By C. Greg Lutz, Pramod Sambidi and R. Wes Harrison, Louisiana State University Agricultural Center.
Profile updated June 2011 by Diane Huntrods, AgMRC, Iowa State University.
Revised April 2012 by C. Greg Lutz, Louisiana State University Agricultural Center.
The United States produces two major species of oysters, Crassostrea virginica (the Atlantic oyster or Eastern oyster) and the non-native Crassostrea gigas (Pacific oyster). The Eastern oyster, found primarily in the Gulf of Mexico (Gulf Coast) region and the Chesapeake Bay region, historically accounts for roughly 75 percent of total U.S. harvests. The Gulf Coast region, principally Louisiana, generally leads the nation in oyster production. The Pacific region, principally the state of Washington, follows closely, and the Chesapeake region, principally Maryland, ranks third.
Oysters are typically produced in one of three different ways: natural, managed and cultivated. Natural oysters grow and reproduce without human intervention and are often available for harvest by anyone with the appropriate licenses and permits. In contrast, managed oysters are supervised by harvesters who scrape the oyster beds periodically to reduce clustering. In the case of cultivated oysters, immature oysters are transported to man-made beds where they are allowed to mature. In the Northwest and Northeast, a significant amount of shellstock oysters are produced on cultivated beds, while in Gulf Coast waters, they historically have been largely harvested from wild reefs (Muth et al. 2000). Following a series of man-made and natural disasters over the past decade, interest in hatchery production and off-bottom oyster culture is increasing in the Gulf region.
National Marine Fisheries Service (NMFS) figures indicate in that in 2010, U.S. oyster landings totaled 28.1 million pounds (of meats), down from the 2009 figure of 35.6 million pounds of meats. Oyster landings in 2010 were valued at almost $117.6 million, down from the 2009 figure of about $136.5 milllion. The Gulf Coast region harvested about 15.5 million pounds of oysters in 2010, accounting for roughly 55 percent of the national total, followed by the Pacific coast region with over 35 percent.
The Chesapeake Bay's oyster industry has seen tremendous declines over the past several decades. Harvests in Maryland have dropped to annual levels of 50,000 bushels or less in recent years, compared to 2.5 million bushels thirty years ago. During the middle of the last century, landings from Virginia waters reached levels as high as four million bushels annually, but recent harvests declined to roughly 20,000 bushels per year. As of 2010, however, oyster growers in Virginia sold over 16 million oysters worth more than $5 million, according to a report by the Virginia Institute of Marine Science (2011). Millions of dollars have been spent on various initiatives to restore populations of the native Eastern oyster in the Chesapeake over the past several decades. Major factors for declining landings over the decades include overfishing, degradation of reefs by commercial fishing methods, deteriorating water quality, high sediment loads and the emergence during the last half-century of two devastating oyster diseases known as Dermo and MSX.
Similar declines may eventually occur in the Gulf coast region as well. Louisiana’s 2009 oyster landings totaled over 1.8 million sacks with a total value of $46.5 million, but in 2010 approximately 934,000 sacks were landed, with a value of slightly less than $22 million. The combined impacts over the past two years of the Gulf oil spill and the release of large volumes of freshwater (to reduce oil spill impacts to coastal marshes in 2010 and from extremely high discharges from spring flooding in 2011) may result in further declines. Oyster fisheries elsewhere in the Gulf region have battled the combined impacts of industrial pollution, red tides, bacterial and viral diseases, and hurricane damage for a number of years.
Generalized Aquaculture Methods
Hatcheries generally use broodstock that have been held on-site and conditioned for maturation and spawning, or wild-collected broodstock during the natural spawning season. Broodstock are induced to spawn through environmental stimuli (primarily temperature). Fertilized eggs develop into larvae, which are cultured primarily with algae (which must be cultivated on-site), and larvae are washed and graded every few days until they become “pediveligers.” These pediveligers are then provided with shell cultch on which to settle en masse, or they may be placed in specialized tanks with finely ground oyster shell particles on which they settle individually. A suitably sized hatchery can supply several to many oyster culturists.
