| The Magazine of the CALIFORNIA ACADEMY OF SCIENCES |
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Horizons Return of the Native Oyster
San Francisco has been a gourmet town from the very beginning. When the original Forty-Niners roared into town, pockets sagging with gold dust, the prospectors celebrated in the saloons of the Barbary Coast-with French champagne and native oysters. And even before the prospectors arrived, the local Ohlone people savored the oyster as a staple food, piling the shells into giant middens for thousands of years. Raked fresh from the bay by the boatload, these corrugated beauties soon became as symbolic of San Francisco as sourdough bread. Known as Olympia oysters after Washington's Olympic Peninsula, the shells of the largest grew to the size of a silver dollar. To miners, the Olys were just as satisfying to possess. Their coppery, metallic taste was reminiscent of the belon, a close relative prized in French haute cuisine. Entrepreneurs
packed live local oysters into barrels of seawater and delivered them
to the goldfields by pack train. There, folded into bacon omelettes by
a creative Placerville cook, they Hangtown Fry's hefty price tag may have been due to the work of shucking as much as the cost of shipping. The same gallon bucket which could hold several hundred shelled Eastern oysters needed several thousand petite natives to fill it. Slow to grow and erratic breeders, the bay's native oysters were no match for the appetites of the gold-diggers. Oyster hunters soon stripped every live animal they could find from beds that once stretched from San Mateo to Oakland. Even worse, the acres of oyster reefs built up over millennia were now buried beneath Sierra silt. Whole hillsides blasted loose by hydraulic mining were washed downstream into the Bay, transforming once-rocky shorelines into gooey muck. The onslaught left Ostrea conchaphila, the shell-loving oyster, unable to find hard surfaces such as other oysters on which to settle and grow. By 1900, native oysters were essentially gone from San Francisco Bay. Nearly a century later, in 1990, an empty shell dropped by a seagull found its way into the hands of a Bay Area marine biologist. The biologist nearly fell over in shock. The legendary Olympia oyster had survived. A quick survey turned up remnant populations from China Camp in Marin to Coyote Point in San Mateo clinging to bricks and tires, landscaping gravel, and even pier pilings-anything solid enough to call home. "It seems like they were just barely staying ahead of extinction," says fisheries biologist Michael McGowan. "There were little populations here and there that would reproduce, and eventually go locally extinct, but some larvae would land and begin the cycle again elsewhere." The discovery aroused half-forgotten dreams in the hearts of local marine scientists. Here was the chance to resurrect an organism that had once played a major role in local food webs into a functioning part of the modern ecosystem. Today, a core group of researchers, government agencies, nonprofit groups, and community volunteers is working to return California's native oyster to local waters. Still in its infancy, the project might appear a charming sideline in the much larger movement to resuscitate San Francisco Bay. In fact, the long-term biological health of this complex estuary could depend in part on the success or failure of the unassuming Oly. For the last five years, Ted Grosholz has been trying to piece together the role oysters once played in bay ecology. "We don't really know what the system looked like a century ago. We do know that oysters were a really important part of the bay," he says. "They improved water quality, and created habitat for invertebrates and small fishes," says the University of California, Davis marine biologist. Though tiny, each Olympia filters between 5 and 25 gallons of water per day to capture enough plankton to survive. Multiply that by the millions of oysters that once ringed the bay, and their dining habits likely kept even stagnant corners of the bay free of toxic algal blooms. The reefs of empty oyster shells that once carpeted the bay's subtidal zone were equally vital. They rose from the muddy bottom like high-rise apartments, 30 feet deep in places, creating a whole new type of habitat. "If you approach a big mound of shell from the perspective of a tiny marine organism, there is an enormous number of nooks and crannies to hide from predators and pounce on prey," says Paul Olin, a marine advisor with UC Extension and California Sea Grant. "It's no wonder there's a teeming marine community associated with shell reefs." Restoring oysters to a semblance of their former strength could be instrumental for natives struggling against the tsunami of exotic species that has invaded the bay. "The idea is that native species evolved with oyster habitat and are able to use that more effectively than nonnative species. Our hope is that we can tip the balance and increase the abundance