Deadly toxin threatens multi-million dollar shellfish industry

8.00am

A potentially deadly toxin has led to a warning to stop gathering shellfish in the Bay of Islands, putting at risk a multi-million-dollar export oyster industry.

Shellfish in the Bay of Islands have shown the presence of Paralytic Shellfish Poisoning (PSP) toxin at more than three times the safe health limit, health officials say.

"A safe level is 80mcg per 100g of flesh. The sample showed 263mcg per 100g of flesh," Northland Health shellfish co-ordinator Neil Silver said.

The shellfish gathering warning extends from Cape Brett to Howe Pt. Other areas on the east coast, north and south of the Bay of Islands show the presence below regulatory level. However, it is possible that the area covered by the warning could be extended.

The symptoms of PSP include numbness and tingling around the mouth, face or extremities; difficulty swallowing and breathing, dizziness, double vision and paralysis.

PSP toxin can cause death although no fatalities from PSP have been reported in New Zealand to date. There is no antidote to the toxin.

There have been no reports of people displaying PSP symptoms in the Bay of Islands.

"If they show any of the symptoms they should go and see their doctor as a matter of urgency," Mr Silver said.

It can take up to 12 hours for symptoms to develop.

An influx of visitors to the Bay of Islands over Easter increased the risk of people collecting shellfish in the area, he said.

Health officials believe the toxin is being passed onto shellfish from an algae bloom called Alexandrium catenella.

The toxin has been detected in the Bay of Islands before and was present on the West Coast last year.

There have been several outbreaks of disease related to Bay of Islands shellfish in the past few years.

These include a hepatitis A outbreak which affected 14 people involved in collecting contaminated mussels from Moturoa Island in 1999.

Traces of the Norwalk gastroenteritis virus were recorded in 1994, 1999 and again in 2001 in several Auckland restaurants, and were linked to contaminated oysters from the Waikare Inlet.

Bay of Islands oyster farmers' spokesman Charlie Davenport said there was little the farmers could do about the latest scare.

"It's a natural phenomenon and it might take a big storm to churn it up and get rid of it," Mr Davenport said. "But the farms will have to close and everybody will be peeved off about it."

It was not worth putting the export market at risk for the sake of waiting a few days for it to clear, he said.

The Bay's oyster industry was conservatively worth $30 million a year.

"It's a bit of a nuisance. But the oysters are not that fat at the moment anyway and they will still be there next week," he said.

There are 19 oyster farms in Orongo Bay, 21 in the Waikare Inlet (although 18 Waikare Inlet farms have already been closed due to the Norwalk virus), 10 in Kerikeri Inlet, four in Te Puna Inlet and one in Paroa Bay.

Aquaculture Federation chairman Bevan Wilkie said halting shellfish gathering in the Bay of Islands would effect a multi-million-dollar industry.

He said 86 per cent of Northland's export oysters were farmed in the Bay.

Only Seafood restaurant owner Calvin Shepherd, of Paihia, did not envisage the ban having a major effect on his business.

"The only real effect is that we will have to bring oysters in from outside the area," Mr Shepherd said yesterday.

- NORTHERN ADVOCATE (WHANGAREI)

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