Lyla Lindsey
The Northern Pacific seastar (Asterias amurensis), native to the coasts of northern China, Korea, eastern Russia, Japan, and Alaska, is an invasive species in Australia. It was first seen in Tasmania in 1986 and has since spread to Victoria. The species is included in Australia's Priority Marine Pest List, owing to its impacts on aquaculture, commercial shellfish industries, and native species. The introduction of non-indigenous species like Asterias amurensis can act as vectors for new diseases, reduce biodiversity, and cause economic losses. This has led to efforts by the Australian government to prevent and manage the incursion of marine pests.
| Characteristics | Values |
|---|---|
| Common names | Northern Pacific seastar, Japanese common starfish, Japanese seastar, Japanese starfish, north Pacific seastar, purple-orange seastar, flatbottom seastar |
| Scientific name | Asterias amurensis |
| Native regions | Japan, northern China, Korea, eastern Russia, Alaska, the Aleutian Islands, British Columbia in Canada |
| Habitat | Shallow waters, estuaries, mud, sand, silt, rocky sheltered areas of intertidal zones, rocky reefs, depths up to 200m |
| Appearance | Small central disc, five arms with pointed tips, pale yellow to purple in colour |
| Size | Up to 50 cm in diameter |
| Diet | Prey on large bivalve molluscs |
| Predators | Predated by other species of starfish |
| Reproduction | Females release 10-25 million eggs per year, which are externally fertilised by sperm released by male sea stars |
| Impact on Australia | Introduced to southern Australia, especially Tasmania, causing damage to native species and the shellfish industry, listed as a pest species of national priority |
| Control measures | Sea star hunting days, physical removal |
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What You'll Learn
Larvae in ballast water
Asterias amurensis, commonly known as the Northern Pacific seastar, is a species of seastar native to the coasts of northern China, Korea, far eastern Russia, Japan, Alaska, the Aleutian Islands, and British Columbia in Canada. It is characterised by its five distinct arms that taper to pointed tips and its preference for shallow waters and estuaries.
The species has been introduced to non-native habitats, including southern Australia, where it is considered an invasive pest. The most likely mechanism for its introduction to Australia is the transport of free-swimming larvae in ballast water carried by ships. This is supported by the fact that A. amurensis was first reported in Tasmania in the 1980s, coinciding with the arrival of commercial vessels from regions where the species is native, such as Japan.
Ballast water is essential for ship stability and is pumped in and out of ballast tanks to maintain a safe water level and balance the ship's weight distribution. When ships take in ballast water in ports where A. amurensis is present, such as in Japan, they inadvertently suck in the free-swimming larvae of the species. As ships travel to other destinations, they release the ballast water, along with the larvae, into new ports.
In the case of Australia, the discharged ballast water containing A. amurensis larvae has led to the colonisation of various locations, including the Derwent Estuary, Port Phillip Bay, and Henderson Lagoon in Tasmania. The larvae metamorphose into juvenile sea stars, contributing to the spread of this invasive species in Australian waters. The introduction of A. amurensis through ballast water has had ecological and economic impacts, affecting native species and industries such as aquaculture and commercial shellfish operations.
To address the issue of invasive species, researchers have developed sensitive PCR-based methods to detect Asterias DNA in ballast water and environmental samples. These techniques are crucial for early detection and assessing the risk of further introductions to uninvaded ecosystems. Additionally, physical removal of A. amurensis through "sea star hunting days" has been deemed effective and politically attractive compared to chemical or biological control processes.
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Economic impacts
Asterias amurensis, also known as the Northern Pacific seastar, is an invasive species in Australia. It was first seen in Tasmanian coastal waters in 1986 and has since spread to Victoria. The likely mechanism of its introduction to Australia is the transport of free-swimming larvae in ballast water for ships.
The economic impacts of Asterias amurensis in Australia are significant and far-reaching. As an invasive species, it has been listed as a pest of national priority due to its detrimental effects on aquaculture and commercial shellfish industries. The introduction of non-indigenous species can cause major economic losses, and Asterias amurensis is no exception. Its presence in Australia has resulted in the following economic consequences:
- Negative impact on the mariculture industry: In Japan, population outbreaks of Asterias amurensis have cost the mariculture industry millions of dollars in control measures and losses from predation. Similar impacts have been observed in Tasmania, where the species has affected mussels and oysters.
- Damage to commercial shellfish industries: Asterias amurensis preys on large bivalve molluscs, including scallops, mussels, and oysters. The decline in populations of these shellfish due to predation by Asterias amurensis has had economic repercussions for commercial shellfish industries in Australia.
- Disruption to marine ecosystems: The introduction of Asterias amurensis has altered marine ecosystems and reduced biodiversity. It competes with native species for resources and has been linked to the decline of the endemic endangered spotted handfish in Tasmania. Such disruptions can have far-reaching economic consequences for fisheries and tourism industries that depend on healthy marine ecosystems.
- Control and management costs: Controlling and managing invasive species can be costly. In Tasmania, several "sea star hunting days" have been organized to remove Asterias amurensis, and physical removal has been identified as the most effective and safe method compared to chemical or biological control processes. These control measures incur financial costs and require resources and labor.
