Marine Pests

Marine pests are highly invasive non-native animals and plants that cause significant damage to the health of native marine ecosystems. Marine pests are known to reproduce quickly and once established, often compete with and outgrow native species which can have a large impact on our unique marine environment.  Many of the plants and animals in the southern waters of Australia are native to our waters so taking care of the marine ecosystem and controlling potential threats is of the utmost importance.

The most effective way to control the spread of marine pests is to stop their introduction into new areas as their total eradication once established is very rare. While marine pests do spread naturally through rapid growth, people also help to spread pests as well through moving their vessels between different waters. All water users including fishers and boaters can play their part to stop the spread of marine pests by reporting suspected sightings and practicing good vessel hygiene.

If you do see a suspected marine pest, it is very important that you do not collect or remove the suspected pest as some pests can easily be mistaken for native species. Suspected sightings of marine pests outside of their known distribution should be made immediately to [email protected] or call 136 186.

Reported sightings of marine pests made to Park Victoria should include:

  • Photograph of the marine pest including a scale to show the size of the pest (for example, a coin or pen)
  • Location of sighting  including specifics such as GPS coordinates or markings on a map where possible)
  • Date and time of sighting
  • Type of sighting (for example it was seen from shore, on the seafloor, or on an anchor)
  • Contact details to follow up further details regarding the sighting

Use the Check. Clean. Dry. method to ensure good vessel hygiene which can help prevent the spread of marine pests.

Check. Clean. Dry

Moving boats and other vessels from waters with marine pests to new locations can increase the risk of spreading the marine pests.

All users of the marine environment have a role to play to avoid spreading the pest to other locations. Parks Victoria have suggested using good vessel hygiene through the โ€˜Clean. Check. Dryโ€™ method.

Good vessel hygiene through the โ€˜Clean, Check, Dryโ€™ method means:
1.        Check any equipment and vessels that have been in marine waters for pests
2.        Clean them in freshwater
3.        Dry the equipment before moving to a new marine location.

Other tips to help prevent the spread of marine pests:

  • Use fresh water to throughly wash down boats, vessels, fishing gear, wetsuits, water toys and other marine equipment after use.
  • Dry boats, vessels and other marine equipment throughly before moving to other locations.
  • When moving boats and marine equipment from areas known to have marine pests, particularly Port Phillip Bay, be vigilant in using the ‘clean, check, dry’ method before

Download Parks Victoria’s ‘Check. Clean. Dry’ handout for more information.

Some of the most common marine pests in Victoria include:

Japanese Kelp/ Wakame (Undaria pinnatifida)

Japanese kelp is a marine algae and a highly invasive marine pest. It negatively impacts our fish habitat where it is introduced, out-competes our native species and creates a dense seaweed forest in previously open areas.

In Victoria, Japanese kelp is already present in Port Phillip Bay, Apollo Bay and Port Welshpool. The complete eradication of the pest from these areas is unlikely as it has spreading within the area for some time, however, other areas are at risk of having the algae introduced.

It is important to prevent Japanese kelp from spreading to other areas as it is generally spread via the hulls of vessels travelling between areas. Marine pests are often microscopic so many boaters do not release they are transporting them via their boats and equipment.

Identification features of Japanese Kelp:

  • Frilly sporophyll, a leaf that grows spores, near the base of mature plants from early winter until late summer
  •  Brown in colour, can grow up to 3m long
  • Thick vein that runs down the middle of mature plants

Northern Pacific Seastar (Asterias amurensis)

A highly voracious predator, Northern Pacific Seastar, feeds on a wide variety of native marine species.  The Northern Pacific Seastar is prevalent in Port Phillip Bay.

Identification features of the Northern Pacific Seastar:

  • Five broad arms with pointed tips that are often upturned
  • Upper surface colour can vary from yellow to purple, while underside is consistently yellow
  • Irregularly arranged pointed spines on upper surface of arms
  • Up to 50cm in diameter
Photo by John Lewis

Pacific Oyster (Crassostrea gigas)

Pacific oysters are known to alter habitats and overgrowing and competing with native species. The Pacific oyster is a known pest in Western Port.

Identification features of the Pacific oyster:

  • Outer and interior shell is white-purple in colour
  • Can grow up to 15-20cm
  • The shell is sharp with jagged edges with large, irregular, rounded, radical folds.
  • One valve is usually entirely cemented on the rock surface

*Pacific oyster has also been seen in Port Phillip, Tidal River, Corner Inlet and Nooramunga Marine and Coastal Park however it is not considered a pest in the locations.

Photo by Jan Carey

Green Shore Crab (Carcinus maenas)

Green shore crabs are known to be aggressive predators with broad diets. They often compete with native crab populations for food and habitat.

The green shore crab is prevalent across Victoria including Gippsland, Port Phillip Bay and Western Port.

