Oysters and Lower Nanticoke Oyster Gardening

The Eastern oyster (Crassostrea virginica) is one of the Chesapeake Bay’s most well-known iconic species, economically, ecologically, and gastronomically! Oysters were once so abundant in the Chesapeake Bay that the reefs they created defined the major river channels in the Bay watershed. Scientists estimate that these native oysters were once able to filter the entire water volume in the Bay in less than one week! Today, it takes over a year for Chesapeake oysters to filter the same amount of water. Unfortunately, since the late 1800s the Chesapeake’s oyster population has declined drastically due to over-harvesting, disease, and habitat loss.

It’s not all bad news for oysters, however. The Nanticoke Watershed Alliance has partnered with the Oyster Recovery Partnership and local residents to restore the oyster population in the Nanticoke. The ORP assists their partners in designing and implementing oyster restoration projects that maximize ecosystem services that oysters can provide. They also provide spat-on-shell and cages to participants. ORP is involved in several different types of projects to achieve their goal including, planting oysters in sanctuaries, manage reserves, and public fishing grounds. Since 1998, they have planted 8 billion oysters over 2,460 acres of Maryland waters.

Oysters flourish in year-long brackish water and can’t survive in freshwater areas, so oyster gardening is limited to the lower Nanticoke (roughly, Tyaskin south). If you’re interested in joining the Lower Nanticoke Oyster Gardening team, contact Beth Wasden.

Also, the Nanticoke River is fortunate to have a high number of bottom acreage leased, an older-school version of aquaculture that allows oyster farmers to grow, tend, and harvest oysters without the muss and fuss of cages or floats.

Oyster Appearance, Habitat, and Range

Eastern oysters are bivalves, meaning they are composed of two shells. The two shells enclose to protect the oyster’s soft body. On average, an adult an oyster can grow three to five inches in length, but can grow up to eight inches in length. Oysters are sessile (fixed in one place) and need a hard surface to attach to, they are commonly clustered together forming an oyster bar, bed, or reef.

 

An oyster bar exposed at low tide in the Chesapeake Bay.

 

The Eastern oyster can be found throughout the middle and lower Chesapeake Bay and its rivers. Their range extends along the Eastern Seaboard of North America from the Gulf of St. Lawrence to the Gulf of Mexico. Oysters live in brackish and salt water environments and can commonly be found in shallow saltwater bays and estuaries, in water 2 to 26 feet deep in the Chesapeake Bay.

Adult oysters can tolerate salinity levels between 8 and 40 ppt (parts per thousand) but salinity levels between 14 and 28 ppt is ideal. The Chesapeake Bay watershed from July 2018 through June 2019 received 60 to 80 inches of rain. That is roughly 110% to 150% more rainfall than average. The ground was unable to soak up all the excess rainfall and freshwater began to flow into the Bay’s tributaries, eventually making its way to the Bay. The freshwater severely diluted the brackish bay water. This has negatively impacted the ability of oysters to produce spat (offspring). ORP works with UMD and Horn Point Hatchery and because of the low salinity in the Chesapeake Bay, the hatchery was unable to produce the amount of oyster spat that it would in a normal year. If you would like to read more on this topic, check out this Baltimore Sun article.

Ecosystem Services

Oysters are filter-feeders. That means they acquire food by pumping water through their gills, which trap particles of food as well as nutrients, sediments, and chemical contaminants suspended in the water. Filter-feeders help keep the water clean and clear for submerged aquatic vegetation and aquatic critters. Depending on the water quality, an oyster can filter up to 50 gallons in 24 hours. The reefs oysters form also play an important role in the Bay’s ecosystem. Oyster reefs:

  • Provide habitat for juvenile fish and invertebrates. The structure that oyster reefs create provide crevices for fish and crabs to hide from predators.
  • Act as feeding grounds for wading birds and economically-important game fish.
  • Stabilize shorelines and reduce erosion. Oyster reefs protect underwater vegetation and waterfront communities from waves, floods, and tides. Healthy reefs serve as valuable habitat. Also, they reduce wave energy, which prevents erosion, and help protect wetlands.

Threats

Oyster reefs are far less abundant today than they once were. Due to decades of damage from over-harvesting, an increase in diseases, and decreases in the levels of salinity in some years, such as 2018-2019, the Bay’s oyster population is less than 1% of what it was in the past. Runoff and erosion from industry, farming, and development feed algal blooms, create low or no-dissolved oxygen zones, and smother oysters with soil and other material.

 

 

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