Shellfish aquaculture is America’s largest and fastest-growing marine aquaculture sector. Along with that growth, growers and regulators face more stringent post-harvest treatment requirements to counter the increase in illnesses from the common pathogenic bacteria vibrio during warmer months.
Current post-harvest treatments to remove vibrio change the taste, are unpopular with consumers, or both, and remain prohibitively expensive and largely unavailable to most in an industry dominated by thousands of small, independent farmers. One method that works with coliform bacteria, but not with vibrios, is depuration—holding live bivalves in tanks of clean, flowing seawater where they continuously filter water and naturally expel pathogens from their gills and intestinal tracts. This process is also designed to prevent recontamination.
Better water disinfection may be key as a post-harvest treatment for vibrios.
We began testing two related, proprietary technologies: one, a water purification process, drives insoluble substances to nano-sized dimensions; the other, a photo-catalytic oxidation, can deliver and transport ozone and related biocidal gases into oyster tissues, destroying pathogens with higher efficiencies than any other comparable technology. We are assessing these technologies individually and in combination to create an environment that is lethal to pathogens yet benign to the shellfish being treated.
Both technologies work well in other industrial and aquaculture applications, but had never been tested with filter-feeding shellfish.
In pilot studies funded through Delaware Sea Grant and the manufacturer (Puradigm), we assessed the suitability of using these technologies with live oysters, providing baseline data on oyster survivability. This work may improve consumer safety by reducing vibrio and other pathogen (such as norovirus) levels in live oysters through accessible, inexpensive, non-lethal, post-harvest processing. Such treatments also help to build and diversify the shellfish aquaculture industry, positioning it for new markets.
Partners: Delaware State University, Department of Agriculture and Natural Resources; Ocean Equities, LLC; Virginia Seafood Agricultural Research and Extension Center; Delaware Department of Natural Resources and Environmental Control, Puradigm, LLC