4.4 IMPACTS IN AUSTRALIA
A large proportion of the Australian coastline (80-90%) has not been surveyed for possible introductions of marine organisms, thus the actual number of introduced species in Australian waters is not known136 The CSIRO has compiled a list of 172 exotic marine species in Australia137 however, it is believed that there are far more than are currently recognised138
The Agricultural and Resource Management Council of Australia and New Zealand (ARMCANZ) has nominated four 'target' species as being of particular concern due to the impacts they are already having in Australia, and because of the risk of translocation to new Australian waters. In addition to these, Walters nominated a further three species which are important from a Victorian perspective139 and the Committee adds the recently recorded Codium fragile tomentosoides (Codium) at Corner Inlet and in Port Phillip Bay. The Committee therefore nominates the following eight organisms as being of particular concern to Victoria.
1) Asterias amurensis (northern Pacific sea star)
2) Toxic dinoflagellate species.
3) Undaria pinnatifida (Japanese kelp)
4) Sabella spallanzanii (Sabella)
5) Carcinus maenas (European shore crab)
6) Musculista senhousia (Asian mussel)
7) Corbula gibba (Corbula)
8) Codium fragile tomentosoides (Codium)This Report now examines more closely the above introduced marine organisms, and their distribution in Australia.
4.4.1 Asterias amurensis (northern Pacific sea star)
The northern Pacific sea star (Plate 3) is a five armed sea star which typically inhabits waters which are cold-temperate, sub-littoral and shallow140 Its natural distribution extends over the northern coast of China, the coasts of Korea and Japan, and along the Russian coast to the Bering Strait141 It is thought that the sea star was first introduced into Australia 20 to 30 years ago, arriving in the Derwent River in Tasmania via ships' ballast water142 or on hulls143 It was not recognised in Tasmania, however, until 1993144
In Tasmania, the sea star has established populations in the Derwent estuary (Port of Hobart), D'Entrecasteaux Channel, Huon Estuary, parts of Storm Bay, Frederick Henry Bay, Triabunna and Mercury Passage and in Great Oyster Bay145The extent and the nature of the impacts of the sea star seem to vary regionally; in some areas it remains consistently present in small numbers, whereas the population explodes periodically in other areas causing havoc in local fishing and mariculture operations146 While no major economic impacts have been reported by commercial fisheries in Tasmania to date, there is potential for future losses due to displacement of native species147 In the Derwent river alone, it is estimated that there are about 28 million sea stars which have led to the virtual elimination of bivalve molluscs148
PLATE 3
Asterias amurensis (Northern Pacific sea star)
Source: CRIMP - CSIRO
The sea star is a voracious predator of shellfish and is also known to prey on sponges, crustaceans, polychaetes and fish149 In fact, the sea star will consume almost any animal tissue it can capture150 A single specimen produces 10-20 million eggs each year for about 5 years151 The eggs and larvae are planktonic and drift in the ocean for up to two months, allowing them to be dispersed great distances by ocean currents. This also means that they are very susceptible to uptake by ballasting ships. Adult sea stars may also be transported by attaching to fouling encrustations on ships' hulls152
The sea star poses a significant threat to the integrity of Australian marine ecosystems, aquaculture, wild fisheries and biodiversity. Over the past year, four sea stars have been found in Port Phillip Bay in separate instances, but it is not known whether there are established populations in the Bay. It has been predicted that the sea star has the potential to spread along Australian eastern coasts as far north as Sydney, and possibly towards Western Australia153
4.4.2 Toxic dinoflagellates
A number of ports in New South Wales, Victoria, Tasmania, South Australia and Western Australia are known to be infected by one or more species of toxic dinoflagellates154 Although it is difficult to determine the origin of these species, (only Gymnodinium catenatum has conclusively been found to be an exotic species introduced via ballast water), it is thought that a number of species have been introduced via ballast water155 In 1992, Hallegraeff and Bolch tested the ballast of 340 ships entering 18 Australian ports and found dinoflagellate cysts in vessels entering all ports sampled156
Toxic algal blooms have periodically led to the closure of shellfish farms in Tasmania, sometimes for periods of up to 6 months, and have required the establishment of a monitoring program to determine toxin levels in shellfish157
A number of toxic dinoflagellate species, including Alexandrium sp. and Gymnodinium sp., are found in Victorian waters158 Water sampling conducted in 1992 at Lorne, Apollo Bay, Port Campbell, Warrnambool, Port Fairy and Portland indicated the presence of Paralytic Shellfish Poisoning (PSP) toxins at all sites. In the winter of that year, bans were placed on shellfish from Lorne due to PSP contamination159
Since 1987, the Fisheries Branch of DNRE has conducted a shellfish biotoxin monitoring program in Victoria160 The program's aims are to ensure commercial shellfish meet public health standards, to maintain the viability of the industry, and to protect recreational harvesters from shellfish poisoning161 In Port Phillip Bay, biotoxin monitoring is currently undertaken every two weeks162
The Gippsland Lakes are particularly susceptible to algal blooms because of their high nutrient levels. The Tamboon Inlet has experienced contaminated wildstock mussels caused by Neurotoxic Shellfish Poisoning (NSP). As a consequence, there have been many reports of people falling ill, and warning signs have been erected163 This could adversely effect tourism and recreational activities in the region.
