Over 12,000 marine animals and plants live in Victoria's marine waters - many more than most comparable areas in the world. One of the biggest threats to Victoria's array of marine native plants and animals and to marine industries is introduced pest species.
What are marine pests and what do they look like?
Marine pests come in all shapes and sizes, from microscopic algae and larvae that can't be easily seen in the water column, to fish, seastars, molluscs and aquatic plants. At least 250 marine species are known to have been introduced to Australia's marine waters. Over 100 species are known to have been introduced to Port Phillip Bay.
Not every introduced species will become a pest. A pest species will feed on or compete with native species for food or shelter to the detriment of biodiversity or commercial assets in that area. They usually breed quickly and produce large numbers of offspring which often gives them a competitive advantage over indigenous species.
Pests can seriously affect habitats, food chains, the ecosystem and our enjoyment of the marine environment. Some marine pests are also a risk to human health and affect the social and economic benefits provided by the marine environment including aquaculture, recreational and commercial fishing and domestic and international shipping.
If you suspect you have seen a pest, please contact DEPI and 'report a pest'
For more information on marine pest species visit
To find out which pests are known to be in your area please see the
Marine pests in Victorian waters
Pacific Oyster incursion: Western Port and Wilsons Promontory National Park at Tidal River
The Department of Environment and Primary Industries was recently contacted by members of the community with reports of potential Pacific oysters present in small numbers in Western Port and Tidal River, Wilsons Promontory. This follows other reports in recent years of small numbers of Pacific oysters in Western Port.
Pacific oysters are a marine pest species in Victoria. They are highly invasive and can cause significant damage to the environment values and recreational use of affected areas, such as boat ramps.
After these reports were confirmed, DEPI set-up a working group with Parks Victoria (PV) and the Environment Protection Authority (EPA) to understand the extent and significance of the incursion.
An independent assessment will soon be carried out to identify environmental, social and economic impacts of this incursion to Victoria. It will be used to inform any further management responses.
Western Port and Wilsons Promontory National Park include areas of high conservation value. They include Ramsar wetland sites and Marine National Parks. The Victorian Government is committed to protecting these areas.
Surveys completed recently indicate that there are low numbers of Pacific oysters in Western Port across several locations. Surveys at Wilsons Promontory National Park found no other populations, indicating that Pacific oysters appear to be confined to the Tidal River area.
The EPA has advised the shipping industry of changes to their ballast water management requirements as a result of the positive presence of Pacific oysters in Western Port.
EPA's domestic ballast water system is the first of its kind protecting Victorian waters from marine pests sourced from other ports in Australia. No other state in Australia has similar measures in place.
|Northern Pacific Sea Star*, A sterias amurensis, is distinctive from native sea stars because it has five arms that taper into pointed, upturned tips. Colour on the top and sides of the arms ranges from a uniform pale yellow with purple arm tips to mottled yellow/purple. The underside of the arms and central disc are a uniform yellow.|
|European Fan Worm*, Sabella spallanzanii, is a large tube dwelling worm, up to 400mm long. It has a two layered crown of feeding tentacles which can vary in colour from a uniform dull white to brightly banded with stripes of orange, purple and white One layer of tentacles is distinctly spiralled.|
|Japanese Sea Weed * or Wakame, Undaria pinnatifida, is a brown seaweed up to 1-3 metres long. It is an annual species with two separate life stages. The microscopic stage (the gametophyte), present during winter, is rarely seen. The macroscopic stage (the sporophyte), present from late winter to early summer, is golden-brown in colour. The lighter coloured stipe has small pinnae at the top and during the reproductive season, a distinctive convoluted sporophyll at the base.|
* Species descriptions from the NIMPIS website
* Photos: CSIRO
How are marine pests spread?
Natural barriers including temperatures, currents or salinity gradients generally restrict the movement of marine species. However, there are two main ways that aquatic species can overcome these barriers and be spread to new locations:
- Natural range expansions - Pest species are masters of relocation. They can attach to a drifting object which can take them many kilometers away into previously uninvaded areas. Large environmental changes such as variations in nutrients, temperature or salinity can allow pest and native species to expand their range or relocate to a new area.
- Human related introductions - Activities around the globe including international shipping, aquaculture or boating provide 'vectors' that help aquatic species relocate. After being introduced, domestic activities including recreational boating can unknowingly spread species.
Australian waters are particularly susceptible to introduced species because we rely so heavily on the global shipping trade and because there are many small boats using our waters. With more small boats being used each year, care is needed to ensure that marine pests are not introduced and spread.
What is the solution?
"Prevention rather than cure" is the best approach when it comes to managing marine pests. Stopping pests being introduced to Australia and then from one location to another is far more effective than trying to deal with them after they have established. Eradication should not be relied on, as it is only feasible under specific circumstances.
See case study on eradication efforts in Anderson's Inlet.
Read more information on managing the impact of marine pests.