Smithfield’s oyster castles attracting more than shellfish

Published 3:43 pm Tuesday, August 15, 2023

Oyster castles lining the bank of Cypress Creek in Smithfield’s Windsor Castle Park have become a habitat for more than just shellfish.

Ella DiPetto, a third-year doctoral student at Old Dominion University, has undertaken a yearlong study of how birds and mammals use the battlement-shaped cinderblock structures.

“Oyster castles, as part of living shorelines, are being installed rapidly across Virginia’s coastline to protect land from erosion and enhance coastal ecosystems, but we are still unsure how these projects affect birds and mammals,” DiPetto said. “This is one of the first studies to observe birds and mammals along living shorelines projects, and will help inform coastal community members and scientists about the benefits these structures provide to wildlife.”

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The castles are intended to create artificial oyster reefs, which help purify the water by feeding off organic material that finds its way into the creek. Without the oysters, wind that blows fertilizer and dust from nearby farms into the creek can spur algae growth and potentially drop the water’s oxygen level below what’s needed to provide a natural habitat for fish.

The castles also form a barrier to slow the erosion of the shoreline, and can help stem Virginia’s declining oyster population. According to DiPetto, oysters are at 85% of their historic abundance in state waterways, largely due to excessive fishing.

But it’s what’s happening above the water that’s most interesting to her.

In 2022, DiPetto and her team of undergraduate researchers placed night-vision cameras at 10 oyster castle sites spanning Virginia Beach to Smithfield, automating them to take one photo per minute, 24 hours per day from May through December. They did the same at unaltered sections of shoreline at each location.

She and her team have now started going through more than 2.5 million photos one by one to see which show animals.

As of June when DiPetto presented the preliminary results of her research at Windsor Castle Park, she and her team had identified roughly 7,000 photos as showing at least one animal. The photos from the park showed 649 animals in some way using the oyster castles versus only 191 at the unrestored section of Cypress Creek’s shoreline, giving credence to her theory that the benefits of the castles extend above the waterline.

Raccoons accounted for 445, or 68%, of the animal sightings at Windsor Castle Park’s oyster castles, while only 49 raccoons were sighted at the unaltered section of shoreline. The great blue heron was another top user, with 147 sightings at the castles compared to 68 at the unaltered shoreline.

One photo captured a rare diamondback terrapin – the only turtle in the United States that lives exclusively in brackish saltwater. The Chesapeake Bay Program, a multi-state effort to reduce pollution and restore the bay’s wildlife populations, lists diamondback populations in the Chesapeake and its tributaries as “threatened.”

Windsor Castle Park’s shoreline is home to the newest of the 10 oyster castles DiPetto and her team visited. A team of 43 volunteers, including members of the Virginia Master Naturalists and workers from the town’s anchor employer, Smithfield Foods, constructed the castles and planted over 1,000 plugs of native grasses in 2021. The James River Association, a nonprofit organization that monitors and advocates for the river and its tributaries, funded the project with an $80,000 grant from the National Fish and Wildlife Foundation as one of three oyster castle demonstration sites across Isle of Wight, Surry and Prince George counties.

A healthy oyster reef, DiPetto said, should have at least 50 oysters per square meter. The average at Windsor Castle Park when she measured was 29.

“The trajectory of the relatively young living shoreline at Windsor Castle Park is positive, and it is already proving to be successful in shoreline stability and in enhancing the coastal habitat,” DiPetto said. “The planted marsh is flourishing and is protected from boat wakes and storms by the oyster castles, which themselves provide a habitat for a variety of coastal creatures. I am hopeful that as the shoreline continues to evolve, the oyster population will grow, bringing with it increased water quality and habitat benefits.”

DiPetto, a Portsmouth resident, majored in wildlife conservation at Virginia Tech for her undergraduate degree, then did songbird research before joining an oyster restoration organization. At ODU, she works under Eric Walters, professor and director of the Zoological Museum at ODU’s Department of Biological Sciences.

“I have always been passionate about the outdoors, and I knew from a young age that I wanted to have a job where I was constantly learning about the world around me,” DiPetto said.

“What truly solidified my passion was the realization of the pressing need to protect both our natural environment and the community from environmental hazards like the effects of climate change,” DiPetto said. “This field presents a unique blend of scientific knowledge, conservation efforts, and social impact and that is why I do what I do.”