the Marin County coast, including lands adjacent to Duxbury Reef SMCA. The traditional Coast Miwok diet consists of several species of fish including halibut and rockfish, and invertebrates such as crabs, clams, mussels, abalone and oysters. Kule Loklo, a replica Miwok village run jointly by members of the Coast Miwok and California State Parks, is located near Point Reyes National Seashore Visitor Center.

The first European landing in northern California occurred on June 17, 1579 on the southern side of Point Reyes, now known as Drakes Estero, by the Sir Francis Drake Expedition. Originally used as a safe harbor for trading vessels, the fertile land soon became home to Spanish settlement during the Missionary period until Mexico gained its independence from Spain in 1821. Point Reyes was then used as ranch land and dairy pasture, undergoing several ownership changes until 1962, when much of the land was purchased by the National Park Service for conservation purposes.


rocky seashore at low tide
Low tide at Duxbury Reef SMCA. photo © J. Merz, CC BY-ND 2.0

Duxbury Reef SMCA is a wonderful place to view tidepools, wildlife, and explore the coast. It can be accessed from land along a hiking trail that is ideal for bird and marine mammal watching. Recreational fishermen can take finfish from shore and visitors arriving during low tide have an opportunity to see tidepool invertebrates that are usually hidden from view. At high tide or during large swells, visitors will instead witness thunderous ocean breakers crashing into rocky cliffs.

Visitors should attempt to minimize disturbance to plants and animals living on and between the rocks, and be mindful of their own safety. Never turn your back to the ocean. A “minus tide” of -0.5 to -1.5 feet is required for a successful tidepool adventure. Always check the tides in advance, arrive at least an hour before low tide, and leave no more than an hour after the tide begins to rise. Check the Point Reyes National Seashore website for safety tips on tidepooling.


This area is bounded by the mean high tide line, a distance of 1,000 feet seaward of mean lower low water, and the following points:

37° 55.514' N. lat. 122° 44.179' W. long.;
37° 55.420' N. lat. 122° 44.310' W. long.;
37° 53.650' N. lat. 122° 41.910' W. long.; and
37° 53.770' N. lat. 122° 42.020' W. long.

California Code of Regulations Title 14, Section 632(b)(50)

Downloads for Duxbury Reef State Marine Conservation Area


Map of Duxbury Reef State Marine Conservation Area - click to enlarge in new tab

Facts, Map & Regulations

MPA fact sheet - click to enlarge in new tab