Mississippi projects aim at improving oyster reefs

December 27, 2021 GMT

GULFPORT, Miss. (AP) — A test project to raise tiny baby oysters on shells to add to oyster reefs has succeeded beyond expectations, says the head of Mississippi’s Department of Marine Resources.


The department obtained 98 million oyster larvae from the University of Southern Mississippi and Auburn University, and put them, in batches, into six 1,000-gallon (3,800-liter) tanks holding sea water and empty oyster shells.

They wound up with 17.6 million baby oysters, nearly 17 per shell, according to a news release.

The baby oysters, called spat, averaged about one-tenth of an inch (2.74 millimeters) across when the shells were added to “cultch plants” in Biloxi Bay. Those are areas where the department has set out shells and other hard surfaces that larvae can attach themselves to.

Oyster reefs are a coastal keystone, protecting coastlines from erosion, providing habitat for hundreds of other species, and filtering the water as they feed.

“Our MDMR staff have worked diligently on this project, and so far, the results have exceeded our expectations,” Joe Spraggins, the department’s executive director, said in a news release.

He said the $62,200 cost worked out to half a penny per baby oyster. The money came from Clean Water Act penalties paid by BP and codefendants.

The department did not pay for the larvae, said Rick Burris, the department’s chief scientific officer. Expenses included staffing, boat usage, equipment and supplies, including the oyster shells. The department will review the results to decide whether to continue.

The likely cost of larvae has not been evaluated but will be a factor in deciding whether to continue, Burris said in an email.

About 2% of the spat put into the bay may survive to adulthood, but there were far more on the shells than is likely in the wild, Burris wrote.

“The remote setting process takes away a lot of the mortality that occurs in the wild larval stage,” he said.

The department’s small-scale “Remote Oyster Setting Facility” used six tanks at the Port of Gulfport. Each went through six production cycles over five months. Just over 16% of the larvae settled onto shells and developed into spat, the news release said.

Overall, 46.8 cubic yards of spat-on-shell was set out.

MDMR staff monitored water quality, including temperature, salinity, dissolved oxygen and pH, throughout the production season.

The department’s other oyster reef projects include one that looks at both a possible way to improve artificial reefs and how such reefs affect threatened Gulf sturgeon.

Scientists from the department, the U.S. Army Engineer Research and Development Center in Vicksburg, and the universities of Southern Mississippi and Kentucky have chosen two sites that they want to use.

Dr. Mike Andres, assistant research professor at USM, graduate students from his lab and Corps researchers are tagging juvenile and subadult Gulf sturgeon in the Pearl and Pascagoula rivers for the study.

“Dr. Andres’ lab, along with ERDC researchers and collaborators from the University of Kentucky sampled sediments and potential Gulf sturgeon prey species in Mississippi Sound during August to gather preliminary data for these regions,” said Dr. Safra Altman, a research ecologist with ERDC’s Environmental Laboratory and the agency’s technical lead for the project.

One goal is to find whether adding extra limestone at the start, middle or end of oyster spawning season helps increase numbers of oysters.

The scientists also will use data from the acoustic telemetry tags to see whether sturgeon are in the area, and check whether sediment around the reefs holds large numbers of animals that sturgeon might nose out to eat.

Currently, all of Mississippi’s waters within the Mississippi Sound are federally designated critical habitat for Gulf sturgeon. However, scientists don’t know just how the fish use and interact with open bottom or oyster reefs in the sound.


This story was first published on Dec. 26, 2021. It was updated on Dec. 27, 2021 to show that the University of Southern Mississippi provided larvae, not Mississippi State University.