Pacific Oysters are cultivated on the west coasts of the United States and Canada, as well as in Japan, South Korea, and China. The Pacific Coast Shellfish Growers Association (PCSGA 2000) reports production of 42,140 mt of oysters in Washington, Oregon, Alaska and California. The vast majority of these are Pacific Oysters. About 82% of oyster production was in Washington, 11% in California, 6% in Oregon and less than 1% in Alaska.

NMFS does not report imports of oysters at the species level. Imports of "oysters" come from China (817 mt), South Korea (358 mt), Canada (119 mt), and lesser amounts from New Zealand and Japan. These nations are producing mostly Pacific Oysters. The extent to which the NMFS data include farm-raised oysters is unclear.

All oyster farms on the west coast use a combination of on-bottom and suspension methods to farm oysters. On bottom culture is currently the most common method for farming Pacific Oysters in the U.S. The suspension cultures may be longline or racks (Downery, pers. comm. 2004).

In Asia, most of the Pacific Oysters are raised in suspension culture systems. Japanese growers generally use 10m x 20m rafts that are constructed from bamboo. In China, racks are the most common suspension system. There is some bottom culture in China, in which cement bars are used to collect spat and grow out oysters. However, bottom culture does not contribute a significant portion of the oysters from China (Matthiessen 2001).

Although a variety of methods are used to culture Pacific Oysters, most of the Pacific Oysters in the U.S. market were raised in bottom cultures, so we award a score of 2 for this criterion.

There are serious issues with high stocking densities in South Korea, Japan, and presumably China. For example, in the Hiroshima Bay, Japan, intensive cultivation of Pacific Oysters has caused oxygen levels to decrease to harmful levels, leading to increased mortality (Matthiessen 2001). However, only a small amount of the oysters available in the U.S. are coming from China, so we do not subtract for this criterion.

Washington, Oregon, California, Alaska and British Columbia all have licensing controls for leasing land from the state/province. In Washington, most tidelands are privately owned, but aquatic farms must be registered through the Washington Department of Fish and Wildlife. All states’ shellfish farms are certified through a registered Shellfish Authority, which is usually the state's department of health or agriculture. Depending upon culture operations, shellfish farms may require various shoreline development or use permits through local county ordinances. Most shellfish aquaculture activities are permitted through the Army Corps of Engineers Nationwide Permit 4 (Downey 2004). It is unclear what the permitting practices are in South Korea, Japan and China, so we neither add nor subtract points for this factor.

No feed is used to farm Pacific Oysters, as they are filter-feeders, and get their nutrients from algae and other plankton in the water column (Matthiessen 2001).

No feed is used (Matthiessen 2001).

No feed is used (Matthiessen 2001).

No feed is used (Matthiessen 2001).

Treatment of effluent is not necessary because supplemental feed is not used to farm Pacific Oysters (Matthiessen 2001).

Chemicals are not generally used on oysters, however some may be used on oyster beds. For example, oyster farmers in Willapa Bay and Grays Harbor in Washington state may apply the pesticide Sevin (Carbaryl) to control burrowing shrimp. This practice is highly contentious as other organisms may be harmed (Johnson 2001). The use of Sevin is being phased out, and its use will be extinguished by 2012. As of yet, there are no feasible alternatives for farmers to control populations of the devastating burrowing shrimp.

Another chemical, "Habitat," is used to control the invasive Spartina plant, which has been turning tidelands into Spartina meadowlands. The use of Habitat has been supported by the Audubon Society and other conservation groups.

Practices in South Korea, China, and Japan are uncertain.

Although very dense farms in China have been shown to deplete oxygen from the water, most Pacific Oysters in the U.S. come from the west coast, where farmers will lower density to allow maximum growth rates. Generally, oysters improve water quality by filtering out algae and other plankton, thereby reducing levels of nitrogen, phosphorous and other nutrients (Downey, pers. comm., 2004).

In general, no controls are necessary for effluent from Pacific oyster operations, as the oysters are biofilters and contribute to the control of excess nutrients in the water column. However, in the U.S. water quality is monitored by the National Shellfish Sanitation Program, and in the event of contamination from harmful algal blooms (such as red tides) or bacteria, growing areas are closed to harvest to protect public health (Downey, pers. comm., 2004).

