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Northern Pacific Seastars invade the Maribyrnong River

Monday 6 May, 2019

Reduced rainfall allows pest to proliferate

Reduced rainfall over the past months have led to the Northern Pacific Sea Star being sighted upstream in the Maribyrnong River in numbers not previously seen in the area.

The lower Maribyrnong River is an estuary environment with seawater extending up the river. Seawater is naturally denser then freshwater so it gravitates lower on the river floor. Reduced rainfalls have potentially increased river salinity further upstream, allowing the seastars to proliferate in numbers not seen in this area previously.

The Northern Pacific Seastar, originating in Japan, arrived into Port Phillip Bay via international cargo ships in the mid-1990s and has since become a dominant species, owing to its high reproductive capacity (each female can lay between 15-20 million eggs) and greedy appetite targeting native species.

Once established in a marine area, Northern Pacific Seastars are nearly impossible to eradicate owning to their high reproductive rates and difficult accessibility of the estuary floor.

Marine pests like the Northern Pacific Seastar are easily spread on boats and marine equipment. To help stop the spread of these animals from the Maribyrnong River and Port Phillip Bay into unaffected areas Parks Victoria urges marine users to:

  • Check their boats, trailers and other gear for visible pests and remove them.
  • Clean boats and gear with freshwater which will kill eggs, spores and smaller pests
  • Dry boats and marine equipment thoroughly before moving to new locations – particularly outside Port Phillip Bay

More information about marine pests and how their spread can be prevented, is available on Parks Victoria's website and people are encouraged to call 136 186 to report any sightings of marine pests.

Quotes attributable to Mark Norman, Chief Conservation Scientist - Parks Victoria:

“Victoria’s marine waters have incredible biodiversity, supporting more than 12,000 species of plants and animals, 90 per cent of which are found nowhere else in the world, it’s vital we protect these natural assets.”

“Marine pests are highly invasive animals and plants, usually from other parts of the world that have become established in Victoria and cause significant harm to the health of marine ecosystems.”

Media enquiries
David Clay
0497 555 192

Parks Victoria media centre