Spreading oyster shell from a barge

How we restore

Oysters growing on a football
Oysters settled on trash in San Francisco Bay, at a site where oyster larvae are present in large numbers but hard substrate is lacking. This site was later selected for an oyster restoration project using substrate addition. Photo: Chela Zabin.

Most Olympia oyster restoration projects involve the addition of some type of hard substrate, which oysters require for attachment. This method works well in locations where naturally occurring populations of oysters produce sufficient larvae, but where hard substrate at the right tidal elevation is limited.

The most commonly used substrate is clean Pacific oyster (Crassostrea gigas) shell, which is significantly larger than Olympia shell. Some projects add layers of loose shell spread flat or in mounds, while others use bagged shell. Other projects, like those in San Francisco Bay, have used structures made of "baycrete" (a mixture of oyster shell and sand from the bay, and a small amount of Portland cement), Olympia oyster shells and clam shells strung on rope or attached to stakes. Which method is selected depends on local conditions and the goals of each project; for example, some projects aim to recreate the natural low-lying beds of Olympia oysters, while others have shoreline protection aims as well as oyster restoration goals.

A variety of restoration methods
A sample of the various types of restoration substrates and configurations used in Olympia oyster restoration. Clockwise from above left, small clusters of oyster shell placed amid eelgrass, large swaths of oyster shell placed on the shoreline, bagged oyster shell stacked in mounds and large concrete oyster balls. 

Other projects move oysters to locations where they are rare or absent. Many projects in Puget Sound and some of the other projects on the West Coast have used hatchery reared oysters as a restoration method. This method is particularly appropriate in locations where there are few naturally occurring larvae. Typically these native oysters are settled onto Pacific oyster shell, which is then deployed.

Close up of juvenile oysters settled on a bivalve shell.
Juvenile Olympia oysters settled on a gaper clam shell for restoration in Elkhorn Slough, CA. Photo: Chela Zabin.
Tiny Olympia oyster spat on bagged oyster shell
Tiny Olympia oyster spat settled onto Pacific oyster shell in mesh bags for restoration in Clallam County, WA. Photo: Puget Sound Restoration Fund.










About one-fifth of West Coast projects have involved moving either adult oysters or newly settled oysters from sites with plentiful oysters to sites where oysters were rare or completely absent.

Oyster restoration projects come in all sizes, from small-scale experiments exploring best methods to large scale projects that need industrial-sized methods to deploy. 

Using a water pump to disperse shell from a barge.
As part of a Puget Sound Restoration Fund project, Pacific oyster shell is dispersed from a barge using a high-powered hose for a large-scale effort in Dogfish Bay, WA. Photo: Shelly Solomon.