Man-Made Reefs Bring Back Oysters

The team expects that rebuilding the oyster industry also will boost recreational fishing in Pamlico Sound.

Oystering has been the livelihood of generations of coastal North Carolina residents, but the industry has been in decline for decades. Giant steel-claw dredges used to harvest the shellfish around the turn of the 20th century destroyed much of the oyster habitat in the coastal sounds. So, scuba-loving researcher Dr. David Eggleston is participating in a $5 million Recovery Act grant from the National Oceanic and Atmospheric Administration to create artificial reefs that are helping rejuvenate the state’s oyster industry.

A professor in the Department of Marine, Atmospheric and Earth Sciences, Eggleston has worked with the state Division of Marine Fisheries (DMF) to create 10 oyster sanctuaries in Pamlico Sound. He studied the numbers and distribution of oyster larvae in the sound, as well as the location of food sources and the impact of currents, to develop a model that suggested good locations for the sanctuaries. “There are tons of larvae out there,” Eggleston says. “What’s limited development of oysters in certain areas is a lack of places for them to settle and form their shells.”

To rectify that problem, the state has restored and created reefs in the sanctuaries in recent years. The N.C. Coastal Federation and DMF are leading the overall $5 million project to build reefs near Oregon Inlet and Cape Hatteras. Earlier research projects by Eggleston and colleagues — including several funded by North Carolina Sea Grant and the N.C. Fishery Resource Grant Program, both administered through NC State — had identified target sites. The Recovery Act project created more than 150 jobs, Eggleston says, as nearly 55,000 tons of limestone was quarried and trucked to the sound, carried by barge to the sites and dropped into 364 underwater mounds. Eggleston and his research team dove to the sites and checked samples of the rocks. “You couldn’t count the number of oysters forming, there were so many,” he says, estimating a fivefold increase in the density of oysters. The divers also spotted numerous fish in the area, from sheepshead to speckled trout to croaker. The team expects that rebuilding the oyster industry also will boost recreational fishing in Pamlico Sound. The NC State research totaled $225,000 including the diving and aerial surveys of fishing at the sites, a study that included Sea Grant’s Brian Efland.

Because a large number of boring sponges also have taken up residence on the reef near Hatteras Inlet, Eggleston is now studying whether materials like granite or concrete should be used to build reefs in very salty water. The holes that the sponges bore can weaken the limestone boulders, which could threaten the integrity of the reef. But Eggleston says more study is needed to determine if the sponges are an integral part of an oyster reef ecosystem. “We need to continue building the footprint of these reefs,” he says. “Creating an interconnected framework (among the sanctuaries) will help them become self-sufficient.”

 

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Restored reefs have seen a fivefold increase in oyster density, says Dr. David Eggleston, whose dive team tallied the changes.