Chesapeake Bay Oysters
oyster float for raising oysters at your dock.
The following information is from the Tidewater Oyster Gardeners Association.
OYSTER GARDENING IN VIRGINIA
As a result of disease, pollution and overharvesting, the Virginia oyster harvest in the Chesapeake Bay has declined over many years, from nearly ten million bushels at the turn of the century to a few tens of thousands in the 1990s.
To improve the oyster population in the Bay, the Virginia Institute of Marine Science (VIMS) has encouraged the use of aquaculture methods to increase the growth rate of native oysters. By placing the animals in a favorable growing environment, maturity can be reached in 18 to 24 months, instead of the 4 or 5 years required in natural bottom growth. Because the parasitic diseases MSX and Dermo usually take two years to kill an oyster, the aquaculture method makes successful harvest more likely.
Aquaculture methods of oyster culture have been in use for about a decade. Some of these original growing operations are now becoming profitable and have expanded into commercial ventures. About three years ago, VIMS encouraged a group of amateur growers to join the project, a group which has grown to more than 200 participants. These "oyster gardeners" typically start about 2000 oyster seed per year.
Oyster gardeners have generally three goals:
1. Experiment with the aquaculture method in the hope of improving its efficiency.
2. Get a lot of oysters in the water to provide filtering of the Bay.
3. Harvest the crop before the diseases hit it and enjoy an oyster roast!
As disease-resistant oysters are developed by VIMS, oyster gardeners will be encouraged to grow and support a number of animals permanently. The large number of gardening sites will help distribute the resistant oysters over the bay, where they may spawn and multiply.
The principle of oyster aquaculture is really very simple: get the baby animals into an environment where they have enough room to feed, are protected from smothering by silt, are fed by flowing water of moderate salinity, and can't be reached by predators.
Oyster gardening starts with seed oysters which are 1/4 to 1/2 inch in length. They are easily handled in mesh bags. Oyster seed is produced in nurseries where selected brood stock is allowed to spawn under ideal conditions. The microscopic animals "set" by attaching to crushed gravel or broken shell where they begin to grow. The nursery devotes about two months to developing the seeds to the size for gardening; typically, seeds are distributed to gardeners in September or October.
The seeds grow rapidly in fall and spring, and although they will encounter the diseases that summer, they have two more rapid growing seasons before the disease is fatal. Thus, the young oysters will reach harvest size by 12 to 14 months, and can be harvested through the winter and the following spring.
Various types of floating devices have been used successfully. The floats hold animals a few inches below the surface of the water. Baskets generally are made of plastic or metal mesh with openings large enough to let the water and food flow through, while small enough to keep the oysters in, and are buoyed up by PVC pipe frames, or in some cases, bottles. The floats must be cleaned occasionally because algae and other creatures also find the environment attractive and clog the openings of the mesh. When the oysters are out of the original growing bags they must be protected from otters, raccoons, and other predators. Various materials can be used to fashion a lid to exclude predators.
VIMS and other labs have been working for several years on cross-breeding specimens of Chesapeake Bay oysters that have shown resistance to MSX and Dermo. The latest generation of these experiments shows a good growth rate. Seeds from this cross-breeding may be available in the near future, and will be distributed as soon as possible to growers.
Currently several groups of oyster gardeners are working to encourage residents of local coastal waters to expand oyster aquaculture. In addition, the Virginia Shellfish Growers Association (VSGA) supports both commercial and non-commercial growers of clams and oysters.
Oyster gardener groups provide newsletters and workshops as well as coordinating the ordering and distribution of seed each year. VSGA maintains a newsletter and is active in matters related to legislation and aquaculture development.
SHELLFISH HEALTH CONSIDERATIONS
Water that has been found to contain excessive E. coli bacteria levels is condemned by the Division of Shellfish Sanitation of the Virginia Department of Health. Condemnation means that oysters cannot be eaten directly from those waters. Records of the condition of the waters in the Northern Neck and Middle Peninsula are kept at the office in White Stone and south of the York at the Norfolk office.
Condemned waters do not hinder the growth and spawning of the oysters, and oysters that have grown in condemned water can be rendered safe by moving them to clean water for a period of time when the water is above 50 degrees F. Most growers with this problem usually move a supply of mature animals to a friend's dock early enough so that they are available for harvest when desired.
For more help, and useful links, try visiting the website for the Tidewater Oyster Gardening Association.
For more details, feel
free to call:
Bruce & Jill Anderson
Copyright 2002, Bruce & Jill Anderson