Seafood such as oysters, mussels and crayfish are not uncommon. These are primarily associated with bivalve molluscs, such as mussels, clams, oysters and scallops. The class has 30,000 species, including scallops, clams, oysters and mussels. Singaporeans also enjoy a wide variety of seafood including crabs, clams, squid, and oysters. Other commonly eaten molluscs include octopuses and squids, whelks, oysters, and scallops. Crab, lobster, shrimp, jellyfish, oysters and catfish are the basis of the marine fishery. The Chesapeake Bay is host to many species, including blue crabs, clams, oysters, and rockfish. Oyster depuration begins after the harvest of oysters from farmed locations. They fished the Hudson River for shad, oysters and other shellfish. Oyster sauce describes a number of sauces made by cooking oysters. Ropes can be hung in water to grow algae, oysters and mussels. This feast customarily includes special dishes including foie gras, seafood such as oysters, and champagne. The parish exports millions of pounds of shrimp, crab, oysters, and fish annually. Some dead oysters, or oyster shells which are full of sand, may be closed. There are references in sources to canned cheese, fruit, meat, oysters, and sardines.