The Japanese or brown kelp is a native species of north-east Asia, Japan and China (Plate 4). The kelp was first recorded in Australia at Rheban on Tasmania's east coast in 1988164 and is thought to have been introduced to Tasmania in the ballast water and/or hulls of woodchip vessels165
PLATE 4
Undaria pinnatifida (Japanese kelp)
Source: CRIMP - CSIROJapanese kelp has spread gradually to more than 50 km of the Tasmanian coastline and is now found at Triabunna, Great Oyster Bay, Coles Bay, Blackman Bay and Maria Island166 This spread is attributed mainly to ocean currents and transfer via vessel hulls. Recent evidence suggests that it is also being spread by commercial fishing boats through plants being caught in nets167
In Coles Bay, the kelp has been found growing profusely on mussel culture lines168 It also grows readily on ropes and cages causing fouling in marine farms169 In 1994, it was estimated that there was a standing crop of 400 tonnes of kelp on the Tasmanian East Coast,170where it has displaced native species such as rock lobster, abalone and oysters.
In July 1996 the kelp was identified in Port Phillip Bay. It has been predicted that the alga has the potential to establish on the southern Australian mainland from Cape Leeuwin (WA) to Wollongong (NSW) 171
Japanese kelp poses a major threat to endemic algal communities because of its rapid growth and capacity to exclude native species by overgrowing172 In addition, species of fungi which can be pathogenic to native algae and seagrasses are known to have been transferred with introduced algae173
In Japan, the kelp (known as "wakame") is an important food crop and there may be potential for commercial harvesting in Australia174
4.4.4 Sabella spallanzanii (Sabella worm)
The Sabella worm, also known as the giant Mediterranean fan worm, is native to the Mediterranean Sea and the east coast of the Atlantic as far north as the English Channel. It grows to a length of up to 40cm, encased in a tough, leathery tube from which long bristles protrude (Plate 5). These bristles are covered in cilia which create currents to draw in suspended food particles175 The worm may be found from just below the surface of the water to depths of 30m176 It attaches to hard surfaces such as jetty pylons or boat hulls, or to shell fragments or rocks within soft benthic sediment177
It is thought that the worm was introduced into Australia from the Mediterranean either as larvae in ships' ballast water or as a fouling organism on hulls178 The spread of the Sabella worm around Australia can certainly be attributed to the latter. The similarity of populations within Australian ports indicates that the worm has spread within Australia from a single introduction179 Its current distribution includes Port Phillip Bay, the Coburn Sound and Albany in Western Australia, and the Gulf of St Vincent in South Australia180
PLATE 5
Sabella spallanzanii (Sabella worm)
Source: CRIMP - CSIROThe Sabella worm is of major concern in Port Phillip Bay because of its recent rapid spread and lack of natural predators. It is believed that fish will not feed on the worm due to high levels of vanadium in the worms' feeding crowns181 Sabella tolerates a wide range of salinity levels and temperatures, and has a high rate of reproduction. Females can produce in the order of 1 million eggs at a time, representing half their body mass182
The Sabella worm is thought to have been introduced to Port Phillip Bay ten to fifteen years ago183 Although it has exhibited fluctuations in population density184 the worm has expanded its range and now inhabits approximately 50% of the Bay, extending eastward from Corio Bay. It has created new 'reef like' habitats in the Bay and can be found in densities of up to 100 per square metre on the seabed185 The potential impacts of the worm in Port Phillip Bay are discussed in Section 4.5.
