Once, oysters grew upon great bars, or reefs, which lined the shores of our local estuaries. These bars began with an initial colonization of a suitable habitat, then grew, generation upon generation, to form great reefs. Early English settlers marvelled at the extent of these reefs, and were careful to point them out on nautical charts, so that unfamiliar travellers would not wreck their ships on these huge structures. Through the centuries these reefs have been mined away in our eagerness to harvest the delectable oysters. Today, despite legal protection, there are virtually no naturally occurring oyster reefs in the Chesapeake Bay.
Oysters settle as spat onto shells or other hard surfaces.
With no reefs present, the spat must settle on bottom substrates where they are much more susceptible to the siltation, and other stresses, which inhibit growth and increase the susceptibility to disease.