Oysters are mollusks – shelled invertebrates (animals without backbones) in the same zoological phylum, Mollusca, as the mussel, clam, snail, octopus and squid. Oysters are also classified as bivalves. Their shells are in two parts, or "valves", held together by an elastic ligament hinge. An oyster makes its own shell, secreting calcium and other materials from glandular tissue in its soft flesh. Worldwide, there are more than 100 living oyster species. Several of these are particularly well suited for culturing in Washington State.
Oysters have gills for breathing. As water is drawn across the gills, these feathery organs also collect particles of food from the water. For protection, oysters clamp their two-part shells tightly together, using powerful muscles to hold tight. When sealed, an oyster can retain enough moisture to survive for hours, or if necessary, several days out of water.
Oysters are filter feeders and as such they filter their food out of the water column. The food consists mainly of dense blooms of phytoplankton or microalgae (single celled plants) that are naturally produced. In coastal estuaries, where Coast Seafoods Company grows its oysters, the microalgae blooms are generated in the off shore oceanic environment where upwelling of deep, nutrient rich water provides nutrients necessary for plant growth. Phytoplankton blooms are continually replenished inside the estuaries through the daily exchange of tidal waters. This process of off shore phytoplankton blooms and daily exchange of seawater over oyster grow-out grounds is a completely natural process.
In the states of Washington and California, the water quality in coastal estuaries is continually monitored for harmful algae blooms and pollutants. Should harmful algal blooms develop or a pollution event occur, the oyster beds are closed to harvest until tests reveal the oysters are pollution free and safe to eat. These two states have the highest water quality standards in the country, helping to ensure that our oysters are grown in a pollution free, clean environment.