It is often assumed that oysters were not cultivated before the 11th century. Fishermen were just taking abundant oysters from the wild and moving on to new reefs as they exhausted one site. This may or may not be true. The Romans could have shown them how, if needed be, and the presumption smacks of city patrimony.
The very nature of these estuaries also discredits the idea. The largest and most famous native English oyster beds are around the mouth of the Thames, along the north Kent coast around Whitstable and Faversham and across the water in creeks at Colne, Crouch, Maldon, Blackwater and Roach along the coast of Essex.
But Essex was rarely self sufficient in oysters, or never had enough to meet demand. Its tidal creeks opened on to the Thames which would wash away the spat. Except at Paglesham on the Roach where the twin tides around Foulness Island keep the spat inland and made it the natural hatchery. But the other creeks would take in oysters from Kent and further afield to fatten them off for market. Quite when this started is not clear, but it was certainly ancient and logical and not always amicable.
These towns enjoyed two advantages over other fisheries. Billingsgate market for London was up river via the Thames, which may be why the East Anglian creeks, being that much further north, which although they could be used for raising oysters, and still are at Orford, were often turned over to mussels instead which were thought to be an easier sale. But these harbours were also a front door for the French and Dutch boats to trade and smuggle unseen. And a backdrop to an invisible international royal politic.
