Northern Pacific Seastars
What is the Northern Pacific Seastar?
Not all the marine life residing in Port Phillip Bay is good for the environment. The Northern Pacific Seastar is a great example of this.
The Northern Pacific is an invasive species of starfish which was accidentally introduced into Port Phillip Bay in the 1990s, most likely in the ballast water of ships sailing between the shipping ports of Asia and the Port of Melbourne, and is now a common site in many areas of Port Phillip Bay, including along the foreshore of the City of Port Phillip.
There are now grave concerns about the impact that this starfish is having on our native marine biodiversity, mainly due to its predation on shellfish and other invertebrates that are so important to our local food chain.
Description
The Northern Pacific Seastar has 5 arms with pointed tips which are upturned at the end. They are mainly yellow but generally also have purple patches, particularly at the ends of their arms. They are covered in many small spines with jagged ends that are arranged irregularly along their arms.
The Northern Pacific Seastar is capable of increasing in diameter by 8 cm per year, and can reach sizes of up to 50 cm in diameter when fully grown.
Habitat
These seastars like living in coastal water which is not exposed to high wave action, such as:
- estuaries and in deep water,
- soft sediment and reefs frrom intertidal to depths of up to 200 meters,
- around disturbed habitats such as wharfs and yacht clubs.
Why are Northern Pacific Seastars a problem?
With the ability to breed vary quickly - each female can produce up to 13 million eggs per year - it has few predators to reduce its population naturally. A few mature North Pacific Seastars can establish a new colony within months of reaching a new area.
There are concerns that the North Pacific Seastar will affect native marine biodiversity, mainly through predation on shellfish and other invertebrates that are important in the marine food chain.
The economic and environmental costs of eradication are prohibitively high, and chemical control is not an option for such a large body of water as Port Phillip Bay due to cost and damage to the marine ecosystem.
During the summer months, the North Pacific Seastar inhabits the cooler waters in the center of the Bay, but move closer to the shoreline as the water temperature cools; in Autumn the seastars move into the important seagrass beds surrounding St Kilda pier.
It is important to note that the Northern Pacific Seastar looks similar to certain native Australian seastars which reside in Port Phillip Bay, and removal of this starfish can only be done under licence from the Department of Sustainability and the Environment.
