Every other farm animal eats something a farmer has to buy. An oyster eats whatever the tide brings in — and leaves the water clearer than it found it.
Oysters are filter feeders. NOAA puts it plainly: growing them requires no feed — they strain tiny drifting plants straight out of the water. Once past the hatchery stage, nobody feeds them again.
Basis: NOAA Fisheries, farmed Eastern oyster: “Growing oysters requires no feed—they filter phytoplankton directly from the water column”; “Once past the larval stage in the hatchery, oysters do not need to be fed because they filter their food from the water column.”
One grown Pacific oyster can push up to 50 gallons of seawater through itself in a single day — and what comes out is clearer than what went in, which lets more sunlight reach the plants growing underwater.
Basis: NOAA Fisheries, Pacific oyster: “They are filter feeders, cleaning the water as they eat—an adult Pacific oyster can filter up to 50 gallons of seawater per day. This filtering of the water improves light penetration for submerged aquatic vegetation to thrive.”
Because dinner arrives by water, an oyster farm is a patch of tidal sea, not a field. NOAA describes oysters grown straight on the beach bottom, or in mesh bags, trays and cages — and in some places the whole farm is left out of the water for a while at every low tide.
Basis: NOAA Fisheries: “Oysters are grown in tidal areas. They can be grown directly on the beach bottom or in mesh bags, trays, or cages that are either anchored in the water column or floated on rafts”; “In some places, oysters are farmed intertidally and live out of the water for a time at low tide.”
The oyster that leads West Coast farming is a traveller. The Pacific oyster was introduced from Japan in the 1920s by the Washington State Department of Fisheries — its other names are still Japanese oyster and Miyagi oyster. It is not native to the United States, and in places such as Puget Sound it now lives here on its own.
Basis: NOAA Fisheries, Pacific oyster: “The Pacific oyster, introduced from Japan in the 1920’s by the Washington State Department of Fisheries, is now a popular West Coast aquaculture species”; “Also Known As Japanese oyster, Miyagi oyster, Pacific cupped oyster”; “Although Pacific oysters are not native to the United States, they have become naturalized in some areas of Washington state including Puget Sound.”
On the other coast, the native Eastern oyster tells a harder story. Its reefs were once so big that ships had to steer around them; in the Chesapeake Bay, scientists now estimate the population at 1 to 2 percent of historic levels, and NOAA and its partners are rebuilding reefs on purpose.
Basis: NOAA Fisheries, Eastern oyster: “In some places, reefs were so big that ships had to navigate around them”; “In the Chesapeake Bay, scientists estimate that the population is only at 1 to 2 percent of historic levels”; “NOAA is teaming up with other organizations to restore oyster reefs up and down the East Coast”; “In the Chesapeake Bay, we are part of the world’s largest oyster restoration effort.”
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