Some form of cutlivation of the Eastern (or American) Oyster has been going on for 150 years on Cape Cod, especially in Wellfleet. At first, this just consisted of importing wild oysters from elsewhere in their Atlantic or Gulf coast range, and giving them a while to absorb that special Wellfleet flavor.
There is no way that one small harbor could support the nationwide demand for naturally-produced Wellfleet Oysters.
As we sat on the deck watched the oystermen at work on their cages at low tide, we wondered where they buy the baby oysters.
I found out how the whole system works (link has great photos). The laboratory-bred spat from the hatcheries are bought by nurseries, then they are sold to the watermen who do the "grow-out" of the seed oysters. It is quite remarkable. No wonder they aren't cheap.
Photo on top: large scale commercial oyster grow-out in the southern US
Photo on bottom: oystermen tending their oyster cages in Wellfleet at low tide. Production is limited by town regulations, so there is no industrial-scale production and all are beach-bottom cultured instead of being grown on rafts, slowing their growth but making them tastier.