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Sewage or vomit from a vessel was the most likely cause of an oyster contamination earlier this year that forced the temporary closure of five oyster farms on Mahurangi Harbour.
The Ministry of Primary Industries (MPI) warned people to not eat chilled oysters in February, and oysters harvested from the harbour from mid-January were recalled. The Ministry was alerted by local health authorities after 11 people became ill.
MPI spokesperson Piers Harrison said the oyster farms reopened last week, after testing found them to be clear of norovirus and the MPI investigation was completed.
“This discharge would have been from the waste of a person affected by or carrying the norovirus,” Mr Harrison said. “The norovirus-contaminated sewage or vomit would have drifted with the tide over oyster farms, contaminating the oysters, and anyone who ate those affected oysters.”
MPI conducted an extensive field investigation with assistance from the Auckland Harbourmaster. A number of home onsite sewerage systems were examined to ensure they weren’t leaking sewage into waterways or the harbour. MPI also inspected a number of yachts’ on-board sewerage systems.
As a result of the investigation, MPI has recommended Auckland Council follows up on some properties to ensure their onsite sewerage systems are functioning properly.
Signage will also be set up around the harbour, warning boaties that sewage is not to be discharged into the harbour.
The Resource Management (Marine Pollution) Regulations 1998 prohibit the discharge of untreated sewage within 500 metres of land or a marine farm, and in waters shallower than five metres.
