For the oyster industry in the Canadian province of Prince Edward Island (PEI), this winter has been no ordinary offseason.
Less than a year ago, Multinucleate Sphere Unknown (MSX), a disease caused by the parasite Haplosporidium nelsoni, was first discovered on PEI, and oyster farmers and harvesters are now anxiously waiting to see what will become of their livelihood when the ice thaws.
“Everybody's kind of holding their breath, not sure what the spring will bring when we raise our equipment,” Aaron Sweet, a fourth-generation farmer and the owner of PEI oyster-farming firm Sweet Oyster Co., said. “We wish we would have had insurance for this type of thing, but now that the disease is here, you can't really insure a burning building.”
Though the industry is waiting with bated breath, at least so far, the impacts of MSX have been minimal, according to Bob Creed, the executive director of the Prince Edward Island Seafood Processors Association.
“Overall, 2024 was a pretty good year. There were some fatalities in the spring fishery, but the commercial fall fishery was positive,” Creed said. “We’re in the early days of the detection of MSX, so it’s still evolving.”
What remains unclear, however, is how quickly MSX will spread and whether it will lead to mortalities.
According to data from past MSX infections in the U.S. and Nova Scotia, the time frame from detection of MSX to mortality can vary from several weeks, to up to 10 years, to no mortalities occurring at all.
“For high mortality, you need to have the right combination of host, environment, and pathogen,” said Ryan Carnegie, a professor of marine science at the Virginia Institute of Marine Science (VIMS), in a study titled “Living and Working with MSX – an Oyster Industry Perspective,” which was prepared for the PEI aquaculture industry. “Sometimes, it is very quick, but some cases present no mortality. Or, it takes a long time to reach a mortality event. In some areas, MSX was detected decades prior to a major mortality event.”
When MSX was discovered in Cape Breton, Nova Scotia, in 2002, the time between discovery and mortality varied greatly depending on the area. In some areas, oysters never experienced mortality, but in areas like the northeastern Nyanza Bay, oysters died around a year after detection...
