People are advised not to collect or eat shellfish from the south of Mahurangi Harbour around Whangaparaoa Peninsula.
A toxin found in shellfish that has not been detected in this area since the 1990s is back, leading to a public health warning from the Ministry of Primary Industries (MPI).
Signs were posted at beaches, boat ramps and popular shellfish gathering sites around Whangaparaoa Peninsula up to the southern end of the Mahurangi Harbour on June 3 advising people not to collect or consume shellfish because of the presence of Paralytic Shellfish Poisoning.
MPI specialist adviser Brian Roughan says the toxin was discovered during routine testing of water and shellfish samples.
He says further testing revealed the toxin to be above the safe level – 0.8mg/kg is considered safe by MPI, and levels locally were up to 1.0 mg/kg.
Eating affected shellfish can cause a range of serious symptoms including dizziness, vomiting and diarrhoea, numbness around the face, hands and feet, or even paralysis.
MPI advises that while Paralytic Shellfish Poisoning hasn’t caused deaths in New Zealand, there have been several cases of hospitalisation and admission to intensive care in the Bay of Plenty when people continued collecting shellfish when a warning was in place.
The poisoning is caused by an algal bloom, which usually occurs from natural causes. Toxins are released into the shellfish when they eat the algae.
Mr Roughan says that typically toxicity can persist for weeks or even months and may recur as the organism produces cysts that bloom again when conditions are favourable.
MPI is undertaking further testing to check how widespread the toxicity is and the area currently subject to warning may change when further results are received.
As Hibiscus Matters went to print, the alert was still in place. The situation is being monitored and updates can be found on our website, or at mpi.govt.nz, where you can also sign up to email updates for toxic algal blooms.