Oysters are frequently cultivated for food and pearls. Many people are growing oysters for people to eat. Oyster aquaculture (farming) is a growing industry. China, South Korea and Japan are the world’s largest producers of oysters. The oyster industry in many places has collapsed, The Chesapeake bay for example yields only 80,000 bushels a year, down from a peak of 15 million in the 19th century. As natural oysters became overharvested oystermen began farming fast-growing Pacific oysters which originate in Japan. This species now account for 90 percent of the oysters raised n Britain. Europe’s native flat oyster is said to have a better taste.
Some oysters are still harvested in the wild but places they were once plentiful are now overfished. The Jigozen oysters caught at Jigozen Port in Hatsukaichi in Japan are famous throughout the country. Even these are now farmed. One oyster farmer told the Yomiuri Shimbun. “The sea off Jigozen provides good quality phytoplankton for the oysters to feed on. That’s why they are so tasty...At the peak of the oyster season in January and February well-fed oysters become so fat they nearly pour form their shells.”
In the U.S., the wild oyster harvest is managed by individual states or other jurisdictions. Similarly, aquaculture permitting is run by states. Guidelines and procedures vary from state to state. In some areas, NOAA scientists collaborate with state and other resource managers. They provide the most up-to-date science to help the resource managers make decisions and set regulations. [Source: NOAA]
NOAA supports science that resource managers and decision makers can use as they set regulations about wild oyster harvest and aquaculture operations. NOAA science also helps practitioners who are restoring oyster reefs learn about the best ways to make their work effective and efficient.
Websites and Resources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Fishbase fishbase.se ; Encyclopedia of Life eol.org ; Smithsonian Oceans Portal ocean.si.edu/ocean-life-ecosystems
Oysters are grown in tidal areas. They can be grown directly on the beach bottom or in mesh bags, trays or cages that are either anchored in the water column or floated on rafts. Growing oysters requires no feed — they filter phytoplankton directly from the water column. Oysters provide net environmental benefits by removing excess nutrients and improving water quality. Shellfish toxins and bacteria occur naturally in the environment and can cause foodborne illnesses. State and federal regulations require monitoring of farmed oysters to ensure they are safe to eat. [Source: NOAA]
Joel K. Bourne, Jr. Wrote in National Geographic: “Perry Raso of Matunuck, Rhode Island, farms a monoculture, not a polyculture, but he doesn’t feed his aquatic animals anything at all — and he’s got 12 million of them. Raso is an oyster farmer, one of the new generation of shellfish growers who’ve been blessed by virtually everyone, from the Monterey Bay Aquarium Seafood Watch program to the new Aquaculture Stewardship Council, which recently published its first standards for shellfish. A key to sustainability, these groups say, is learning to eat farther down the food chain. Shellfish are just one step up from the bottom. And besides producing a healthy product low in fat and high in omega-3s, shellfish farms clean the water of excess nutrients. Raso started his farm his senior year of college and was soon selling his oysters at farmers markets. [Source: Joel K. Bourne, Jr., National Geographic, June 2014]
Oysters cement their left hand valve directly onto surfaces such as rocks, shells or mangrove roots. The successful farming of oysters and other shellfish relies upon successful settlement of larvae onto a selected substrate — typically other oyster shells or ceramic tiles — within a hatchery or wild setting. The tiles or shells that hold the spat are secured to frames or in cages and submerged along an intertidal area or suspended from a long line. From this point forward, the oysters are self-sustaining, filtering all the nutrients they need directly from the water in their environment.
Oysters from Hiroshima Prefecture account for about 60 percent of Japan’s catch. At the port there fishing vessels leave at 4:00am and arrive 10 minutes later at the oyster beds. There the ship’s crane is used to pull up the oyster-covered wire cages from the sea. Oysters can be harvested at a rate of up to 60,000 an hour. They are soaked in seawater for 24 hours to clean them. The are shucked with a hook-shaped tool mainly by women in rubber gloves and hairnets. Unshelled oysters are steamed for a few minutes in white wine and served at restaurants in the area.
In the U.S. Permitting for shellfish aquaculture is governed by federal, state and local governments. The federal agencies involved are NOAA, the Army Corps of Engineers, U.S. Fish and Wildlife Service, U.S. Department of Agriculture, the Environmental Protection Agency, the Food and Drug Administration, the Bureau of Ocean Energy Management, and the Coast Guard. Shellfish farms must adhere to federal regulations including those in the Magnuson-Stevens Fishery Conservation & Management Act, the Endangered Species Act, the National Environmental Policy Act and the Clean Water Act. [Source: NOAA]
According to a study lead by Michael Beck of the University of California approximately 85 percent of the world’s native oysters have disappeared from estuaries and bays. Vast reefs and beds of oysters once lined estuaries around temperate regions of the world. Many were destroyed by dredges in a rush to provide cheap protein in the 19th century. The British consumed 700 million oysters in the 1960s. By the 1960s catches had fallen to 3 million. In Britain millions of oysters have been killed by a herpes virus. Elsewhere in Europe native flat oysters have been wiped out by a mysterious disease.