of native species at the expense of the exotics," Grosholz says. Scientists are now trying to recreate this disappeared habitat and improve conditions for native oysters at the same time. In 2000, McGowan and Marilyn Latta, habitat restoration manager for the nonprofit group Save the Bay, teamed up to see whether they could get wild oysters to settle and grow. Aided by teams of community volunteers and a grant from the National Oceanic and Atmospheric Administration (NOAA), the researchers strung rope necklaces with clean Pacific oyster shells and suspended them from pilings at sites from Tiburon's Richardson Bay south to Redwood City. They chose the sites as much for the involvement of neighborhood conservation groups as the presence of existing oyster populations. The volunteers checked the strings once a month to see what had moved in. To their surprise, success arrived in one of the bay's most polluted and industrial pockets. "It's amazing to me that more than 200 oysters, plus 20 other species, found our shells at the mouth of Sausal Creek in the Oakland Estuary," says Latta. "We had little tunicate sea squirts, mussels, anemones, sponge colonies-it was like being out at the tidepools." It looked like wild oysters were still spawning, and all they needed was a solid place to lay their shells. Grosholz and Olin have taken the project one step further with funds from California Sea Grant and the National Oceanic and Atmospheric Administration, as well as help from Hog Island Oyster Company and other oystermen. In 2002, they stuffed mesh bags the size of bed pillows full of cleaned oyster shells from oyster farmers and lashed the bags in a pyramid shape onto wooden pallets. They then scattered the pallets on the tidelands around Tomales Bay. The researchers plan to measure not only how many baby oysters will settle per pound of shell, but also how these miniature reefs affect biological diversity. A rich array of creatures is expected to move in, from crabs and shrimps to worms and amphipods no larger than a comma. "These provide the basis for the large food web. Our next step is to see how the beds influence native fishes; if they attract more, then that's likely to have a positive influence on shorebirds and bigger fishes," Grosholz says. Already, preliminary data indicate the pallets are a magnet for local marine life. The scientists are using Tomales Bay as a testing ground for restoration techniques that could be scaled up in San Francisco Bay. The estuaries have a comparable mix of introduced and native species, and oyster settlement and survival requirements are likely to be similar in both places. Urban runoff and industrial and agricultural pollution mean that San Francisco Bay oysters are not likely to be edible anytime soon. But Tomales Bay, already home to a thriving oyster fishery, could realistically provide wild Oly meals in the foreseeable future. McGowan and the Tiburon Audubon Center started a similar project in Richardson Bay just this spring. "Our goal is to try to restore the system to close to what it was when all the bay organisms evolved here," McGowan says. Few oysters have settled yet in either experiment, but researchers say they have every reason to be optimistic. After all, the project they hope to launch in San Francisco Bay is already underway in another major estuary 3,000 miles to the east. For millennia, Chesapeake Bay yielded hundreds of thousands of pounds of oysters each year for hungry Native Americans, European colonists, and generations of oyster fishermen. Then, in the first half of the twentieth century, the bay's native Crassostrea virginica oysters began dying from introduced diseases. The once-glassy waters of the bay grew so cloudy that waders in knee-deep water could no longer see their feet. The oyster population that filtered the volume of the entire bay in a few days has dwindled to the point where it cleans the Chesapeake roughly once a year. Now the Chesapeake Bay region is in the midst of a large-scale push to reverse the trend. Workers clean commercially grown oyster shells by the ton, load them in great piles on barges, and blast them into the bay with firehoses. At other restoration sites, they stuff hundreds of mesh bags with shells and pile them into head-high reefs that encompass entire stretches of shoreline. At this stage, the project is starting to improve local water quality. The bay's waters are measurably cleaner after flowing across the reefs, says oyster researcher Roger Mann of the Virginia Marine Institute. In the West, says Mann, "if people provided enough structure, it could kick start the process. We just need to lift them up a little bit above the muck." For their part, local researchers predict that healthy populations of oysters could take root within the next decade, given the right political climate, community interest, and restoration funds. "Oysters are down, but not out," McGowan says. "They can make a comeback." Kathleen M. Wong is Senior Editor of California Wild. |
