Herring Bay's Oyster Habitat

Oysters grow in a variety of physical conditions around the world, but they like some environments better than others. While oysters thrived in Herring Bay in the past, the challenge today is to jump-start their growth in an environment that has changed. Here is a review of some of the basic physical features we know are key to having happy, healthy oysters.

What physical conditions do oysters need to grow?

Oyster larvae need firm surfaces to grow on, such as shells, rocks, and other hard surfaces. The eastern oyster species native to the Chesapeake (Crassostrea virginica) flourishes in brackish waters, favoring the salinity in mesohaline (5 to 18 parts per thousand (ppt) and polyhaline (18 ppt to 30 ppt) waters. Oysters can grow in waters of varying depths, but being exposed to freezing air can kill them. Recent research suggests that oyster production is higher on subtidal reefs (those that are always under water). Water depths of 9 feet to 18 feet work well for oysters.

Is the “bottom” of Herring Bay suitable for oyster restoration?

Herring Bay has significant areas of “hard” bottom that could support oyster restoration. A DNR survey done over the 1974 to 1983 period estimated that the sanctuary had over 5,000 acres of oyster reef habitat, but continued sedimentation and other factors may have reduced that amount. Given those changing conditions, sites being considered for restoration are probed to determine the depth of the sediment and extent of any “cultch” (such as old oyster shells that support the growth of juvenile oysters) before being approved.

Are the salinity levels in Herring Bay suitable for oyster restoration?

Herring Bay has mesohaline waters and is classified as a “medium-salinity” zone region (Zone 2). While monitoring data suggest Herring Bay’s salinity is generally lower than in some other sanctuaries in Zone 2 (such as Harris Creek on the Choptank River), Herring Bay’s salinity is higher than in other sanctuaries in Anne Arundel County (which are in salinity Zone 1).

Is the water depth in Herring Bay suitable for oyster restoration?

The water depths on the Yates bars in Herring Bay generally range from 8 feet to about 20 feet. To date, the sites chosen for oyster restoration in the Herring Bay Sanctuary have water depths ranging from about 9 feet to 18 feet.

Have the citizen-sponsored restoration projects been successful?

The results are positive. In the fall of 2022, a team of divers surveyed the AHB-sponsored reef and found an average of 236 live oysters per square meter. That was well above the standard restoration metric of 50 oysters per square meter. Importantly, the reef also showed evidence of the three-dimensional structures that provide beneficial habitat for other species. Those survey results are summarized in AHB’s 2022 Oyster Monitoring Report.