Living shorelines are a nature-based approach to coastal protection that uses natural materials like plants, sand, rock and oyster shells to stabilize shorelines and protect them from erosion. 

Native oysters are a particularly effective component of living shorelines. Unlike traditional hard structures like seawalls, living shorelines work with nature to provide environmental benefits like habitat for wildlife, improved water quality and increased resilience to storms. Over time, as shores experience sea level rise, oysters are able to rise with the water.

“Hard structures, like sea walls or breakwaters, will not change over time with the environment, but oysters have that ability,” said Riley Hudock, a master’s student in the College of Earth, Ocean and Environment at the University of Delaware. “If the water is rising, then the reef will start to grow taller. Oysters are ecosystem engineers, and they provide a lot of ecosystem benefits.” 

Hudock recently evaluated the growth and mortality of two strains of farmed oysters: NEH ®, high salinity tolerant oysters, and DBX, medium and low salinity tolerant oysters, to determine which species would perform better in the Delaware Bay at varying depths and locations within the estuary. Her research was part of the Developing Engineering Practices for Ecosystem Design Solutions, or DEEDS project, funded through a Department of Defense appropriation. 

At UD’s Hugh R. Sharp Campus in Lewes, Hudock worked with Ed Hale, assistant professor in the School of Marine Science and Policy and fisheries and aquaculture specialist with Delaware Sea Grant, and Brendan Campbell, research associate, on the project. She evaluated how the strain of an oyster, tidal position and environmental variables affect oyster growth and survival. 

Working at the boat basin on the Sharp Campus and Port Mahon in Dover, Hudock examined how the oysters would perform in different environments. 

Hale said the two strains are “commonly used in oyster farming. We were kind of borrowing what we knew from the commercial production side to see if we could use it from a more practical, resilience-based application.” 

Hudock found the NEH ® oysters, the strain with higher salinity tolerance, showed better meat condition and better general growth performance when compared to the DBX oysters, particularly in Lewes, where they experience high salinity conditions. 

The findings were recently published in the Frontiers in Ecology and Evolution scientific journal. 

While NEH ® work better in these high salinity environments, Hudock recommends farmed oysters that are best suited to local environments. 

“Ultimately, you want to make your decision based on the available strains in the area and under what conditions those oyster strains grow best,” Hudock said. “Then we can make recommendations to help improve the efficiency of these installations because it is a slow and expensive process.”

Hudock said another aspect of her master’s thesis is related to the wild recruitment of oysters — when oysters reproduce on their own without being farmed or placed there by people. Having good wild recruitment is key, Hudock said, because this can lead to stable habitat for larvae, which is essential for a self-sustaining oyster reef.