Oysters, Pirates, and Pollution

Historical Essay

by David D. Schmidt, 2026

An excerpt from the book, San Francisco Bay Area: An Environmental History, by David D. Schmidt (Backcountry Press, 2025).

Oyster pirates in the San Francisco Bay, c. 1900.

Photo: jstor

For thousands of years, the Bay Area’s native tribes harvested native Olympia oysters and clams on the Bay’s intertidal mud flats and gathered mussels clinging to rocks. Olympia oyster shells were found in most of the 400+ shellmounds (former village sites) around the shores of San Pablo and San Francisco Bay.

The commercial oyster industry began with the Gold Rush. John Stillwell Morgan arrived in California in 1849 and began raking up oysters from the bay's shallow waters to sell in San Francisco. Demand for oysters jumped when a cook in Placerville in the Sierra foothills, then known as Hangtown, served an omelette with bacon and oysters to a condemned prisoner who requested it for his last meal. “Hangtown Fry” soon became a restaurant specialty all over the state. It’s been on the menu continuously for more than 170 years at San Francisco’s historic Tadich Grill.

In the first years of the Gold Rush, barrels of live Olympia oysters were brought from oysterbeds in the bay’s tidal mudflats to San Francisco and Sacramento by boat, with some of the oysters sent on to mining towns like Placerville by mule train. By 1851, local oysters were scarce, so Morgan looked elsewhere. He found them in Shoalwater Bay in Washington State. In March 1852, he brought his first shipload of Olympia oysters into the bay, and planted them on mudflats off Sausalito to keep them alive until he could sell them.

In the 1850s and 1860s, Morgan's company alone shipped 50,000 bushels of the four-inch long oysters each year from Willapa Bay, Washington to San Francisco. By the 1860s, however, hydraulic mining in the Sierra Gold Country was washing vast amounts of sediment downstream into the North Bay, often smothering the oysters. Morgan abandoned his North Bay oyster beds in the 1870s in favor of South Bay mud flats.

From 1870 to the early 1900s, Morgan and others imported railcar loads of oyster "seed" (baby oysters), from the larger Eastern oyster (which can grow to 10 inches), via the Transcontinental Railroad. Eastern oysters didn’t spawn in the bay because the water was too cold, so the industry remained dependent on oyster seed from the Eastern U.S.—an average of 124 railcar loads per year in the 1890s.

Jack London’s “Raid on the Oyster Pirates”

In Jack London's short story, "A Raid on Oyster Pirates," the narrator, a young man based on London himself, is a deputy fish warden who infiltrates a band of thieves on an Oakland wharf. In the story, he carries out a daring plan to steal their boats while they're stealing oysters on the South Bay mudflats, stranding them between a rising tide and a sheriff's posse onshore. London had first-hand experience with oyster piracy, but in reality he had been one of the "pirates."

During the peak years in the late 1800s, oyster growers used more than 40 square miles of the bay’s tidal mudflats—nearly the area of San Francisco. The oysterbeds were fenced to keep out predators such as bat ray fish, and to mark ownership boundaries. Since they were often unguarded at night, thieves with small sailboats or rowboats—grandiosely termed "oyster pirates" by London—tried to sneak in and fill sacks with oysters, then bring them back to Oakland or San Francisco to sell.

In addition to local sales of live oysters, the bivalves were cooked, canned and shipped to customers nationwide. In the 1890s, they were the state's most lucrative seafood product, outselling salmon. Production peaked in 1895 at approximately 15 million pounds, with Morgan’s Millbrae mudflats (later filled in, now San Francisco International Airport) accounting for most of it. Morgan had bought out all but one of his competitors by 1886, gaining a near-monopoly.

By 1899, however, the oyster haul fell to 2.7 million pounds. No one knew why, but oysters just wouldn't grow in the South Bay any more. By this time, almost all the oysters were coming from Morgan's oyster beds at Millbrae. Production continued falling to 729,000 pounds in 1908—a horrendous 95% drop in 13 years. Oyster growers noticed that many of the larger ones were dying. The rest were thin and watery. The Morgan company had to start importing more expensive full-grown oysters because they would no longer grow from “seed” in the bay.

Oyster production in the bay recovered somewhat over the next few years, then headed downward again to less than 400,000 pounds in 1932 and 1933. By this time, oyster growers were shifting operations to the cleaner waters of Sonoma County’s Bodega Bay and Marin County’s Drakes and Tomales Bays.

In 1923, John S. Morgan's successor F. C. Morgan sold most of the company's 40 square miles of bay mudflats and shallows to the Pacific Portland Cement Company, which dredged up oyster shells lining the bay bottom to use as an ingredient in cement at their Redwood City plant (later known as Ideal Cement). In the early 1900s, oyster shells that had washed up on the bay’s shoreline over thousands of years formed a white, glistening beach of sun-bleached shells that extended south from San Mateo for at least a dozen miles. By the 1970s, however, bay filling and cement manufacturing had reduced these shell beaches to a few small fragments.