Identification features of the green shore crab:

  • Can grow up to 8cm in diameter
  • Green coloured on the upper surface
  • The colour of the under surface varies and can be red, orange or green
  • Broad, triangular carapace that is structured on top
  • Four distinct notches in the carapace on both sides of the eyes
  • The last pair of legs are pointed and cannot be used for swimming
Photo by Museum Victoria

European Fanworm (Sabella spallannzanii)

European Fanworm can form dense colonies while competing with native filter feeding organisms for food and space. European Fanworm is well established in Port Phillip Bay and in some other local ports. It is yet to be observed in Western Port.

Identification features of the European Fanworm:

  • Large tube dwelling worm with a crown of feeding tentacles formed in two layers. One layer is distinctly spiralled
  • The fan colour comprises of bands of orange, purple/brown and white
  • A long leathery tube that can grow over 30cm
  • If the worm is disturbed, the crown can be completely withdrawn
Photo by Mark Rodrigue (Parks Victoria)

New Zealand Screw Shell (Maoricolpus roseus)

The New Zealand Screw Shell compete with native filter feeders for food. They prevent native screw shells from inhibiting an area by densely covering the sea floor with five and dead shells. New Zealand Screw Shells are known to inhibit coastal areas of Eastern Victoria including Corner Inlet and west of Wilson’s Promontory in Waratah Bay and Shallow Inlet. It is currently not known to inhibit Port Phillip Bay or Western Port.

Identification features of the New Zealand Screw Shell:

  • Animal body is yellow-green in colour
  • The shell grows up to 9cm long and 2.5 cm wide, with up to 18 whorls (spirals). Shell surface is closely but irregularly spiralled
  • The shell is variable in colour. Ranges from yellowish to reddish or purple-brown with a faintly marbled pattern or dark brown streaks on the shell surface
Photo by Des Beechley

Aquarium Caulerpa (Caulerpa taxifolia)

Aquarium Caulerpa is a highly invasive plant that can cover thousands of hectares and stop other algae from growing. It can smother other algal species, seagrasses and immobile invertebrate communities such as mussels. While it is not yet present in Victoria outside of aquariums, it is a major potential threat. It is well established in New South Wales and South Australia.

Identification features of Aquarium Caulerpa:

  • Light green upright leaf-like, flat fronds with a midrib. The fronds grow from a horizontal branch
  • Little branches extend out from the midrib of the fronds, in an opposite arrangement
  • The fronds can grow up to 60cm in deep water and are usually 3-15cm long in shallow waters
  • The fronds are between 6 and 8 mm in diameter

Red Algae (Grateloupia turuturu)

Due to the large size of red algae, it can cover native algae on reefs. As it rapidly grows through the summer then dies back in winter, it changes the availability of food for grazing species such as snails. Red algae is widespread in northern Port Phillip Bay.

Identification features of red algae:

  • Red algae can grow up to 3m in length in summer
  • Red algae is red in colour with thin blades
  • Often features smaller bladelets at the base of the plant
  • It is slippery to touch
Photo by Parks Victoria

Dead Man’s Fingers (Codium fragile ssp. fragile)

Dead man’s fingers can grow rapidly, it can regenerate from a broken branch meaning it easily transfers between areas. As it grows, dead man’s fingers can out shade native algae. It is widespread in Port Phillip Bay, known to inhibit San Remo and Newhaven in Western Port.

Identification features of dead man’s fingers:

  • It is a green spongey seaweed with ‘finger-like’ branches
  • It attaches itself to rocky reefs and other hard surfaces

Dead man’s fingers looks very close to native Codium. Therefore, it can only be confirmed as dead man’s fingers by checking a sample under a microscope.

This image has an empty alt attribute; its file name is Codium-fragile-subs-fragile-Jan-Carey.jpg
Photo by Jan Carey

Asian Date Mussel (Musculista senhousia)

Asian date mussels can change the natural sea floor habitat by forming a dense mat which can impact the species that live in the area. They favour lying vertically under soft sediment with the end slightly protruding. They are found in Port Phillip Bay and Western Port, including Yaringa and French Island Marine National Parks. Some have also been observed in the Gippsland Lakes.

Identification features of Asian date mussel:

  • Shell ranges from olive green to brown in colour with zig zag markings or radial lines
  • The shell can grow up to 3cm, but is most commonly observed between 1-2.5 cm
  • The shell can be crushed easily
Photo by Mark Norman

Cord Grass (Spartina angelic and Spartina x townsendii sp)

Cord grass is an aggressive plat that can cover thousands of hectares. It can be spread easily by seeds and plant parts. It can outgrow and invade other native grasses in an area. It is found in Lake Connewarre in Barwon Heads, and at the mouth of the Bass River and in drain outlets near Tooradin in Western Port. It is widespread in South Gippsland including Andersons Inlet, Cornet Inlet and Nooramunga Marine and Coastal Park.

Identification features of cord grass:

  • Light green grass with long, smooth and hairless leaves
  • Leaf blades can be either flat or folded and end with a fine hard point
  • Leaves grow up to 45cm long and 1.5cm wide
  • A 2-3 mm long collar of desert hairs forms at the base of the leaves
  • Initially the plant will grow in clumps but can spread into extensive swards

Information sourced via the Parks Victoria’s Marine pests in Victoria’ reference guide.

Visit the Parks Victoria Marine Pests website for more information.

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