The invasive Northern Pacific seastar has been rediscovered in highly protected waters off south-east Victoria despite efforts to eradicate the marine pest four years ago.
The “highly voracious predator” was found in Wilsons Promontory National Park by ranger Chris Hayward when he was diving under a footbridge in Tidal River last month.
Mark Rodrigue from Parks Victoria said the seastars bred quickly and could spread rapidly.
“These things are predatory, they live on the bottom of the sea,” he told ABC Radio Melbourne.
“They feed on quite a range of different species, including some of the animals that humans tend to value highly, things like fish.
“You’ve got a species that basically interferes with some of the natural cycles of the food chains that should be there.
“We’re very concerned that if you get a second population of these animals in other parts of Victoria they provide a stepping stone for invasion of further parts of the coastline.”
Wilsons Prom is well known to divers for its stunning marine life; home to a range of fish, molluscs and corals.
Several seastars were found at Tidal River in 2012 and Parks Victoria divers removed them by hand over the next year.
The pests are found in Port Phillip Bay but have been eradicated in other coastal areas at San Remo and Inverlock.
They can grow up to 50 centimetres in diameter and have five arms with pointed tips which vary in colour from yellow to purple.
The seastars are native to waters in the northern Pacific Ocean around Korea, Japan and eastern China.
Mr Rodrigue said the seastars were able to find a home in Victorian coastal areas as water temperatures were similar to their native habitat.
He said they most likely arrived in ballast water which ships carry for balance when they load and unload cargo.
“It’s a major problem worldwide, not only for seastars but for a whole range of other species that are now unfortunately in Port Philip Bay.”
Mr Rodrigue said people on boats needed to be aware of spreading the seastar’s larvae.
He urged people to wash gear with fresh water and make sure equipment was dry, especially those travelling from Port Phillip Bay to Wilsons Prom.
“This is going to be an ongoing problem and I think the important thing for all of us who use boats or who use the marine environment to understand that while these are very prolific breeders, it’s humans that can actually play an important role in spreading of these things.”
Parks Victoria said it would search Tidal River to determine how many seastars had infested the area.