New Zealand's native whelk could be in danger from a new slippery Aussie invader.

Auckland Museum research associate Margaret Morley said the Australian dog whelk was first recorded by Niwa scientists and its population was "exploding" from Whangarei Harbour to Tamaki Estuary.

"It's only 8-9mm so it's very tiny but has just recently been found in huge numbers in Whangarei Harbour," Morley said.

According to marine biologist Dr John Walsby, the New Zealand native mud whelks have an amazing sense of smell.


They can track food from more than 10m using a special scent gland. They feed on sick or dead marine life by mincing up the flesh and sucking it through a feeding tube.

Population changes would affect marine biodiversity as the whelk is part of the diet of a range of bottom-feeding fish, such as snapper and tarakihi.

Morley said she would be studying the molluscs in Whangarei and was interested to hear from people who spotted them elsewhere.

"They like sheltered harbour areas or estuaries. They are predatory but they scavenge and eat dead cockles and things like that. We have our own native whelk and we hope there is enough food for all of them. The Australian one is smaller but it moves more quickly. It comes out of the sand and for a small thing it moves very quickly," she said.

Australian marine biologist Kirsten Benkendorff said she was keen to study the mollusc after finding another variety of the whelk had cancer-beating properties. Antibiotic agents found in the snails were very active against cancer cells and reduced the formation of tumours.