Deadly algal bloom returns

By KATHERINE HOBY

A toxic algal bloom that has killed thousands of fish in the Orewa area is the same one that poisoned more than 100 people and paralysed the shellfish export industry 10 years ago.

At least 10,000 fish have been washed up on Orewa Beach, Hatfields Beach and Red Beach over the past four days.

Most have been estuary and shallow water dwellers, such as flounder and eels.

Auckland Regional Council spokesman Eddie Grogan said dead fish found in the Waiwera Estuary were also suspected to be victims of the bloom.

Oyster farmers further north in the Mahurangi Harbour, near Warkworth, have been monitoring shellfish for toxic algae but have found nothing, says Jim Dollimore, of Bio Marine.

He said harvesting would stop as soon as any toxin was detected, because shellfish exporters would not take the slightest risk. Oyster and mussel farming sites in the gulf and on the West Coast were monitored year round

Mr Grogan said if the bloom was present it would probably kill oysters, and so would be easily identifiable.

Some farmers have just started reharvesting after a two-month ban on farming imposed in July by MAF and Auckland Public Health after raw sewage was pumped into the local river.

"They were told about this on Friday and it's just a waiting game now," he said.



Signs have gone up at the affected beaches warning members of the public not to collect fish or swim until further notice.

"Until we know more about this toxic bloom and its likely effects it is important the public heed this warning," said Mr Grogan.

Niwa scientist Dr Hoe Chang said the bloom toxins destroyed the gills of the fish, causing them to suffocate.

He said the bloom involved was the same one that surfaced in 1992.

It spread down much of the North Island coastline to include some of the country's richest shellfish beds, including those in the Marlborough Sounds.

Those eating the shellfish reported heat-sensitive skin, aching limbs and joints, and numb lips.

There have been no reports of people being affected this time.

Mr Grogan said the next task was to determine how widespread the bloom was, and who might be affected. "Public protection is high on the agenda."

He said that a toxic algal bloom was a naturally occurring problem which might have had an environmental trigger such as warmer weather.

He urged people to call the Enviroline on 0800-80-60-40 if they noticed anything out of the ordinary.

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