The cause of the oyster’s decline had been a mystery. In recent years, however, biologists noted that the oysters’ demise coincided with the growth of fruit and vegetable canneries in the Santa Clara Valley. The canneries dumped spoiled fruit and trimmings into sewers, which channeled the untreated, nutrient-rich effluent into the South Bay, stimulating algae growth, whose decomposition robbed the water of oxygen, stressing or killing fish and oysters. During the fruit canning season each summer and fall from the early 1900s to the mid-1960s, bay waters south of the Dumbarton Bridge were stinking and lifeless.

In 1932, sewage-contaminated oysters and clams from the bay were found to be the cause of typhoid fever. In July of that year, Doctors J. C. Geiger and J. P. Gray published an article in the journal California and Western Medicine that definitively linked typhoid outbreaks to contaminated shellfish. The San Francisco Department of Public Health closed areas near sewage outfalls to recreational shellfish harvesting. Local demand for all bay shellfish suddenly dropped as a result of the publicity.

One company owned by two major San Francisco fish dealers, A. Paladini Inc. and F. E. Booth Inc. (the sardine canner), continued to grow oysters on mudflats at the present-day site of SFO, and at Oyster Point (part of South San Francisco) in the 1920s and 1930s. But commercial oyster harvesting in San Francisco Bay ended completely by 1939.

The earliest commercial oysterbeds in Marin’s Tomales Bay dated to 1875, but it wasn't until the failure of San Francisco Bay's oysters that industry there took off. The California Department of Fish and Game and the U.S. Bureau of Fisheries encouraged oyster growers to import Pacific oyster "seed" from Japan starting in 1930, and grow this jumbo-sized (up to 12-inch) oyster in calm tidal waters along the coast. Thanks to growers at Bodega Bay, Tomales Bay and Drake’s Estero, the Bay Area produced more oysters than the rest of California combined until 1943.

In December 1941, the war with Japan abruptly cut off access to Pacific oyster seed. Bay Area production plummeted 75% in 1942, and another 79% by 1946. Local production inched back up to half a million pounds by 1957, but this was dwarfed by the statewide harvest of 11.3 million pounds that year.

Oyster growing continues in Tomales Bay, but pollution can still be a problem. In the summer of 1997, state health officials closed the bay to shellfish harvesting for three weeks because oysters were contaminated with the bacteria Vibrio parahaemolyticus, which causes debilitating diarrhea, abdominal cramps, nausea, vomiting, headache, fever, and chills. Even today, raw oysters can be hazardous to your health. They must be cooked to an internal temperature of at least 145 degrees to kill bacteria, which proliferate in warm waters every summer. Though Tomales Bay’s human population is small, three pollution sources there can contaminate oysters: Leaky septic systems connected to bayside homes, illegal flushing of boat toilets into the bay, and cow manure from dairies.

In San Francisco Bay, sewage treatment plants cleaned up the bay’s shallow waters by the late 1970s. Since 1982, the California Department of Health has found the bay clean enough to allow recreational shellfish harvesting during the summer along the San Mateo County shoreline between Coyote Point Yacht Harbor and Ryder Park, but only a few people venture out to collect them. The bay still isn’t clean enough to reliably produce safe oysters for commercial harvesting. Oysters grown there would have to be removed to live in cleaner water for several weeks to purge any contamination before being sold.

And what of the native Olympia oyster, rarely seen after 1870? For more than a century it was presumed extinct. Then in 1990, someone found an unusual shell dropped by a gull, and gave it to a local marine biologist to identify. The biologist was astounded that it was an Olympia oyster, and quickly surveyed rocky outcrops along the San Francisco Bay shoreline to see where the Olympia oyster had survived.

According to San Francisco State University's Romberg Tiburon Center fisheries biologist Michael McGowan, "It seems like they were just barely staying ahead of extinction. There were little populations here and there that would reproduce, and eventually go locally extinct, but some [free-swimming oyster] larvae would land and begin the cycle again elsewhere."

One factor making it tough for Olympia oysters in the bay was the lack of hard surfaces to grow on. Originally, they grew on dead oyster shells, but most of these had been covered with silt during the hydraulic mining era, dredged to make cement, or covered up by fill. With a $30,000 grant, McGowan launched a project in 2003 to bring back the bay's native oysters.

Oyster mesh bags used to grow and harvest oysters in two places in San Francisco Bay in 2010s.