Culturists eventually need to “plant” the oysters in a natural environment, since the cost of cultivated algae as a food source soon becomes prohibitive. These seed oysters can be cultured on a prepared water bottom with shell or other suitable substrate, or conversely in intertidal zones in mesh bags secured with an anchored line. Intertidal culture tends to reduce problems with predators and fouling organisms.
An alternative culture method involves off-bottom grow-out of seed oysters in, or on, specialized structures. Off-bottom culture techniques include bags suspended from long-lines or vertical “racks,” strings of oyster shell or other suitable substrate hanging from racks, stakes with attached oyster shells, lantern nets hung grom floats, mesh tubes rotated by currents. All these off-bottom methods are designed to take advantage of the food and oxygen available in the entire water column, while reducing problems with predators and sediment accumulation. Under certain conditions, off-bottom culture can produce harvest-sized oysters in less than half the time required for on-bottom culture.
Generally, there are four main sectors in the oyster industry: harvesters, wholesalers, processors and retailers. Oyster harvesting includes wild and cultivated harvesting of mature oysters. Harvested oysters are generally delivered to wholesalers and processors; in some cases, they are directly delivered to restaurants or other retail outlets. The wholesalers may repack the shellstock into sacks, boxes or bushels and sell them to other wholesalers or to processors. They may also sell them to restaurants or other retail outlets. They are generally sold in dozens, by the bushel bag or in bushel-fraction boxes.
Oysters are harvested in a variety of methods. In areas where oyster reefs are exposed by low tide, they are hand picked. In shallow areas, tongs are used to harvest oysters. Tonging is one of the oldest method of harvesting, where tongs work like a pair of post-hole diggers with handles that are at least 10 feet long. Oysters are also harvested by dredging from oyster boats, using metal baskets with rows of spike-like teeth. Oysters are harvested throughout the year, but the meat yield differs with the season. Oysters harvested in the winter yield roughly eight pounds of oyster meat per sack while oysters harvested in the summer on average yield six pounds per sack.
In the United States, oysters are harvested from both leased and public waters. With the collapse of wild oyster harvests in the Chesapeake Bay around the turn of the century, leases were legalized to encourage revitalization of the industry. Today, what harvests are still available in the Chesapeake come largely from private leases.
Louisiana’s oyster industry is primarily a lease-based industry, where oysters are cultivated on both public seed grounds and privately leased state water bottoms. Oystermen lease water bottoms from the state (up to a maximum of 1,000 acres) and use that area for oyster culture. They typically dredge seed from public grounds and transport the seed to their lease, where the young oysters are allowed to grow for 1 to 2 years. The mature oysters are then harvested and packed into burlap sacks, which are tagged with information such as harvester name, date and location of harvest, before being marketed.
The processing sector buys shellstock oysters from wholesalers and other processors and, in some cases, they directly buy from harvesters. The oyster industry also involves vertical integration, where a fully integrated company may do everything from managing their own seed operation, through growing and harvesting, to shucking-sorting and delivering to wholesalers and retailers. Processing plants manually shuck shellstock oysters and place them in several different sizes and types of containers for sale to restaurants, retailers and other processors. Oysters for the halfshell market are sorted, graded and washed, and later placed in cardboard boxes and burlap sacks.
Processors typically sell oysters as fresh raw shucked, processed halfshell or as other value-added products such as smoked, cooked, canned and breaded oysters. Oysters generally reach consumers live in the shell, as fresh, frozen or canned product, or further processed such as frozen and breaded. Shucked oyster meats are graded and sold according to size in 8-ounce and 12-ounce cups, or in pint, quart or gallon containers.
Consumers perceive raw halfshell oysters based on characteristics including appearance (size, shape, color), odor, flavor (sweetness and saltiness) and texture (firmness). They prefer cup-shaped oysters where the meat fits the shell. Color is less important to consumers, but unpleasant odors are regarded as an indication of spoilage. Consumers prefer fresh oysters, with a mild, salty flavor and no off-flavor, very tender and not mushy. They generally consume cooked oysters at home and consume both raw and cooked oysters (steamed oysters or oysters Rockefeller) in restaurants.
Posadas and Posadas (2003) conducted a survey that indicated males consume more oyster meat than females. The survey also indicated that oysters are mainly consumed by people with education beyond the high school level. Major factors non-oyster consumers gave for not eating raw oysters was sliminess and appearance. Conversely, the major factor oyster consumers gave for eating raw oysters was flavor.