- Impact on traditional medicine: In China, Asterias amurensis is considered useful in traditional medicine and is included in the Pharmacopoeia of the People's Republic of China. However, the economic impact of this on Australia is unclear.
The economic impacts of Asterias amurensis in Australia are ongoing and significant. The species' invasive nature, ability to adapt to new environments, and high reproductive rate (with female seastars capable of releasing 10-25 million eggs per year) contribute to its potential for massive population growth and subsequent economic damage. The Australian government and relevant industries continue to work on prevention and management strategies to mitigate the economic and ecological impacts of this invasive species.
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Native species damage
Asterias amurensis, also known as the Northern Pacific seastar, is a species native to the coasts of northern China, Korea, far eastern Russia, Japan, Alaska, the Aleutian Islands, and British Columbia in Canada. It is a predator that feeds on large bivalve molluscs, mussels, scallops, and clams, and can impact the abundance of juvenile bivalves.
The species was introduced to southern Australia, specifically Tasmania, in the 1980s, and has since spread to Victoria. It is considered an invasive species in Australia, causing damage to native species. The most likely mechanism of introduction is the transport of free-swimming larvae in ballast water for ships. The larvae are sucked into the ballast water in one port, such as those in Japan, and released in another, such as those in Tasmania, where they metamorphose into juvenile sea stars.
In Tasmania, the Northern Pacific seastar has been linked to the decline of the endemic endangered spotted handfish. It has also impacted mussels and oysters in the region. The species has been observed in a range of habitats, including estuaries, mud, sand, silt, rocky sheltered areas of intertidal zones, and even rocky reefs and bedrock.
Given the species' ability to establish large populations in new areas, its impact on native species in Tasmania, and its listing as an Australian pest species of national priority, prevention and control measures are crucial to stop it from spreading to other waters and causing further damage to native species.
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Control methods
The Northern Pacific seastar, Asterias amurensis, is an invasive species in Australia, causing damage to native species, especially in Tasmania. It was introduced to Tasmania in the 1980s and has since spread to Victoria. The most likely mechanism of its introduction is the transport of free-swimming larvae in ballast water for ships.
- Physical removal: This method has been estimated to be the most effective, safe, and politically attractive option when compared to chemical or biological control processes. Several "sea star hunting days" have been organized in Tasmania, resulting in the removal of several thousand sea stars.
- Chemical control processes: While considered a possible removal method, chemical control processes may be costly and controversial.
- Biological control processes: This method may also be costly and controversial, and it is not considered as safe or effective as physical removal.
- Vector control: The Australian and New Zealand Environment and Conservation Council (ANZECC) and the Ministerial Council on Forestry, Fisheries and Aquaculture (MCFFA) established the National Taskforce on the Prevention and Management of Marine Pest Incursions in 1999. The Taskforce recommended vector control as the best solution for managing marine pests, as eradication programs can be challenging and contentious.
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Introduction to Tasmania
Tasmania is an island state of Australia, located 240 kilometres (150 miles) south of the mainland, separated by the Bass Strait. It is Australia's smallest state by both size and population, with around 573,479 residents as of June 2023, 40% of whom live in the Greater Hobart area. The main island of Tasmania is the 26th largest in the world, accompanied by 1000 surrounding islands.
Tasmania was first inhabited by Aboriginal peoples, who today generally identify as Palawa or Pakana. The Aboriginal Tasmanians are believed to have become isolated from mainland groups around 11,700 years ago due to rising sea levels. The Aboriginal population was estimated to be between 3,000 and 7,000 when Europeans permanently settled the island as a penal colony of the British Empire in 1803. Within three decades, this number declined drastically due to violent conflict and the spread of infectious diseases.
Tasmania is known for its wild and dramatic landscapes, pristine white beaches, and excellent food and wine. The island is a hiker's paradise, with numerous wilderness trails that wind through deserted forests and 19 national parks, which make up 21% of the state's land area. The coastlines feature serene turquoise bays and rugged, rocky shores facing the choppy seas. Tasmania's many microclimates allow for the growth or harvest of a diverse range of produce, from dairy to seafood, and its clear waters are abundant in seafood. The island is also a significant wine-producing region, with wine routes worth exploring.
Tasmania has the second smallest economy among Australian states and territories, with its principal industries being tourism, agriculture, aquaculture, education, and healthcare. The state has gained recognition as a significant destination for eco-tourism, with about 42% of its land area protected in some form of reserve.
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Frequently asked questions
Asterias amurensis, also known as the Northern Pacific Sea Star, is believed to have been introduced to Australia through the transport of free-swimming larvae in ballast water for ships. The larvae are sucked into the ballast water in one port, such as in Japan, and then released in another port, such as Tasmania, where they metamorphose into juvenile sea stars.
No, Asterias amurensis is not native to Australia. It is an invasive species in Australia, causing damage to native species, especially in Tasmania. It is included in Australia's Priority Marine Pest List.
The economic effects of Asterias amurensis in Australia are still being evaluated. However, it is believed that if the species continues to spread, it could compromise the soft sediment communities along the Australian coast. There have already been negative impacts on several fisheries, with an estimated loss of one billion dollars in Tasmania alone.
