Study highlights successes of Virginia’s oyster restoration efforts

(Press-News.org) Virginia has made significant investments in the restoration of oyster reefs in the Chesapeake Bay, and now a study led by William & Mary’s Batten School & VIMS suggests those management practices are literally paying off in the Rappahannock River. The study, recently published in the Journal of Environmental Management, was led by Batten School of Coastal & Marine Sciences Ph.D. student Alexandria Marquardt, who presented the results to the Virginia Marine Resources Commission’s (VMRC) Shellfish Management Advisory Committee on February 19. 

In addition to supporting local economies, oysters filter the surrounding water removing algae and excess nutrients while clumping together to form large reefs that serve as habitat for many fish and marine animals. Though once abundant, oyster populations in the Chesapeake Bay collapsed in the mid-1980s due to a combination of overfishing and disease. While Virginia Institute of Marine Science has endeavored to increase wild oysters’ resistance to virulent pathogens, the VMRC regulates the fishery in Virginia and oversees efforts to restore oyster reefs. 

“Oyster restoration typically focuses on shell replenishment, in which oyster shells are spread over existing reefs on which juvenile oysters attach and grow. This was an exciting project, because it was the first to evaluate the benefits of replenishment activities both biologically and for the fishery,” said Marquardt, who collaborated on the study with faculty and scientists at the Batten School & VIMS and the VMRC. “Oyster reefs located in public fishing grounds are largely not studied, but we saw significant benefits from even modest replenishment. When combined with rotational harvests, the underlying reef structure was maintained and commercial harvests increased.”

The study showed that the density of juvenile oysters known as spat increased immediately following shell replenishment while the density of market-sized oysters peaked three years after, reinforcing the VMRC’s current 3-year rotational harvest protocol. Spat density, though highly variable, was highest in years coinciding with higher brown shell volumes, a measurement of reef health that refers to the amount of oysters and shell above the bottom sediment layer. Marine protected areas were shown to have higher market oyster densities and offer protection from commercial fishing for larger oysters, which may provide a valuable spawning function for the fishery.

VMRC began their shell replenishment program in 2000 and implemented rotational harvests in 2007. These practices have resulted in steady increases in brown shell volume throughout the Rappahannock River and increased the likelihood of watermen meeting daily harvest limits. Overall, the study showed that oyster harvests steadily increased with the improvement of the oyster reefs, with market oyster densities increasing substantially since 2018. 

Since the 2007-2008 harvest season, more than 500,000 bushels of oysters valued at more than $24 million were harvested from the Rappahannock River. The VMRC has invested more than $14 million toward replenishment in the river since 2000.

“It’s rewarding to see that science-based management of this fishery is providing benefits for both the environment and local economies,” said Marquardt. “I’m thankful for the opportunity to work with the VMRC and contribute to a sustainable oyster industry in Virginia.”

View a summary of the study.

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