Choosing a Location
The “ecosystem services” provided by shellfish play a critical role in the health of coastal water bodies. In the estuaries most impacted, such as the Chesapeake Bay, the environmental community has placed emphasis on increasing shellfish populations, including the encouragement of oyster gardening.
The most important factors to consider when selecting a location to set up an oyster garden:
• Salinity and temperature,
• Phytoplankton abundance and types,
• Sediment types,
• Water depth,
• Protection from severe storms, winter ice and boat wakes,
• Presence of disease organisms or harmful phytoplankton blooms,
• Water quality acceptable for harvest of oysters for human consumption,
Oyster growth rates are dependent upon salinity. Salinity is measured in grams of salt per litre of water, or parts per thousand (ppt or ‰). Oysters require a salinity of at least 8 ppt to grow and oyster growth increases with increased salinity. Anything below 10 ppt salinities and the oyster growth rates are generally reduced. Optimal salinity is between 10 to 20+ ppt with the highest growth rates at higher salinities.
Testing water salinity can be done with a hydrometer. Hydrometers may be found easily at Amazon.
For two reasons your site must have a minimum water depth of one foot, even at the lowest tide:
- Oysters can only filter water and grow when they are submerged
- In the winter, when tides and winds may cause your oysters to be exposed at low tide, your oysters may freeze. Oysters can be frozen solid in the water and survive, but they will die if exposed to sub freezing air temperatures.
Oysters need dissolved oxygen levels in the water of at least 3.2 milligrams per litre, but 5.5 mg/l or more is best for survival and growth. Colder water can hold more oxygen than warmer water.
The quantity and quality of food available to oysters can vary considerably from location to location. The quantity and quality are a function of the hydrodynamics at a site (how the water is moving through the site) as well as the abundance of phytoplankton in the water. You may have to evaluate different seed stocks and handling strategies in order to maximize oyster growth and survival.