Long-term oyster reef restoration shows clear success in murky waters
Study of one of the world’s largest projects in Chesapeake Bay’s Harris Creek finds that restored reefs with complex structure support larger resident fish, sustain high oyster cover, and outperform harvested areas 6–10 years later
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Smithsonian Environmental Research Center (SERC) intern Liliana Bowman (right), a co-author on a new study highlighting the long-term success of oyster reef restoration efforts in the Chesapeake Bay, records sonar videos with SERC biologist Rob Aguilar.
view moreCredit: Matthew Ogburn/SERC
Large-scale oyster reef restoration in the Chesapeake Bay is successfully creating three-dimensional habitats that support larger, more diverse fish communities, according to new research from scientists at the University of Maryland, Baltimore County (UMBC), the Smithsonian Environmental Research Center, and the National Oceanic and Atmospheric Administration (NOAA). The study, published today in Ecosphere, provides compelling evidence that restoration efforts are shifting underwater ecosystems from communities dominated by small, transient schooling fish to those supporting larger, resident species.
The research focused on Harris Creek, on Maryland’s Eastern Shore, one of the world's largest oyster restoration projects, covering approximately 1.4 square kilometers. By combining underwater video with high-resolution imaging sonar, the team evaluated reef habitat and "nekton"—free-swimming animals like fish and turtles—six to 10 years after restoration was completed.
"Oyster restoration is important for lots of different stakeholders in Chesapeake Bay, so we wanted to know precisely how it influences reef habitat and the fish and crabs that use that habitat," says Allison Tracy, the study's lead author and assistant professor of marine biotechnology with UMBC at the Institute of Marine and Environmental Technology. "Large-scale oyster reef restoration in Chesapeake Bay has been a success,” Tracy adds, “and our study adds new and important metrics of success for one of the most high-profile sites in the project."
Completing the picture
The findings reveal that the restoration method matters. Reefs restored using a stone substrate plus juvenile oysters attached to adult oyster shells (called “spat-on-shell”) exhibited the highest habitat scores, showing greater vertical relief and structural complexity than reefs restored with spat-on-shell alone or reefs that had been continuously harvested. Restored reefs supported fewer total fish but significantly larger individual fish, with the highest abundance of fish exceeding 30 centimeters in length found on reefs restored with stone.
"The remote monitoring tools in this study make it unique," Tracy explains. "We combined a simple but effective GoPro-based method for studying reef habitat with an elegant, high-tech survey of animals using sonar. We looked at reef-associated animals through many different lenses to get a complete picture of the community of finfish, crabs, and rays."
The sonar data revealed a fundamental shift in how animals use these habitats. While harvested reefs and unrestored areas were dominated by small, schooling fish moving quickly through the water column, restored reefs supported more species that live and feed near the bottom. This suggests that the complex three-dimensional structure created by restored oyster reefs provides refuge and foraging opportunities for larger, commercially and ecologically valuable species.
"One of the key takeaways is that large fish in particular are taking notice of restored oyster reefs," Tracy notes. "Harris Creek is one of the most valuable case studies of oyster restoration in the world. It was a great opportunity to study how animals use these reefs."
Reef restoration efforts pay off
The timing of the study proved crucial to understanding restoration success. By surveying reefs at least seven years post-restoration, the researchers could assess long-term outcomes rather than immediate responses. The results indicate that Harris Creek's restored reefs are self-sustaining, maintaining high oyster cover and structural complexity years after construction.
"This project was a powerful combination of scientists from different institutions and career stages," Tracy adds. "We used the team's mix of expertise to carry out a unique and important study."
The research connects to broader efforts to restore Chesapeake Bay's oyster populations, which are at only 3 percent of historic levels due to overharvesting, disease, and environmental stressors. The study aligns with recent findings from NOAA and other collaborators, including current study co-author Jay Lazar, on large-scale oyster restoration success across the Bay system.
“Official monitoring of the large-scale restoration efforts only takes place three and six years after restoration, but studying these reefs in the long term is needed to ensure that they continue to support oyster populations and provide habitat for other animals,” says Matthew Ogburn, senior author on the new paper and a senior scientist at the Smithsonian Environmental Research Center. “This study shows that underwater video can help fill this need.”
The study's innovative approach—merging accessible video technology with sophisticated sonar imaging—offers a template for monitoring subtidal reefs in murky estuaries where traditional sampling methods face limitations. As restoration efforts expand globally, these remote sensing tools could help managers assess habitat quality and ecosystem services more efficiently and cost-effectively.
By studying reef habitat years after restoration, "we expected to be able to see how the efforts paid off—and they did pay off," Tracy says. The findings suggest that investing in structural complexity—particularly through substrate enhancement with stone and protecting restored reefs from harvest—can accelerate the return of valuable fish communities and support the long-term health of the Chesapeake Bay.
Allison Tracy, assistant professor of marine biotechnology at UMBC, lowers an underwater cameras into the Chesapake Bay to collect data for her newly published study on the effects of oyster reef restoration.
Credit
Matthew Ogburn/SERC
Journal
Ecosphere
Method of Research
Observational study
Subject of Research
Animals
Article Title
Oyster reef habitat characteristics and nekton communities vary with restoration method in a large-scale project
Article Publication Date
15-Sep-2026
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