New Zealand Food Safety is advising people to stay safe from food poisoning by cooking mussels thoroughly before eating them. Read more here.
Shellfish are an important food source for many people in New Zealand. Unfortunately, shellfish can be affected by naturally occurring toxins (such as paralytic shellfish poisoning), viruses and bacteria.
You should avoid collecting and eating shellfish from areas where:
- Warning signs are displayed
- Pipes or culverts run down to the waterway
- sewage or stormwater is discharged or there are lots of houses nearby
- farm animals are grazing nearby
- there may be industrial pollution
- boats may discharge sewage, or near wharves and marinas in general
Do not collect shellfish after heavy rain as storms may flush sewage overflow or farm run-off downstream which contaminates the water. After the water has run clear for a few days shellfish should be safer to collect again.
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 affected by toxins. Toxins 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.
Bacterial and viral contamination
Gastrointestinal illness and symptoms (such as diarrhoea and vomiting) may occur if shellfish are contaminated with bacteria and viruses. The Bay of Plenty Regional Council monitors several sites for bacterial and viral contamination of shellfish. Health warnings are displayed here.
- Maketu - surf club
Ohiwa Harbour - boat ramp
Ōhope Beach - surf club and Moana Street
Tauranga Harbour - Bowentown
Tauranga Harbour - Te Puna
Tauranga Harbour - Tilby Point
Little Waihi - Estuary
Waihi Beach - at Three Mile Creek
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.
- Where there is an algal bloom in a lake, it seems unlikely that there is any risk from eating the flesh of trout but it’s very important to remove the gut and liver and wash in clean water first. Do not take or consume trout that are found already dead. Shellfish and kōura (freshwater crayfish) should not be eaten as would likely present a risk to health.
Shellfish research report
What's in our shellfish?
Towards the end of 2006 Environment Bay of Plenty (now Bay of Plenty Regional Council), Tauranga City Council, Western Bay of Plenty District Council and Toi Te Ora Public Health 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 (now Ministry of Primary Industries) 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:
- Investigation into the microbiological quality of Bay of Plenty estuarine shellfish
- Joint Agency Research Report 2009
- Joint Agency Research Report Presentation
- FAQ on shellfish gathering and consumption
- Food safety for seafood gatherers
- Media Release 09 October 2007: Agencies joining to study shellfish quality in estuaries
- Media Release 26 May 2009: Report confirms shellfish risky to eat
For information about current health warnings regarding shellfish - click here