Sick Oysters
© ONE NewsJuvenile oysters or 'spat'.
Scientists are trying to determine the cause of a mystery illness hitting oyster stocks on North Island farms.

The disease, which kills juvenile oysters, or spat, has been found on farms in Northland, Bay of Plenty and Waikato.

A 20-strong MAF team is working around the clock, testing the DNA of dead spat for traces of lethal pathogens.

Over 500 tissue samples have been taken and MAF hopes to have an answer next week.

New Zealand exports millions of Pacific oysters to Asia and Australia, bringing in around $30 million each year.

Callum McCallum runs New Zealand's third largest farm and says that the situation is bad for farmers.

The disease attacks the young oysters and farmers say sales this season are unlikely to be affected, but the impact may be felt next year.

"These are oysters that were destined for export markets next year, so clearly there are not going to be as many going out," said McCallum.

The disease does not pose a health risk to consumers, and so far Bluff oysters have not been affected.

Watch video here.