Shell-Based Reefs

Loose Shell Loose oyster shell is usually scattered easily by wave action. It is valuable for habitat enhancement where rapid siltation is not a problem.

Oyster Shell Bags Oyster shell bags can be placed along an eroding marsh edge similar to fiber logs.

Shell Bag Sill Oyster shell bags can be stacked like a sill to contain sand fill and support a planted tidal marsh.

Shell-based living shoreline reefs are designed with loose or contained shell. Loose, uncontained shell is highly suitable for shellfish recruitment, but is not usually effective for reducing wave height and energy except for very low energy settings. Contained shell in bags or cages can be placed in similar arrangements as stone sills for better wave attenuation. Shell-based reefs located next to natural or planted tidal marshes will increase the living shoreline habitat diversity.

Suitable Sites

Evidence of healthy native shellfish population in vicinity, e.g. oyster beds and/or ribbed mussels
Salinity always above 10 ppt; sites with salinity below 5 ppt are not suitable for growing oysters
Water depth at least 1 foot at low tide; intertidal reefs are subject to freezing and winter die-off
Firm bottom, not soft mud

Guidelines for Shell-Based Reefs

Use shell material from a local, sustainable source like restaurant recycling programs or discarded shells from commercial seafood businesses. Natural shellfish reefs should not be harvested for this purpose.
Use biodegradable, non-plastic containment materials
Intertidal reefs must withstand wave action, wave overtopping and extreme temperature stresses; place shell so it is not carried away by normal wave action
Subtidal reefs may need to be marked as navigation hazards
Promptly remove failed or damaged materials