In Washington State, where Sevin may be applied on oyster beds, its application is highly regulated and monitored by the Washington Department of Ecology (Johnson, 2001).

Farming this species does not create waste.

Pacific Oysters are native to the western Pacific Ocean. They have been introduced and are well established in North America and many other areas of the world. While they are farmed in areas where they are non-native, such as the U.S. Pacific Northwest, oyster farming often aids in restoring the ecosystem functions of local oyster populations, which have often been depleted by disease and overharvesting (Matthiessen 2001; Conte 1996).

Pacific Oysters are farmed in the open water, so "escape" is common. This species is now well established in areas where it is not non-native, indicating that it does in fact survive in the surrounding ecosystem.

Olympia Oysters (Ostrea lurida) are the native oyster species in the Pacific Northwest, where Pacific Oysters are now farmed. In the mid to late 1800s, Olympia Oysters populations were decimated from overfishing and pollution. Farmers began to seed Pacific Oysters, and they quickly became the dominant oyster species in the region (Downey 2004; Matthiessen 2001). While Olympia Oyster populations remain below historical levels, their depletion was not a result of the introduction of the Pacific Oyster. In fact, restoration efforts for the Olympia Oyster are successful (Peabody, pers. comm., 2004), indicating that the presence of established Pacific Oyster populations is not inhibiting Olympia Oysters.

Although Pacific Oysters are not farmed on the East Coast, people have tried seeding them there in the past. Some scientiest believe that Pacific Oysters were the carrier of the MSX disease that has devastated American Oyster populations on the U.S. East Coast. However, this remains speculation, and has not been proved. Therefore, we do not subtract points for this factor. Additionally, disease outbreaks of Pacific Oysters are well contained. One disease called Denman Disease does not effect other shellfish, and is considered a much bigger problem within wild populations than on farms (Downey, pers. comm. 2004).

Several agencies are addressing the risk of escape and disease. Each state in the U.S. has a department of health or agriculture to oversee the transfer of shellfish between states under The National Shellfish Sanitation Program (NSSP) (Kraeuter and Castagna 2001). Agencies responsible for natural resource management (e.g., Washington Department of Fish and Game) oversee the transfer of live animals intended for replanting (such as planting out seed from hatcheries to growing areas). Also, a health program (called the "High Health Program"), developed by the Pacific Shellfish Institute, provides stringent guidelines for hatcheries to assure disease-free seed is supplied to industry for grow-out. This program was adopted by USDA Animal Health Inspection Program, and has become a national model (Downey, pers. comm., 2004).

Pacific oysters are generally grown in bays, inlets, and sounds, off-bottom, where they are afforded some degree of protection from waves and storm damage (Matthiessen 2001).

Like other bivalves, oysters enhance habitat function by improving water quality. Oysters filter out algae and other plankton, reducing levels of nitrogen, phosphorous and other nutrients (Downey, pers. comm., 2004). Pacific Oyster farms have encouraged the reestablishment of import eelgrass habitat, thereby enhancing habitat structure that is important for a range of species (Downey, pers. comm. 2004).

Burrowing shrimps, Mud and Ghost Shrimps, have devastated areas that were previously oyster farms. Once these shrimp colonize an area, most other biota is eradicated, and the area is no longer suitable for aquaculture. To date, no methods have been found to be effective at removing these shrimps (Downey, pers. comm., 2004). Farms for Pacific Oysters are therefore only created in areas where these shrimp have not yet colonized (Peabody, pers. comm., 2004). Oyster drills are currently kept under control by manually removing them, and by prohibiting the transfer of anything from areas where oyster drills have been identified (Downey, pers. comm. 2004).

From the 1920s to the 1970s, seed was imported from Japan, where operations are entirely dependent on wild populations for seed. Since then, almost all of the seed used in U.S. production has been hatchery-raised (Matthiessen 2001). Some scientists are concerned that the collection of wild seed in Japan could be harming wild populations, which are already suffering from coastal development (Matthiessen 2001). However, the U.S. market is not comprised of a significant amount of Japanese imports.

We add points here because most of the most of the Pacific Oysters in the U.S. market originated from hatchery-raised seed.