Duck hunters in Canterbury are being warned to avoid contact with an algae found in three of the region's lakes.
Hunters have taken to their maimais around the country for the start of the shooting season this weekend.
Canterbury District Health Board says Lake Forsyth, Lake Rotorua and Lake Roundabout are in bloom with unsafe levels of blue-green algae, or planktonic cyanobacteria.
Medical officer of health Alistair Humphrey said the algae can cause irritation and allergy symptoms in people and can kill animals.
Dr Humphrey says ducks can still be cooked and eaten if their gut has been removed, but people should wash their hands thoroughly after handling them.