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17 October 2015

Japanese Starfish (Asterias amurensis)

Japanese starfish (Asterias amurensis)

Whilst I was on holiday in Australia earlier this year, I was chatting to a fisherman who was fishing from the jetty in Port Philip Bay.  He reeled in one of his rods and discovered that he had hooked a bright yellow starfish.  Seeing that I was curious he told me it was a Japanese starfish otherwise known in Latin as Asterias amurensis. The fisherman said although it was a species originally native to Japan, China and Korea it had recently been introduced to Australian coastal waters along oceanic shipping routes.  Following my informative chat with the fisherman, I carried out further research on the internet and I learnt that the larvae of the Japanese starfish was apparently transported in the ballast water of ships.  It had invaded Australian waters and had bred prolifically due to the fact that it has no natural predators in Australia.  It has been classified as an invasive species in Australia and is on the Invasive Species Specialist Group list of the world's 100 worst invasive species

It struck me that whilst the scenery around Port Phillip Bay is certainly idyllic, there is so much going on under the water such as the reproduction of the invasive Japanese starfish.  I'm sure the Australian Fisheries Management Authority and marine biologists are fully cognisant of this problem however, by doing a blog post I wanted to raise awareness.  The fisherman I spoke to said, that if they happen to catch a starfish on their rods, they had been advised to destroy it and dispose of it in the bin and not throw it back into the water.  

I am including an extract below from the Wikipedia website on the "impacts on society" and a bid to try and effectively remove the Japanese starfish from Australian waters without causing too much environmental damage. 

Impacts on society

Invasions breed extinctions. It is vital to monitor ecological impacts from invasive species, because they can cause economic or even human health impacts. A surge in this species’ population will affect the populations of its prey and throw off normal balances in the current trophic web of Pacific coast areas. Experimental evidence has concluded that the predatory star has a major impact on juvenile bivalves. The asteroid will also attach itself to salmon traps, oyster lines and scallop long lines. In Australia, it was connected to the decline of the endangered hand-fish. American ecologists must pay close attention to the implications of this invasive species. As trophic webs change over time, the endangerment and loss of certain marketable sea organisms cause coastal communities to potentially lose billions of dollars. In Japan, the sea star’s population outbreaks have cost the marine culture industry millions of dollars in control measures and losses from predation.

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Removal

The North Pacific sea star has already invaded Australian waters in the Derwent Estuary and Henderson Lagoon. Such a notable disturbance has not been documented in America.

Trials have been run to find effective removal processes including physical removal of A. amurensis, which was estimated by workshop participants to be the most effective, safe and politically attractive when compared with chemical or biological control processes.  Poisoning the sea-stars or introducing a new predator to cut back their population numbers would introduce new problems, so effectiveness is not guaranteed. Early detection and prevention of reproduction remains the best solution to reducing harmful effects of invasive species. The aim of the study by Mountfort et al. was to develop a probe to test ballast water and detect the presence of this specific maritime pest.  If policies on removal of ballast water are enforced, the star fish will not be introduced to foreign systems so frequently.
 https://en.wikipedia.org/wiki/Asterias_amurensis
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