Generally, a shellfish farmer buys or collects juvenile shellfish, called "spat." He then puts them in special nets or lines (oysters and mussels) that are anchored in the ocean, or plants them on a beach (clams). The animals feed by filtering the abundant, high-quality plankton that naturally occur in the water. The farmer must keep the animals clean from algae and protect them from predators. He then harvests the animals when they grow to a marketable size.