Shellfish are a high-risk food because they may grow in contaminated (unsafe) water where they filter and accumulate biotoxins, bacteria, viruses, and chemicals from their surroundings. They are often eaten without being cooked. People who eat contaminated seafood can become seriously ill.
Shellfish and seawater samples around New Zealand are regularly tested to ensure they are not contaminated with biotoxins, and public warnings are issued when shellfish are not safe to eat. Biotoxins are toxins or poisons produced by algae that live in seawater and can ‘bloom’ or massively increase, when conditions are favourable.
Auckland Regional Public Health Service advises people not to eat shellfish gathered from urban areas because of the risk from illegally dumped contaminants, animal waste, road runoff, industrial discharges, leaching from buried materials and sewage overflows.
Our recommendations are:
Cooking shellfish at boiling point for several minutes will destroy most harmful bacteria and viruses, but not biotoxins or chemicals. Shellfish eaten undercooked or raw will still be risky to eat.
There are four main kinds of toxic shellfish poisoning. The chemicals that cause toxic shellfish poisoning are produced by certain species of algae and released into the shellfish when they filter large numbers of algae as food.
The most common and dangerous of these types of toxic shellfish poisoning is called paralytic shellfish poisoning. The symptoms of paralytic shellfish poisoning include:
Symptoms usually occur within 12 hours of eating the contaminated shellfish.
If you get sick after eating shellfish:
ARPHS will investigate cases of toxic shellfish poisoning, liaise with other agencies and issue public warnings, as appropriate to the nature and scale of the incident.
The Ministry for Primary Industries (MPI) tests shellfish and seawater samples regularly to check if they are contaminated with biotoxins. If marine biotoxin levels in shellfish are found to be unsafe, MPI advises the public.
General questions on environments at a particular beach can be directed to Auckland Council’s environmental health officers for the particular area (09) 3010101. There may also be related information on the Safeswim website.
Last updated 23.11.2018