Australia’s battle against invasive species is one of the biggest challenges facing our natural environment, and one that will undoubtedly persist for decades to come. Since European colonisation and the introduction of feral pests including cats, foxes and pigs, countless native species have become extinct, with many more classified as vulnerable.
One of these vulnerable creatures is the spotted handfish. Fewer than 2,000 individuals remain in the wild, and it lives only in Tasmanian waters, primarily in the Derwent estuary and nearby coastal bays. It’s currently under threat by the invasive Northern Pacific Seastar — an unassuming yet devastating invader locals are determined to fight.
While governments and marine biologists agree total extermination is near-impossible, dedicated conservationists are working tirelessly to minimise its impact on fragile ecosystems.
Keith Thomas-Wurth is one of them. In an interview with Yahoo News, the Tasmanian revealed that he, alongside a fleet of other volunteers, has so far cleared an astonishing 239,202 seastars from waters around the Derwent since February, 2021. Collectively, this haul, he estimates, weighs in excess of 11,230 kilograms. And on August 23, the team removed yet another impressive truckload of seastars.
The incredible truckload of invasive seastars volunteer divers removed from the Derwent River. Source: Johnny P. Keane/Facebook
Why is the Northern Pacific Seastar considered such a pest in Australian waters?
It’s an uphill battle made worse due to the fact that seastars are prolific procreators, with females capable of laying 20 million eggs in the breeding season between July and October. But, Keith is determined to save the spotted handfish, and said “everyone can do something” to prevent “one more species from extinction.”
While a permit is required in Tasmania to get involved in removal efforts, due to the presence of native seastars, people are still encouraged to participate in citizen science and targeted removal programs under guidance, helping protect spotted handfish while ensuring native species are not harmed.
“I have always had a love for the sea,” he said. “There are many threats to the sea and the oceans right now. One way I can help is to protect the spotted handfish, which is on the endangered species list.
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“We have a binary choice at present. Continue the effort to protect the spotted handfish, or do nothing and risk it going extinct.”
Keith explained that of the clean-ups he’s been a part of, efforts have predominantly been focused on the Sandy Bay area, consisting of Derwent Lane and Nutgrove Beach, with other events taking place at the Bellerive Yacht Club, Bellerive Beach, Primrose Sands, Shelly Beach Koonya, Blackmans Bay, and Kingston Beach.
“In all the world, the Spotted Handfish is only in the Derwent River; if it disappears from here, it is gone forever,” he said.
With no natural predators in Australia, the Northern Pacific Seastar thrives in plague proportions after arriving in the country as stowaways on ships in the 1980s. Recent estimates suggest there are as many as 30 million in Tasmanian waters, where the species significantly impacts local ecosystems by preying on native shellfish, including commercially important species such as scallops and oysters.
A permit is required to remove seastars from Tasmanian waterways, due to the fact they can be easily confused with native species. Source: Facebook/Keith Thomas-Wurth
Are we fighting an impossible battle?
The Invasive Species Council’s Dr Tiana Pirtle says “we don’t have the tools” on a broader scale to totally eradicate the pest, but we can protect native species in certain pockets.
“This is a big issue for invasive species management,” she had earlier told Yahoo. “When you have open contiguous landscapes — like the entire ocean — it is nearly impossible to eradicate some species, even terrestrial animals in Australia.
“We will probably never eradicate feral cats from mainland Australia.
“We just don’t have the tools. You can control populations at a local scale in these open landscapes, but you’re always going to keep getting more individuals coming in, and that’s the same with the seastars.”
Dr Pirtle argued that controlling at a local level “can definitely protect some environmental assets”. “But, as soon as you remove a bunch of individuals, it creates a vacuum, and now there’s more resources available, and it’s quite attractive for new individuals to come in,” she said.
“Unfortunately, I think we are fighting a losing battle sometimes in that regard. But that’s not to say local control programs can make a difference at a very local scale.”
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