The European shore crab is native to Europe but has a wide distribution elsewhere. It is an aggressive and voracious predator, inhabiting intertidal and subtidal zones of sheltered shores186 No other crab is known to have such a broad diet range, high feeding rate and habitat diversity187
It is thought that the European shore crab came to Australia via Port Phillip Bay after 1856 on the hulls of ships188 It has also been suggested that the crab was deliberately introduced for its edibility189 In Victoria the crab can be found at various sheltered sections of the Victorian coastline, including Westernport Bay, Wilson's Promontory and Corner Inlet190 The distribution of the crab extends as far north as Narooma, New South Wales and west into South Australia, including Port Adelaide and Port Stanvac. A single specimen has been recorded in Western Australia and the crab has recently been identified in a number of ports in Tasmania191
The European shore crab seems to have had little impact on aquaculture and wild fisheries operations in Australia to date192 although there are concerns about its potential effects based on reports of its impact in North America where it has devastated the soft shell clam industry on the US east coast193 The crab has also been introduced into South Africa where it threatens several native species194
It has been suggested that the crab may present an exploitable marine resource in Australia for the aquaculture industry195
4.4.6 Musculista senhousia (Asian Mussel)
The Asian mussel is indigenous to eastern Asia; its natural distribution extends from the western Pacific coast of Siberia south to Singapore196
The mussel is a fouling organism which may have been transported to Australia via ships' hulls or in pipes or anchor wells, or as larvae in ballast water. It was first recorded in 1982 in the Swan River in Western Australia, and is now also in Fremantle and the Canning River197 It is thought to have been transferred to Victoria from Western Australia198 It was first recorded in Corio Bay in 1987, and it is now abundant in Port Phillip Bay199
The mussel occupies a wide variety of habitats from the intertidal zone down to depths of 20m and is an encrusting species on hard substrates. On soft substrates it forms 'nests' or mats which can radically alter the biota and movement of soft sediments200 Mussel colonies spread rapidly, out-competing native species for space, trapping finer sediment particles, and effectively producing mud flats with consequent major changes to the endemic fauna201 The mussel may occur at densities exceeding 3,300 per square metre202
The Asian mussel has a very high fecundity and can attain reproductive size in only nine months203
The Asian mussel has the potential to compete with native species for food and habitat, and may pose threats to mussel farms204 In Port Phillip Bay, the Asian mussel has established dense populations in shallow waters in Corio Bay205
4.4.7 Corbula gibba (Corbula)
Corbula, also known as the European clam, is a small, sedentary bivalve with a distinctive asymmetrical shell. Its natural range is from Norway to the Mediterranean206
In Australia, Corbula has been recorded in Port Phillip Bay207and the Port of Portland208 Corbula inhabits muddy, gravelly sand in shallow, sub-littoral zones to depths of about 140m209and competes with scallops and other local species for food. Since the 1960s, there have been insufficient numbers of scallops in central Port Phillip Bay to support commercial harvesting. This decline has been attributed to Corbula due to increased competition for food210 The Committee notes that the abundance of the Sabella worm in the Bay may also contribute to reduced availability of food for scallops.
Other impacts of Corbula on marine communities in Port Phillip Bay are not known, however a related species Potamocorbula amurensis has had devastating effects on native clam species since its introduction into San Francisco Bay in 1986211
A number of species of Codium are endemic to Australia. In the early 1990s a bloom of macroalgae at Corner Inlet in Victoria was identified as Codium fragile tasmanica, an Australian subspecies known for about sixty years, commonly referred to as Broccoli Weed212 In late 1996 the algae was re-assessed and identified as Codium fragile tomentosoides213 a species native to Japan and the north west Pacific which has been introduced to the United States, New Zealand, the Mediterranean and the United Kingdom214 This was the first record of Codium in Australia. Codium does not appear to have spread to the adjacent Nooramunga Marine Reserve215 however, it has since been found in Port Phillip Bay, growing amongst another recently introduced exotic species, Japanese kelp216
The algae is commonly dispersed as a fouling organism on ship hulls, by currents and by nets and wells of fishing vessels217 There is a commercial fishing industry which alternates between the Gippsland Lakes, Tasmania and Port Phillip Bay, and until recently, Bass Strait trading vessels visited Port Welshpool, Corner Inlet. In addition, a number of these commercial vessels which visit the Inlet service oil rigs in Bass Strait also operate internationally.
Codium displaces native benthic flora and fauna, fouls shellfish beds, competes with seagrass and may have significant impacts on fisheries218 The algae is listed by the Australian Quarantine and Inspection Service (AQIS) as a target exotic species of particular concern because of its invasive potential219Corner Inlet is mainly within the Corner Inlet and Nooramunga Marine and Coastal Parks, and the southern shoreline forms part of Wilsons Promontory National Park. The Inlet is a high value wetland of international significance, being noted for its high productivity, geomorphology and significant flora and fauna. The Inlet, which contains the most extensive intertidal mudflat system in Australia, is listed under the Ramsar Convention and is registered on the National Estate. Twenty two birds listed under the Japan Australia Migratory Bird Agreement (JAMBA) and seventeen under the China Australia Migratory Bird Agreement (CAMBA) have been recorded in the Inlet220
