Shellfish can be affected by naturally occurring toxins (paralytic shellfish poisoning), as well as by viruses and bacteria.
Shellfish and seawater samples in the Bay of Plenty district are tested every week to ensure they are not contaminated with biotoxins (paralytic shellfish poison or PSP).
The Ministry for Primary Industries is responsible for issuing health warnings when shellfish are not safe to eat. Health warnings normally affect shellfish such as mussels, toheroa, pipi, tuatua, cockles, oysters, scallops, catseyes, pupu and kina (sea urchin).
Symptoms of shellfish poisoning include:
Numbness and tingling around the mouth or face
Difficulty swallowing or breathing
Double vision, and in severe cases, paralysis and respiratory failure
These symptoms occur within 12 hours and anyone experiencing these symptoms should seek medical advice immediately.
Gastrointestinal illness and symptoms (such as diarrhoea and vomiting) may also occur if shellfish are contaminated with bacteria and viruses.
Bacterial and viral contamination
The following areas are monitored by Bay of Plenty Regional Council for bacterial and viral contamination:
- Ohiwa Harbour - Uretara Channel, Eastern Ohiwa
Little Waihi - Beach by campground, boat ramp
Maketu - Marae end of Park Road
Tauranga Harbour - Pilot Bay, Tanners Point, Pio’s Beach, YellowPoint, Hunter Creek
Tauranga - Tilby Point
Waihi Beach - Estuary
For information on monitored areas in the Coromandel and Waikato, contact Waikato Regional Council. For pollution response, enquiries and after hours service freephone Waikato Regional Council on 0800 800 401.
Before collecting shellfish
Check that there is no current health warning advising against collecting and eating shellfish.
Also check the water. If you notice the water is murky collect shellfish from somewhere else.
Collect shellfish only from areas where the seawater is clean and not contaminated.
Proper handling, storage and cooking can also help lower the risk of illness from viruses and bacteria (but does not prevent illness from paralytic shellfish poisoning). Remember the gut of paua, crayfish and crabs should always be removed before cooking.
Shellfish Research Report
What's in our shellfish?
Towards the end of 2006 Environment Bay of Plenty (now called Bay of Plenty Regional Council), Tauranga City Council, Western Bay of Plenty District Council and Toi Te Ora - Public Health Service agreed it was necessary to obtain better information on the pathogen levels in shellfish so the public could be better informed of the risks of collecting and eating shellfish from local beds.
As both Tauranga Harbour and Waihi Estuary are used extensively for gathering and consumption of non-commercial shellfish, they were selected for monitoring.
Over the last few years the New Zealand Food Safety Authority has funded the development of norovirus testing for shellfish and was interested in proving the methodology in a field situation and also gathering data to support predictive modelling of viral contamination.
To this end these organisations agreed to fund a joint project to fill some of the current information gaps relating to microbiological contamination of shellfish and adjacent waters.
For more information about the study, view the resources below:
For information about current health warnings regarding shellfish - click here