Species Spotlight: Eastern Oyster
In this week’s species spotlight let’s take a look at a species that the CCE Marine team works very closely with - the eastern oyster!
Oysters belong to the Mollusca phylum. Along with their cousins, clams, scallops, and mussels, oysters are classified as bivalves, meaning “two shells”. These hard shells are made of calcium carbonate.
Centuries ago, oysters were plentiful in New York waters. Due to disease, over-harvesting, habitat loss, and poor water quality, the populations crashed over time. Now, thanks to regulations like the Clean Water Act of 1970, NY waters can support oyster populations once again!
Oyster aquaculture is a growing industry in efforts to produce oysters for human consumption and to help restore natural populations. Cornell Cooperative Extension Marine Program operates a hatchery in Southold and partners with many other town hatcheries and local oyster growers to produce millions of shellfish. CCE’s mission is restoration, so when oysters are large enough they can be released into bays to repopulate or even built into oyster reefs!
Eastern Oyster
Crassostrea virginica
The CCE Marine Team getting ready to deploy spat-on-shell oysters!
Those tiny “dots” are each baby oysters, or spat, attached to recycled shell!
An adult oyster can filter up to 50 gallons a day!
The start of an oyster reef!
Eastern Oyster
Scientific Name: Crassostrea virginica
Identification: Eastern oysters grow to three to five inches in length, but can reach eight inches in length at maturity. The oyster’s soft body is enclosed between two rough oval shaped shells. These shells often have a “cupped” shape to them. The outer shells vary in color from white to gray to tan. The inside of the shell is white to off/white to brownish in color with a purple muscle scar on the inside.
Diet: Oysters are filter feeders. They feed on microalgae, or phytoplankton, in the water around them. They do this by creating a current, taking in water through a siphon, filtering the algae with their gills, and expelling clean water through a second siphon.
Habitat: Eastern oysters live in brackish and salty waters and can be found from 8–35 feet deep. They can inhabit both intertidal and subtidal zones. They attach to firm bottom areas and to each other to form oyster reefs. Eastern oysters are found along eastern North America from the Gulf of St. Lawrence to the Gulf of Mexico. They can also be found in the Chesapeake Bay and its rivers.
Find this Species: Try looking for eastern oysters on top of the seafloor in shallow waters! Also take a look on rocks, docks, clusters of old shells, or any hard-submerged surface in salty or brackish waters! Where you find one you will usually find a cluster!
Interesting Facts: Oysters are born as swimming larvae, then unlike their other bivalve cousins, they settle on a hard surface becoming spat! Once settled, oysters never move again!
When oysters feed, they are helping to clean the surrounding water! Adult oysters can filter up to 50 gallons of seawater a day!
Oysters provide a key structural element within their ecosystem. They serve as ecosystem engineers and create oyster reefs! Oyster reefs, like coral reefs, provide key habitat for a variety of different species of fish, invertebrates, and macrofauna! They also can protect shorelines from erosion!
Eastern oysters have fast growing rates and high reproduction rates. They mature as males first, then develop female reproductive capabilities later in life. A female oyster can produce over 100 million eggs during a spawning event!
Some of the threats to eastern oysters include: habitat loss, overharvesting, disease, degraded water quality, and changing conditions due to climate change.