Species have been moving about the planet using the ocean for millions of years. Until relatively recently, the winds and currents have mostly limited this process. But when humans took to the seas, a new way for species to travel around the globe came about.

Today, marine pests pose a significant risk to Victoria's marine environment and industries. Marine pests are highly invasive animals and plants which are not native to an area. They include a wide range of organisms, from microscopic algae to various species of sea stars, mussels, and crabs.

Marine species are most commonly introduced and spread by ballast water and biofouling. Ballast water is taken on board by vessels to maintain stability and trim. It can contain thousands of aquatic microbes, plants and animals which can spread across the globe when released. Vessel biofouling happens when marine plants and animals grow on the submerged parts of a vessel or infrastructure. 

Northern Pacific seastar (Asterias amurensis)
Image credit - Department of Agriculture, Water and the Environment (DAWE)
Asian shore crab (Hemigrapsus sanguineus)
Image credit - M. Connors
Commercial ship – offshore construction pre-clean
Image credit - Department of Agriculture, Water and the Environment (DAWE)

The northern Pacific seastar is a key established marine pest which found its way to Victoria via ballast water. It was first identified in Tasmania in 1986 and discovered in Port Phillip Bay in 1995. Each female northern Pacific seastar can produce between 5-20 million eggs. By the year 2000, more than 100 million of the species were estimated to be in Port Phillip Bay. The species eats a range of native animals with bivalves, like mussels and clams, being the preferred prey. 

The Asian shore crab is another key species that has entered Victoria from international waters. The first Australian detection of the species was from Mount Martha in October 2020. Originally from the waters around Japan, Russia, North China and Korea, the Asian shore crab has the potential to become a major pest. It could spread rapidly and may consume and outcompete our native species.

“Approximately 100 introduced marine species are now resident in Port Phillip Bay and can prey on – or outcompete – native species for space, food and light. Monitoring is critical to determine whether their range is expanding, with new incursions requiring rapid management responses”.
State of the Marine and Coastal Environment 2021 Report

The risk of introduction of marine pests via ballast water has been greatly reduced since the International Maritime Organisation’s Ballast Water Convention. Since 2017, it has required all international vessels to manage their ballast water. Yet, the introduction and spread of marine pests via biofouling remains a significant risk.

Help reduce the spread

Members of the community have a strong role to play in helping reduce the spread of marine pests and in protecting Victoria’s marine environment. Moving vessels and marine equipment from areas with marine pests to new locations can significantly increase the risk of spread. Vessel owners can help stop the spread of marine pests by always remembering to check, clean and dry.

  • Check your vessel and equipment for any attached animals and plants – remove them. Do not return marine pests to the water. 
  • Clean your vessel and equipment after use with freshwater. 
  • Dry your vessel and equipment thoroughly before moving to a new location.

The Victorian Government's Department of Jobs, Precincts and Regions is working closely with other Australian jurisdictions to reduce the risk of marine pest introduction and spread.

If you suspect you have seen a marine pest you can report the species via www.vic.gov.au/marine-pests or email reports to marine.pests@agriculture.vic.gov.au.

More information