Shellfish Restoration

Massachusetts hosts over 25 shellfish projects that use oysters, clams, quahogs, and scallops to achieve a range of goals that include restoration, denitrification, mitigation, and population enhancement.

This page is a work in progress, continually updated as new information regarding Massachusetts projects becomes available. The provided information has been improved by data contributed by the Towns of Falmouth, Mashpee, and Nantucket. If you have additional information you would like to contribute, please contact MIT Sea Grant.

Research Scientist

Oyster Restoration Best Practices

Variable

Best Practices

Site Selection

Restoration should occur in habitats where there have been oysters. The Massachusetts Division of Marine Fisheries provides an online map of suitable areas for oysters based on distribution since the 1970s.
In areas where sedimentation occurs in excess as a result of anthropogenic degradation, cultch is recommended to provide structure and shelter for juvenile oysters.
Eelgrass beds and intertidal flats should be avoided.
If a candidate site has high nitrogen input, it could benefit from oyster restoration from oysters’ role in denitrification. However, a water body with too much nitrogen can prevent oyster recovery by causing bottom-water hypoxia.

Cultch

The addition of cultch should occur only in historic oyster habitats. Otherwise, hardening the substrate would be considered habitat conversion and the project may not be approved by regulatory agencies.
Ideally, the cultch type should be oyster shell, but all types of cultch (concrete, porcelain, limestone, rock, shell, etc.) are more beneficial to oyster recruitment and community structure than bare sediment.
Shell material in cultch should be aged outside the water per shellfish planting guidelines.
Oysters seem to prefer larger pieces of shell, with cavities in which they can settle, as opposed to crushed shell.
The addition of adult oysters to cultch enhances oyster populations by encouraging settlement, as oysters settle preferentially on conspecifics.

Origin and Disease

Non-native species should not be used in restoration efforts.
The movement of shellfish between different water bodies can bring disease (Dermo, MSX) or invasive organisms; thus, shellfish should be tested for pathogens before introduction to a new area. Approved pathology labs are listed on the Division of Marine Fisheries website.
Maintaining high intraspecific diversity at a site benefits oyster populations and enhances natural recruitment.

Timing

The timing of reef construction and shell planting should coincide with the timing of oyster recruitment within an ecosystem, or the reef may be populated by other organisms.

Depth

Survival of juvenile and adult oysters does not appear to differ with depth.
At depths >4.5 m, there is a risk of bottom-water hypoxia and consequential mass mortality of oysters and other organisms.

Artificial Structure

Providing or ensuring a reef height greater than 0.3m is beneficial for the health of the reef, as growth and condition of oysters has been shown to be greatest at the crests of reefs.
The addition of adult oysters to reefs increases complexity of the reef and available surface area.

Oyster Bags

Bags should not be overpacked in order to leave space for oysters to settle and grow, and to allow water to flow and deliver food.
Bags should not be placed flat on the bottom of the water body; instead, they should be placed on racks or trays to prevent smothering by sedimentation.
Young oysters can be protected from the sun by covering the bags with burlap for the first few weeks.

To view this table with citations, click here.

Massachusetts hosts over 25 shellfish projects that use oysters, clams, quahogs, and scallops to achieve a range of goals that include restoration, denitrification, mitigation, and population enhancement.

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Carolina Bastidas

Oyster Restoration Best Practices

Variable

Best Practices

Variable	Best Practices
Site Selection	Restoration should occur in habitats where there have been oysters. The Massachusetts Division of Marine Fisheries provides an online map of suitable areas for oysters based on distribution since the 1970s. In areas where sedimentation occurs in excess as a result of anthropogenic degradation, cultch is recommended to provide structure and shelter for juvenile oysters. Eelgrass beds and intertidal flats should be avoided. If a candidate site has high nitrogen input, it could benefit from oyster restoration from oysters’ role in denitrification. However, a water body with too much nitrogen can prevent oyster recovery by causing bottom-water hypoxia.
Cultch	The addition of cultch should occur only in historic oyster habitats. Otherwise, hardening the substrate would be considered habitat conversion and the project may not be approved by regulatory agencies. Ideally, the cultch type should be oyster shell, but all types of cultch (concrete, porcelain, limestone, rock, shell, etc.) are more beneficial to oyster recruitment and community structure than bare sediment. Shell material in cultch should be aged outside the water per shellfish planting guidelines. Oysters seem to prefer larger pieces of shell, with cavities in which they can settle, as opposed to crushed shell. The addition of adult oysters to cultch enhances oyster populations by encouraging settlement, as oysters settle preferentially on conspecifics.
Origin and Disease	Non-native species should not be used in restoration efforts. The movement of shellfish between different water bodies can bring disease (Dermo, MSX) or invasive organisms; thus, shellfish should be tested for pathogens before introduction to a new area. Approved pathology labs are listed on the Division of Marine Fisheries website. Maintaining high intraspecific diversity at a site benefits oyster populations and enhances natural recruitment.
Timing	The timing of reef construction and shell planting should coincide with the timing of oyster recruitment within an ecosystem, or the reef may be populated by other organisms.
Depth	Survival of juvenile and adult oysters does not appear to differ with depth. At depths >4.5 m, there is a risk of bottom-water hypoxia and consequential mass mortality of oysters and other organisms.
Artificial Structure	Providing or ensuring a reef height greater than 0.3m is beneficial for the health of the reef, as growth and condition of oysters has been shown to be greatest at the crests of reefs. The addition of adult oysters to reefs increases complexity of the reef and available surface area.
Oyster Bags	Bags should not be overpacked in order to leave space for oysters to settle and grow, and to allow water to flow and deliver food. Bags should not be placed flat on the bottom of the water body; instead, they should be placed on racks or trays to prevent smothering by sedimentation. Young oysters can be protected from the sun by covering the bags with burlap for the first few weeks.