Shellfish Gardening
in Washington State

 

  Growing Oysters and Clams
 

How do I get started?

The following resources on the web have a wealth of information about how to start your Shellfish Garden:

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Do I need a permit to grow oysters for my own use and consumption?

You may need to get a permit to seed your tidelands and grow shellfish. This will depend on your specific location and the growing methods you chose. You should contact both:

The following  activities will also probably require a permit from one or more agencies:

A good place to start to find out if you need a permit is the Puget Sound Shorelines permits and regulations page.  Another more in-depth resource is the Pacific Coast Shellfish Grower Association Government Pages.

The following state agencies regulate shellfish culture:

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What types of clams and oysters can I grow?

Sea Grant Washington's Oyster Stew gives you examples of the oyster varieties you can typically grow in the northwest region of Washington state. However, once you get out to your tidelands you might find other shellfish already growing there. Luckily the Washington Department of Fish and Wildlife has a useful shellfish identification guide.

Manila Clams are the variety most often available as seed. As with oysters, you will find native clams on your tidelands, and some are edible. Both the Department of Fish and Wildlife and King County have good clam identification guides.

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What are "triploid" oysters?

"Diploid" oysters reproduce naturally in warmer water. During their reproduction cycle diploid oysters become soft and milky, and are usually not at their best stage for eating raw.

"Triploid" oysters are infertile and do not reproduce in the summer months. Triploid oysters conserve their glycogen content during the summer and remain firm full and sweet in their raw state.

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Water Quality Issues - Can I eat the shellfish that I grow?

Shellfish are filter feeders and eat microscopic plants (phytoplankton) that are floating in the surrounding water. Shellfish capture their food by filtering large volumes of water. If harmful bacteria or marine biotoxins are also present in the water, the shellfish will have the potential to consume them also. This can make the shellfish unsafe for human consumption.

The Washington State Department of Health certifies the growing waters of commercial culture operations to assure they are safe and uncontaminated by pollution sources. They also test commercially produced shellfish to assure it is free of any marine biotoxins. Some recreational beaches are also certified by the Washington State Department of Health.

The beach you are planting may not have the same level of protection that commercial and public beds have. Before consuming your shellfish, you should contact the State Department of Health to determine if your shellfish are healthy to eat.

Cooking the shellfish will destroy harmful bacteria associated with pollution sources but it will not destroy biotoxins. For this reason it is important to call the PSP Hotline at (800) 562-5632 or check the Marine Biotoxin Bulletin before harvesting to assure your beach is not under a red tide closure.

Closures due to water pollution: 

The State Department of Health (DOH) conducts detailed surveys to classify commercial shellfish growing areas. If your growing area is close to a classified area, the growing conditions and safety of shellfish grown in the classified area may apply to you. The DOH website has additional information about area classifications and growing area classification maps for you to consult:

http://www.doh.wa.gov/ehp/sf/sfpubs.htm#GrowingAreasPubs

Before you consume shellfish from your tidelands consult with the DOH shellfish program to make sure you have the most up-to date information.

DOH has the following classifications for commercial growing areas:

Approved: the area is not subject to contamination that presents an actual or potential public health hazard.  An Approved classification authorizes commercial shellfish harvest for direct marketing. 

Conditionally Approved: the area meets Approved criteria, but only during predictable periods.  For example, during dry weather a growing area may meet Approved water quality standards, but after a certain amount of rain falls (termed a "rainfall event") the water quality declines.  In this example, the Conditionally Approved area is temporarily closed to harvest after a rainfall event.  The length of closure is predetermined for each Conditionally Approved area, and is based on water sample data that shows the amount of time it takes for water quality to recover and again meet Approved criteria.  Once that time period has elapsed, the area is reopened.

Restricted: the area does not meet water quality standards for an Approved classification, but the DOH survey indicates only a limited degree of pollution from non-human sources.  Shellfish harvested from Restricted growing areas cannot be marketed directly.  They must be “relayed” to Approved growing area waters for a specified amount of time, allowing shellfish to naturally cleanse themselves of contaminates before they are harvested for market.