Photo: courtesy Jerry Matos blog

Working with students and Save the Bay volunteers, McGowan created six-foot-long “necklaces” —strings of oysters shells—and hung them from bridges and piers from Tiburon to Redwood City, hoping to attract floating oyster larvae. In the Oakland Estuary, Richardson Bay, and Coyote Point, these necklaces became encrusted with not just baby oysters, but 19 other native species of marine life after being in the water only six weeks. Encouraged by this, McGowan set out pallets with six 40-pound mesh bags of oyster shells on them, permanently moored in five feet of water, to create self-sustaining oyster colonies that provide habitat for fish, worms, sponges and crabs, which are food for larger animals like birds and bat rays. In 2013, a larger, five-year, $2 million experiment in growing Olympia oysters by the California Coastal Conservancy was declared a success after 2 million new oysters were found growing on mesh bags of oyster shells set out in two acres of shallow waters: one near the San Rafael side of the Richmond Bridge, and one near the Hayward side of the San Mateo Bridge.(1)

Clams and Mussels: Gone With The Waste

During the Gold Rush, San Franciscans dug for clams in the tidal mudflats of two inlets that no longer exist: Mission Bay, just south of today’s downtown, and the mouth of Islais Creek, south of Potrero Hill. People liked clams so much that a clam restaurant was established there in 1861. In the 1860s, going to the “Clam House” by horse and carriage on the Plank Road (Mission Street), through the then-rural Mission District, was a popular weekend excursion.

Bayshore and Oakdale, c. 1918, close-up on the Old Clam House restaurant, then the Oakdale Bar.

Photo: OpenSFHistory.org wnp30.0349

Old Clam House at Bayshore Blvd. and Oakdale, 2020.

Photo: Chris Carlsson

The Islais Creek marsh and mudflats were filled in by the 1930s, but the Clam House (now known as the “Old Clam House”) stayed in business. In 2024 it was the oldest Bay Area restaurant still operating at the same location where it began. Clams and mussels were still on the menu, though they have not been harvested commercially from the bay since 1939. As a result of continued bay filling until the 1970s, the shoreline is now more than a mile away from the Old Clam House, and the former tidal mudflats are now covered by industrial buildings and streets.

Longer view in 1918 at the Oakdale Bar, later the Old Clam House restaurant.

Photo: OpenSFHistory.org wnp30.1313

Long before the Spanish colonial era, Native Tribes living along the bay shoreline had harvested the native bent-nose clam. Their shells have been found in huge quantities in the 400+ shellmounds that once marked village sites around the bay.

In the late 1800s, when Chinese shrimp fishermen sailed from more than two dozen shoreline camps, they also began digging up clams in the mudflats. Mussels, too, were harvested: Originally, Native Tribes had gathered the native sea mussel (Mytilus californianus) from rocky outcrops along the bay and coast, such as Pacifica's Mussel Rock. In the late 1800s, people harvested the European bay mussel (Mytilus edulis) along the bay shoreline. These mussels arrived on sailing ships' hulls before the Gold Rush, and spread to shoreline rocks.

The softshell clam (Mya arenaria) was accidentally introduced to the bay along with the first shipments of live eastern oysters brought from New York via the Transcontinental Railroad in 1870. The new clam spread quickly, largely replacing the native bent-nose clam and winning the favor of local seafood lovers. After 1875, when a railroad reached Point Reyes Station, these mollusks were also harvested in Tomales Bay. Between 1880 and 1900, 1 to 3 million pounds of clams and mussels were taken from the bay and sold annually, in addition to people digging them up on weekends for their own use.

In the early 1900s, clam and mussel harvests started declining. By 1918, the harvest fell to a quarter of 1890s levels; by 1930 it fell to just 1/10. At first, the decline was attributed to the popularity of recreational clamming. By the 1930s, however, even clam beds that had been leased and fenced by commercial clam diggers were being lost to pollution and bay filling. One clam bed, on the south side of San Francisco’s Hunter’s Point, was abandoned in 1930 because it was fouled with industrial wastes. Another, on the bay shore at the San Francisco/San Mateo County line, was turned into San Francisco’s city dump in 1931.

World War II delivered the final blow to bay clamming, as hundreds of thousands of people came from across the nation to take jobs in shipbuilding and other war-related industries. The influx of people and industry increased sewage and industrial waste flowing to the bay. Much of the shoreline stank, and few people wanted to eat clams from it. No clams or mussels were harvested commercially in the entire Bay Area after 1948, and even recreational clammers gave up on the reeking mudflats. Instead, they went to Tomales Bay and Bolinas Lagoon, where the water was still relatively clean. In recent years, clamming has remained popular only north of Tomales Bay.

Questions? Email the author: davidnaturesf@gmail.com

Notes

1. Fimrite, Peter, “2 million oysters in bay begin restoration effort,” SFGate.com (San Francisco Chronicle), Nov. 15, 2013

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Excerpted from David D. Schmidt's San Francisco Bay Area: An Environmental History. Available from Backcountry Press.