How to Breed Hardier Oysters
Although North Carolina’s oyster industry has seen a recent resurgence, growers have suffered from unexplained losses of up to 90% in the past few seasons. NC State University researchers are investigating whether specific genetic traits might help certain oyster lines survive better than others.
Love ‘em or hate ‘em, oysters have helped sustain our state’s economy throughout its history.
In fact, oysters were once so vital to North Carolina that we went to battle over them. Roughly 25 years after the Civil War ended, North Carolina declared another war of its own, over the rights to its oyster beds.
Oysters quickly became a valuable commodity in the Reconstruction-era South. And after armed poachers were eventually ousted from Maryland and Virginia’s then-depleted Chesapeake Bay, these oyster pirates made their way down to the sounds of North Carolina. So in 1891, the state legislature authorized citizens to take up arms against out-of-state dredgers, which could harvest in deeper waters — and would often gather both young and mature oysters indiscriminately.
The industry peaked in 1902 and then, in part due to irresponsible harvesting practices, steadily declined until the 80s, when disease wiped out most of the remaining oyster population. While wild oysters may be way past their economic prime, oyster aquaculture has the state’s industry back on the rise. And since 2019, Tal Ben-Horin, an assistant professor of shellfish pathology at NC State University, has been studying how to breed hardier oysters.
In May, the North Carolina Department of Environmental Quality granted Ben-Horin $200,000 to further research what can be learned from genetic lines of farmed oysters that survive mass mortality events caused by, for example, bacteria or parasites. Curious about why certain oysters survived, Ben-Horin and his research team plucked samples from aquatic farms, studied their genetic makeup and culled their genetic lines. They’ve already identified several lines in North Carolina that survived a mass mortality event.
“This money is going toward the hatchery work to produce those genetic lines, and then we’re going to deploy those genetic lines to our field sites and study them,” says Ben-Horin, whose home base is the Center for Marine Sciences and Technology (CMAST) in Morehead City.
New Threats to a Burgeoning Industry
Oyster aquaculture has grown into a nearly $30 million industry in North Carolina. And groups like the North Carolina Coastal Federation hope to see the industry grow to $100 million by 2030. For that to happen, though, oyster growers need help from researchers like Ben-Horin.
In recent years, farmers in North Carolina and other states in the Southeast have sporadically suffered from seemingly inexplicable mass mortality events — with some losing up to 90% of their oysters in a short timespan.
“We took the North Carolina lines that had survived a mortality event across multiple sites and started looking at this heritability question,” Ben-Horin says. “We have a portfolio of lines that have been through a mortality event on these commercial farms.”
The Department of Environmental Quality-funded research project will take over two years to complete, but Ben-Horin is optimistic that they’ll discover which genetic traits make it more likely that oyster beds will survive mass mortality events.
Lines that have survived multiple events show the most promise so far.
“This leads us to think maybe we can select for resilience in some capacity,” Ben-Horin says. “Maybe we can select desirable traits through breeding and then use those in production.”
Motivated by Unanswered Questions
Ben-Horin is working closely with UNC Wilmington’s Shellfish Research Hatchery on the research project. The hatchery has created seed oysters from the isolated genetic lines of survivors from the mass-mortality event and shared this broodstock with a local industry hatchery.
“The industry sites produce the oysters just like they would on a commercial scale,” Ben-Horin says. “Sometimes they do great. Sometimes they see lots of mortality.”
Should the results of this research ultimately help North Carolina grow its aquaculture industry, Ben-Horin will be happy. But it’s the basic research and never-ending cycle of unanswered questions that will always motivate him the most.
“The applied question of how shellfish farmers are responding to mortality events and resources that we can provide for them is really important, but often the day-to-day science is equally important on a lot of levels,” Ben-Horin says. “It’s really hard not to get really excited about these questions.”
This article is based on a news release from NC State’s College of Veterinary Medicine.
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