Toxin levels mean ban stays

The ban goes along the coastline from Tairua to the Eastern Bay of Plenty.

A health warning against eating shellfish collected along the Eastern and Western Bay of Plenty coastline will not be lifted until toxin levels drop, officials say.

Toi Te Ora Public Health Service medical officer of health Jim Miller said recent sample results showed it was still unsafe to eat shellfish taken from the region's beaches.

The alert has been in place for more than two years.

"We won't consider lifting the warning until we see the levels drop in at least two or three samples in a row as results can be variable and unpredictable."

The latest warning came before an outbreak of paralytic shellfish poisoning in 2012 when 27 local residents ate contaminated shellfish. A number were hospitalised.

The warning applies to all bi-valve shellfish including mussels, pipi, tuatua, cockles, oysters, scallops, cat's eyes, snails and kina.

It covers the coastline from Tairua to Whakatane Heads in the Eastern Bay of Plenty. The warning includes Tauranga Harbour, Maketu and Waihi estuaries, Matakana and Motiti islands, and all other islands along this coastline.

Previously, a long-term warning was in place from December 2009 to March 2011. Tilby Point has a permanent health warning.

Bay of Plenty Regional Council science manager Rob Donald says the warning for shellfish is due to elevated levels of PSP toxins.

"There is nothing the regional council can do about the presence of PSP, as the algae that cause the problem are naturally occurring in the ocean."

Water is monitored regularly at about 80 river, stream, estuary and beach sites. The council tested for faecal coliforms, e.coli and enterococci, all indicators of faecal contamination.

Elevated levels meant there was a heightened risk of illness from viruses, giardia and pathogenic bacteria.

But water quality had been fine.

"This year, the water quality has been good with a few cases of elevated faecal coliform levels that quickly returned to low levels."

However, Tilby Point had a number of sources of faecal contamination including the occasional sewage overflow, septic tanks and inputs from the Wairoa River.

The council was working with communities to tackle the issue.

Shellfish were filter feeders and could directly feed on bacteria and other microscopic organisms from faecal contamination, Mr Donald said.

"These can accumulate in the gut of the shellfish and can in turn be consumed by people."