Aquaculture is Agriculture 

Traditional harvest relied on healthy reef systems of built up oyster shell bottoms. These reef systems would recruit new oysters to grow. Oystermen used tongs that averaged 12ft long to feel out the bottom and bring up whatever they could find. They would sort the shell and the small oysters and throw that back to the bottom. This is hard work and still done in some areas. 

Baskets are fill with baby oysters. The babies are tumbled, culled and sorted. The intensive part comes in that they need to be checked regularly.  The return is higher because you are not feeling around on the bottom hoping to get sized (3") oysters. The farmer now can grow where historically oysters could not grow or have disappeared. Oyster aquaculture started in New England and is appearing all over the world.