Exports and Imports
According to the Economic Research Service (ERS), 7.6 million pounds of U.S. oysters, up 20 percent from 2009, and valued at $22.2 million, up 14 percent, were exported in 2010. Canada was the major market for the oysters, followed by China and Taiwan (FAS 2010). The United States exports oyster seed, as well as live, fresh, frozen, dried, salted and brine forms of oyster.
The ERS also reported that more than 20.5 million pounds of oysters, up 16 percent from 2009, and valued at $55.7 million, up 17 percent, were imported in 2010. The chief suppliers were (in order): China, South Korea and Canada. The United States imports most of its canned and smoked as well as canned and brine oysters from China and South Korea, while most fresh or frozen oysters come from Canada. Canned oysters are the major form of U.S. imports. Oyster imports are expected to keep increasing due to shortages from hurricane damage in the Gulf Coast region and from continued diseases in the Chesapeake region.
All oyster dealers in the United States must be certified under the National Shellfish Sanitation Program (NSSP) to market oyster products in interstate commerce. Processing plants that ship oysters are certified as interstate or intrastate shippers. Interstate certified shippers may ship oysters across state lines, while intrastate certified shippers may ship oysters only within their state borders. Interstate shippers are inspected and certified by individual states, which later provide lists to the FDA. The FDA uses this information to publish the Interstate Certified Shellfish Shippers List. Intrastate shippers are also inspected and certified by individual states, but those states maintain their own lists. State agencies involved in certification include departments of health, marine resources, agriculture, natural resources and wildlife and fisheries (Muth et al. 2000).
The FDA’s NSSP carefully monitors oysters from their growing waters through processing plants and finally to retail outlets. The NSSP maintains a Manual of Operations, which is routinely revised by the Interstate Shellfish Sanitation Conference, a voluntary group composed of members from FDA, state health regulatory agencies and industry (Perkins 1995).
Emerging Developments and Outlook
Globally, many oyster fisheries continue to decline. Aquaculture practices are increasingly cited as the only practical means to sustain supplies. Innovations on the horizon include the use of genetically improved strains, off-bottom culture, and increased hatchery production of seedstock. Indeed, according to the National Marine Fisheries Service (NMFS), approximately 97 percent of global oyster landings in 2008 and 2009 were attributable to aquaculture. In contrast, aquaculture production of oysters in the U.S. only increased from 26.2 million pounds in 2004 to 32 million pounds in 2009 (NMFS). Oysters continue to increase in value, with reported price indexes (based on a 1982 value of 100) increasing from 205 in 2004 to 298 in 2010 according to the NMFS. The average U.S. ex-vessel price per pound of meats increased from $3.84 in 2009 to $4.19 in 2010. Opportunities exist in many areas to develop sustainable aquaculture practices for both native and introduced oyster species, although regulatory issues may constrain industry development in some locations. Other constraints involve the costs of constructing and operating hatcheries, conflicts with navigation in public waters, and the potential for catastrophic losses from pollution, red tides (and similar organisms), and diseases.
Annual Commercial Landing Statistics, Fisheries Statistics, National Marine Fisheries Service (NMFS).
Census of Aquaculture (2005), USDA, 2006.
Global Agricultural Trade System (GATS), Foreign Ag Service (FAS), USDA.
Import and Exports of Fishery Products 2011, Fisheries Statistics Division, NMFS, 2012.
Louisiana Summary: Agricultural and Natural Resources, Louisiana State University Agricultural Center, 2012.
Muth, K.M., D.W. Anderson, S.A. Karns, B.C. Murray, and J.L. Domanico, 2000, Economic Impacts of Requiring Post-Harvest Treatment of Oysters, Research Triangle Institute, North Carolina.
Oyster Market Report, Globefish, FAO, 2008.
Perkins, E.B, 1995, Aquacultured Oyster Products: Inspection, Quality, Handling, Storage, Safety, Southern Regional Aquaculture Center.
Posadas, C.B. and R.A. Posadas, Consumer Preferences For Postharvest Processed Raw Oysters In Coastal Mississippi, Mississippi State University, Mississippi Sea Grant Extension Program and Mississippi Department of Marine Resources.
Links checked: August 2013