Prohibited : the DOH survey indicates that fecal material, pathogenic microorganisms, or poisonous or harmful substances may be present in concentrations that pose a health risk to shellfish consumers.  Growing areas adjacent to sewage treatment plant outfalls, marinas, and other persistent or unpredictable pollution sources are classified as Prohibited.  Growing areas that have not undergone a sanitary survey are also classified as Prohibited.  Commercial shellfish harvests are not allowed from Prohibited areas.  

 Closures due to biotoxins - red tide:

The DOH Biotoxin Program performs year-round monitoring of Paralytic Shellfish Poison (PSP, also known as "red tide"), and Amnesic Shellfish Poison (ASP, or domoic acid) in shellfish.  

The term "red tide" is a misnomer...paralytic shellfish poison and domoic acid poison are rarely associated with a red tinge to the water.  Both PSP and domoic acid can be present in large amounts when the water appears clear.  Reddish coloration of the water is more commonly associated with non-toxic organisms.

Biotoxins are caused by microscopic toxin-producing algae that naturally occur in marine waters, normally in amounts too small to be harmful.  However, a combination of warm temperatures, sunlight, and nutrient-rich waters can cause rapid plankton reproduction, or "blooms".  Molluscan shellfish (those that have a hinged shell, such as clams, mussels, oysters, geoduck, etc.) are filter feeders and ingest the algae into their systems, where toxins concentrate.  Paralytic shellfish poison  is caused by the phytoplankton Alexandrium catenella; domoic acid poison is caused by the dinoflagellate Pseudo-nitzschia pungens.   It is important to note that cooking does not remove these toxins from shellfish.  Cooking will kill the organisms, but the toxin remains.

Before you consume your shellfish, contact DOH at the PSP Hotline at (800) 562-5632 or check their Marine Biotoxin Bulletin to make sure your shellfish are safe to eat.

For more information: Department of Health Food Safety Shellfish Programs

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How fast will my shellfish grow?

Different growing conditions will lead to different growth rates. The following are general guidelines:

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Are there growing conditions that my oysters will not enjoy?

Sometimes you can't chose the tidelands you will use to grow shellfish. Consult the growing publications above to find the best areas on your tidelands to grow shellfish. The following factors will be very important:

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Are there predators that will kill my shellfish?

Both clams and oysters are valuable food to other types of wildlife before we humans harvest them!

Both clams and oysters can be harvested by animals, water birds, starfish and crabs that will burrow into the sand to find them. You can protect your seed from such predators by growing the seed in bags or other protective structures.

Both oysters and clams are also susceptible to predation by moon-snails. Moon snails will drill into clam and oyster shells and eat out the meat.

Oysters are also attacked by the Japanese oyster drill (Ceratostoma inornatum). The drill was imported from Japan with the first planting of Japanese oyster seed in Samish Bay, Washington. It is a marine snail which drills a small hole through the shell of the young oyster and eats the meat. This drill has been spread by the transplanting of oysters and has become established in many areas of the state. These drills do not migrate by themselves, and it is, therefore, possible to control their spread by a quarantine system designed to prevent them from being taken accidentally or purposely onto drill-free tidelands. This is why oysters from some areas con not be moved to other growing areas. Chapter 220-72 WAC of WDFW's regulations is a good starting place to find out if your tidelands are located in a drill infested area.

Finally, some oyster grounds may have dense populations of ghost shrimp which both soften the ground and cause burying of oysters. These crayfish-like animals live in the bottom and, through their digging and water pumping activities, honeycomb the bottom and constantly deposit subsurface material on the surface which will bury and kill oysters.

 

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Growing Oysters and Clams - Harvesting your Shellfish - Shellfish and the Environment - Resources and Links

Shellfish Gardening Home - Puget Sound Restoration Fund