What it takes to build a reef
Oyster restoration is not easy or cheap. The process starts by breeding microscopic larvae and ends with the heavy machinery—or strong backs—delivering juvenile oysters to a home on the bottom of the Bay. Multiply the dollars and cents by the billions of larvae needed across the expanse of the Chesapeake Bay, and you’re “talking real money!” Here is a brief review of what it takes to “build a reef.”
How do you “build a reef” in a sanctuary?
All oyster reefs need a solid foundation. Herring Bay is fortunate to have significant areas of hard bottom, which generally makes it possible to begin planting without needing to add man-made materials like rocks or concrete for the base.
Oyster larvae are generally grown at oyster hatcheries. Once they are large enough, the larvae are put into tanks where they attach to oyster or other types of shells. At that point, they are known as “spat-on-shell,” or juvenile oysters.
Once they are “set” on the shell, the juvenile oysters are loaded into bags or boats for distribution to buyers.
Large distributors of juvenile oysters, such as the Oyster Recovery Partnership (ORP), have specially designed boats that pour the juvenile oysters onto the reef.
Volunteer plantings of bags of juvenile oysters are backbreaking work. When planting spat on AHB’s initial test site, AHB volunteers loaded 25 pound bags onto trucks at a hatchery, drove them to Herring Bay, unpacked and reloaded them onto a boat, sliced the bags open, and then hoisted the spat-on-shell overboard.
Detailed monitoring is done at 3- and 6-year junctures under permits from DNR. Underwater imagery developed by the Smithsonian Environmental Research Center (SERC) also can be used to check on the reef.
How many juvenile oysters need to be planted per acre?
DNR recommends initial plantings of 4 to 6 million juvenile oysters per acre, supplemented if needed by a second seeding of about 2 million per acre. It is ideal to plant oysters in 2 to 3-year cycles. Having a mix of different ages helps with reproduction.
How many juvenile oysters planted on a reef survive to adulthood?
Survival rates vary depending on numerous factors. Estimates range from a low of 10 percent to a high of over 90 percent. Survival rates tend to be higher if the juvenile oysters overwinter in cages, which reduces risks like predation.
How many juvenile oysters would it take to restore oysters in the Herring Bay?
DNR has restoration metrics for “tributary-scale restoration that are based on the extent of a sanctuary’s historical and currently restorable oyster habitat.” There are no estimates at this time for the scale of planting needed to restore Herring Bay because there are no baseline metrics for the sanctuary’s current restoration potential. The sizes of the sites being restored over the 2014-2025 period in Maryland’s five priority tributaries range from 60 acres to over 400 acres. As of the end of 2021, DNR had planted nearly 6 billion juvenile oysters in sanctuaries in those five tributaries. Funding for those five projects came from federal and state agencies.
How expensive is oyster restoration?
Costs vary depending on economies of scale, need for supplemental substrate, and method of deployment. DNR expects to spend $676,200 of the Ever Forward funding to plant 147 million juvenile oysters—60 million in the Herring Bay Sanctuary and 87 million in areas harvested by watermen—or an average of $4,600 per million juvenile oysters.