In Chesapeake Bay, vast stretches of prolific oyster grounds supported a large public fishery until the late 19th century, reducing the interest in developing aquaculture techniques. In 1884, 615,000 tons of oysters were produced in Chesapeake Bay, around 20% of the current worldwide production (Goulletquer et al., 1994a). Maryland and Virginia adopted various approaches and priorities when landings began to decrease. In the 1870s, Virginia oystermen established a system where they harvested seed from public grounds and transferred it to their leases to grow to market size. This may be considered a rudimentary oyster culture system, reliant on natural spatfall originating in public beds but based on private-sector initiative and investment. In Maryland waters only a small portion of the bottom is available for leasing, a total of 11,000 acres in 1892 and 12,000 acres in 1952 (MacKenzie, 1997). From the 1920s to the 1950s, annual harvests from leased grounds were about 100,000 bushels, an insignificant amount when compared to landings from public fisheries (F. Sieling, Maryland Department of Natural Resources, Annapolis, personal communication, 1994). In 1960, the state of Maryland started a repletion program based on shell deployment to maximize recruitment and support the oyster fishery (MacKenzie, 1997). Although this may also be considered a foray into oyster husbandry, it is based on the public fishery rather than the private efforts undertaken in Virginia. Most of the seed supplying both Virginia and Maryland has originated from public beds (e.g., James River). Most leaseholders on Virginia’s Eastern Shore collected their own seed by spreading shell material in parallel rows on intertidal grounds and transplanting the seeded shell on tidal leases (Haven, 1972). Oyster culture in the Chesapeake Bay has been a technologically unsophisticated practice, relying mainly on natural spatfall in public beds and using extensive on-bottom culture. Aquaculture methods have not been employed to any appreciable extent in the Chesapeake Bay, not even methods to maximize spat recruitment using artificial spat collectors.
Worldwide aquaculture practices for shellfish have been highly variable, depending on a range of internal and external constraints. The wide variety of options for culture practices reflects the physiological flexibility of oysters, such as tolerance of low oxygen conditions, relatively high turbidity, and various salinity and temperature regimes. Oysters filter feed on microscopic algae that are typically abundant in coastal waters. Because oysters do not need additional food to sustain growth, this species is relatively inexpensive and easy to culture. In some productive