Centuries ago, eastern oysters were plentiful. In some places, reefs were so big that ships had to navigate around them. Since then, in many areas, the populations have dwindled to just a few percent of what they once were. This is due to disease, overharvesting, habitat loss, and poor water quality. These continue to be threats along with changing conditions due to climate change. [Source: NOAA]
People are working hard to rebuild oyster populations. NOAA and its partners are working to restore the healthy oyster reefs that so many other species rely on for habitat. In the Chesapeake Bay, for example, NOAA and partners are involved in the world’s largest oyster restoration effort. There, they have restored nearly 1,100 acres of oyster reef.
Ancient Chesapeake Bay People Sustainably Harvested Oysters
Indigenous peoples in the Chesapeake Bay area harvested oysters sustainably for thousands of years. It wasn’t Europeans arrived and introduced new techniques of harvesting them that oyster stocks declined. Evan Lubofsky wrote : As long as 3,200 years ago, Indigenous peoples living along the banks of the Chesapeake Bay harvested oysters in vast quantities. They extracted the meat and piled the shells into mounds known as middens. “Despite the significant role oysters played in the Native American diet back then, they weren’t overexploited,” says archaeologist Alex Jansen, leader of a recent study analyzing the middens. “Even though it is possible that these early societies may not have been practicing sustainable harvesting intentionally, it appears they were able to balance management with fishery needs,” Jansen adds. “That’s something we need to get back to.” [Source: Evan Lubofsky, Hakai magazine.com, December 2018]
Examining shell middens near Chesapeake Bay showed Jansen that the Indigenous peoples’ harvesting practices were much less destructive, which is what allowed them to exploit oysters for thousands of years. Jansen also found tools such as ceramics, projectile points, and stones used for heating water at the study site. But based on his analysis, these tools were not used for oyster harvesting, which, he says, was mostly done by hand. He also noted the large sizes of the oyster shells, which suggests the oysters were given time to grow and reproduce before being snagged.
Throughout the thousands of years captured in the shell middens, “the oysters were largely consistent in shape and size,” Jansen says. He says the oysters were likely harvested from the water close to shore, rather than from deeper waters where reefs form. “By leaving the reefs alone and intact, Native American harvesters were able to give the oysters a chance to reproduce and restock the bay.”
Combating Red Tides with Oysters
In recent years, NOAA's National Centers for Coastal Ocean Science (NCCOS), in collaboration with NOAA's Northeast Fisheries Science Center, has enlisted estuaries' indigenous residents, namely, bivalve mollusks, to help slow and, in some cases, reverse the process of eutrophication, since they efficiently remove nutrients from the water as they feed on phytoplankton and detritus. [Source: NOAA]
A groundbreaking modeling project in Long Island Sound showed that the oyster aquaculture industry in Connecticut provides $8.5–$23 million annually in nutrient reduction benefits. The project also showed that reasonable expansion of oyster aquaculture could provide as much nutrient reduction as the comparable investment of $470 million in traditional nutrient-reduction measures, such as wastewater treatment improvements and agricultural best management practices.
The NOAA scientists used aquaculture modeling tools to demonstrate that shellfish aquaculture compares favorably to existing nutrient management strategies in terms of efficiency of nutrient removal and implementation cost. Documenting the water quality benefits provided by shellfish aquaculture has increased both communities' and regulators' acceptance of shellfish farming, not only in Connecticut but across the nation. In Chesapeake Bay, for example, nutrient removal policies include the harvesting of oyster tissue as an approved method, and in Mashpee Bay, Massachusetts, cultivation and harvest of oysters and clams are part of the official nutrient management plan.
Man Dies of Vibriosis after Eating Raw Oysters
In June 2023, a 54-year-old Missouri man died of vibriosis after he ate raw oysters he purchased from a seafood stand, authorities said. TODAY reported: The man died after he was infected with the bacteria Vibrio vulnificus, which can be carried in oysters and other shellfish, according to St. Louis County Department of Public Health. County health department investigators found the man ate the oysters sometime in the week before his death. He was treated at an area hospital and died. "There is no evidence that the business did anything to contaminate the oysters, which likely were already contaminated when the establishment received them," health department investigators said in a press release. [Source: Anna Kaplan, TODAY, June 13, 2023]
Symptoms of vibriosis include abdominal cramping, nausea, vomiting, fever and chills, according to the St. Louis County Department of Public Health. The department noted severe illness and death from vibriosis is rare and typically occurs in people with a weakened immune system.
The Centers for Disease Control and Prevention said people can reduce their risk of vibriosis by following these tips: 1) Always cook oysters or other shellfish before eating: Don’t eat them raw or undercooked. 2) Always wash your hands with soap and water after handling raw shellfish. 3) Avoid cross-contaminating cooked shellfish with raw shellfish and its juices.
Image Sources: Wikimedia Commons, NOAA
Text Sources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.
Last Updated April 2023