"If the gut is not removed, its contents could contaminate the meat during the cooking process."
Snapper, gurnard and tarakihi are not affected by the algae and are still safe to eat.
Commercially harvested shellfish sold in shops and supermarkets are subject to strict water and flesh monitoring programmes by MPI to ensure they are safe to eat.
In June last year, locals were warned not to consume shellfish found between Whareongaonga and Mohaka River because of dangerous toxins.
Symptoms typically appear between 10 minutes and three hours after ingestion, and may include numbness and a tingling/prickly feeling around the mouth, difficulty swallowing or breathing, dizziness, headache, nausea, vomiting, diarrhoea, paralysis, respiratory failure and, in severe cases, death.
-If anyone becomes ill after eating shellfish from an area where a public health warning has been issued, phone Healthline on 0800 61 11 16 or seek medical attention immediately.