"Devastating," is how one wild oyster fishery in Southland is describing the first discovery of a deadly parasite in Foveaux Strait.
While it is not harmful to humans, if it's left unmanaged it could severely impact the future of the southern delicacy.
News a parasite has been found in the oysters' natural habitat is something no one wanted to hear.
"It's pretty devastating news," Graeme Wright from Barnes Wild Bluff Oysters told 1 NEWS.
MPI biosecurity manager Cath Duthie is similarly disappointed.
"We were really disappointed... This is certainly not the news that we wanted," she says
Routine sampling found the parasite, bonamia ostrea, in three wild oysters in Foveaux Strait.
"This parasite does kill oysters... We don't know at this point at what degree it's going to impact oysters in New Zealand," Duthie says.
It's no stranger to New Zealand waters. The disease was first discovered in oysters near the Marlborough Sounds in 2015.
It was discovered again two years later in Big Glory Bay near Stewart Island, leading to a major cull of farmed shellfish to contain the spread.
This Foveaux Strait discovery is the first time it has been found there.
"I think there's always risk at the end of the day. You can't stop it spreading in water," Wright says.
"it was always a risk. It was something we hoped would never happen. But now it's here, we'll just have to deal with it."
Authorities say there is no health risk to humans so the oysters are safe to eat, and the area affected hasn't been touched by fishers this season.
The real concern is, if the disease spreads it could diminish the highly treasured shellfish.
MPI officials were in Invercargill today with a rāhui, or fishing ban, to be put in place next week as they investigate.
"I'm really confident that we've got a really good group working together that we can hopefully get some robust action," Duthie says.
"It's always concerning when things like this are found in the wild, and particularly for such an iconic species."
The mission now is to protect a shellfish that's become an important part of the region's identity and economy.