Chesapeake at risk from Asian oysters
Earlier this year, Virginia officials endorsed a proposal to establish more than a million oysters in Chesapeake Bay. Oysters in the Chesapeake. That’s as natural as maple syrup in Vermont, crawfish in Louisiana, salmon in the Pacific Northwest. Except in this case, the Virginia Marine Resources Commission isn’t looking to restore the native bivalve, Crassostrea virginica, which gets its scientific name from the state. Rather it wants to bring in a new, exotic species from Asia, known as the Suminoe oyster.
The introduction may help increase the population of bivalves in the Chesapeake, at least in the short term, but it’s a risky, unappetizing idea. The farming of exotic oysters and other shellfish is a gateway for invasive species that can harm natural ecosystems.
Aquaculture, the ranching of our oceans, is a relatively new idea. Whereas most of our land animals – think cows and sheep – were tamed thousands of years ago, the majority of marine animals have been domesticated only in the past few decades. Because we’re new at this, we’re bound to make mistakes.
In the western United States, for example, oysterculture has introduced more than 40 exotic species. The predatory oyster drill, Japanese eelgrass, and a seaweed dubbed the oyster thief for its ability to smother shellfish beds were accidentally transplanted along with the bivalves in the last century. The oyster industry in San Francisco Bay, the source of many invasions, has closed. But these and other exotic animals and plants continue to destroy commercial and recreational fisheries, decrease native biodiversity, and impact human health through the transfer of disease.
It isn’t just oysters. In the 1990s, a California firm imported South African abalone in its search for new species to culture. The abalone was contaminated with a parasitic worm that deforms the shells of mollusks, reducing their value. The worms soon spread to nearby rocky shores. The company went bankrupt. The invader was stopped in its tracks only after more than 1.5 million potentially infested native mollusks were removed by hand along southern California’s coasts. The eradication was a rare success.
Now about those “Pacific” salmon. If you grill a pink slab of salmon from the West Coast this summer, you’re likely barbecuing a farm-raised finfish, introduced from the Atlantic. The domesticated Atlantic salmon is often raised in open pens from Alaska to the Pacific Northwest. More than half a million have already escaped. They’ve been found in the wild in 77 Canadian rivers, competing and interbreeding with native species. As with mollusks, the greatest danger can come in the smallest forms. Parasitic sea lice, imported with farmed Atlantic salmon, may be driving local Pacific salmon, and wild fisheries, to extinction.
Aquaculture can be done well, with native species and careful controls. In Prince Edward Island, Canada, local blue mussels are raised in long stockings suspended in the water column. They grow quickly and have more meat than their wild counterparts. And virginica oysters are being raised in New England and the Chesapeake. It’s still on a small scale, but results are promising, with new businesses opening each year.
There is no quick fix for our estuaries, including the Chesapeake. We’ve overexploited most of our wild marine resources, from oysters to finfish, poisoned them with pollution, or drowned them in sediment. Vast oyster reefs once extended throughout Chesapeake Bay, providing food for local and commercial harvesters, and helping to clean the waters by reducing nutrients and algae. In the 1890s, more than 100 million pounds of oysters were landed each year in the Chesapeake. Nowadays, watermen would be lucky to get a million.
However, the introduction of the exotic Asian Suminoe oyster to the Chesapeake isn’t likely to save the bay. A 2004 report by the National Research Council debunked the myth that the Chinese oyster will rapidly increase production and improve water quality.
In fact, the release of foreign bivalves has been tried before in the Chesapeake. In the 1950s, Japanese oysters were brought in to help the ailing industry. By 1959 an exotic protozoan parasite known as MSX caused massive oyster mortalities. The exotic bivalves never caught on, but that didn’t stop one of their parasites from spreading through what was left of the native oysters on the East Coast. The Chesapeake and its oysters haven’t recovered since.
As aquaculture continues to grow, government funding for aquatic invasive species management needs to be increased. (Almost all federal funding now goes to terrestrial agriculture.) Federal risk assessments should be mandatory before any new species is brought to our shores. All new species should be considered potentially invasive until proven otherwise.
Most importantly, let’s properly manage and celebrate our local cuisine: Dungeness crabs in the Pacific Northwest. Cajun crawfish, Maine lobsters, and Chesapeake oysters. There’s no need to order out.
Joe Roman is a visiting fellow at the Gund Institute for Ecological Economics at the University of Vermont and author of Whale (Reaktion, 2006).