Since 2008 the Marine Discovery Center has been awarded grants to perform shoreline restoration work at various sites in our local estuary. Much of this work includes oyster restoration. Our local oyster species, Crassotrea virginica or the Easter Oyster, are threatened by various forces such as incumbent waves from boat wake, adverse weather (particularly strong winds), and seasonally extreme tides. Oyster beds are highly important to the health of our estuary. They possess the ability to dissipate wave energy, which reduces water’s erosive forces on land masses. Oysters are filter feeders, and one oyster has the amazing ability to filter up to 60 gallons of water in 24 hours. Healthy oyster beds throughout our rivers have the potential to improve overall water quality by removing much of the particulate material suspended in the water column. In addition, oyster beds serve as habitat and breeding grounds for numerous species of finfish, and are an important part of the food chain.
We use two methodologies for oyster restoration; oyster mats and oyster bags. Oyster mats consist of 36 individual oyster shells attached to one side of a 16”x 16” piece of UV-resistant plastic mesh. After the desired number of mats are constructed (usually several hundered), they are laid down in a grid pattern over the restoration area. The mats are secured together and weighed down by placing and cable-tying concrete sprinkler “donuts” at the corners and edges of the mats. Once spawning season commences, the existing living oysters in the lagoon release their gametes into the water. The larval oysters floating around in the water column are attracted to the chemical signal given off by the shells on our mats, where the larvae settle and begin to grow a new living reef on the structure. It is advantageous for the larvae to settle on other oyster beds or shells because the interstices of the reef helps protect them from predators, and the cumulative weight of the new oyster growth helps build and strengthen the reef as well. Oyster bags are made of a hollow mesh tube filled with loose oyster shell. The mesh tubes are typically between 3 and 4 ft. long. Each oyster bag contains about one 5 gallon bucket of oyster shells. They essentially look like a large sand bag, but with a fine 1” mesh. The mesh holds the loose shell together but allows for recruitment of growth through the holes in the material, as the bags recruit growth in the same way as the mats. The bags can be stacked on top of each other, arranged in a linear fashion, or any type of configuration desired. Both have been proven to be effective methods for restoring oyster populations.
Here is the reference for a good article on oyster restoration:
Author(s): LISA M. WALL, LINDA J. WALTERS, RAYMOND E. GRIZZLE, and PAUL E. SACKS
Source: Journal of Shellfish Research, 24(4):965-973. 2005.
Published By: National Shellfisheries Association