3 days ago
Divers haul 160kgs out of Aussie river as invasive critter threatens rare species
Seven divers and five snorkelers donned their wetsuits and plunged into a frigid Australian river over the weekend in a desperate bid to drag a troubling invasive species out of the water and protect vulnerable sea life.
In just one hour, the swimmers removed 160 kilograms worth of Northern Pacific seastar from the River Derwent in Tasmania. The marine creatures are notorious for their impact on the native spotted handfish — a species barely hanging onto existence due to the predatory seastars.
Keith Thomas-Wurth volunteers with Invasive Seastar Clean Up, and told Yahoo News more than 3,500 seastars were removed by hand during the effort. Every single removal is crucial, he said.
"The divers go down, pick them up with their hands, put them in catch bags, and then they're brought to shore," he told Yahoo, explaining the seastar breeding season is just beginning.
"The female seastar will lay up to 20 million eggs in the six to eight weeks of the breeding season... The seastars destroy the spotted handfish habitat, destroying the growth that comes out of the sea floor where they lay their eggs, so they have nowhere to put them."
The seastars pose a significant conservation threat to the spotted handfish because they not only prey on the sea squirts where the fish lay their eggs, but they also prey on their eggs.
"The seastars create problems for the little spotted handfish which are only found in the river, they're nowhere else in the world," he said. "[The seastars] aren't freshwater-tolerant so we put them in some, and it kills them immediately."
There is estimated to be less than 2,000 spotted handfish left in the wild, according to CSIRO.
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Organisation has removed 11 tonnes of seastars in four years
Since the Invasive Seastar Clean Up started in February 2021, more than 11 tonnes of seastars have been removed by volunteers in the four years it's been running. Keith explained the team keep note of every clean-up effort and has counted more than 235,000 seastars removed from the River Derwent.
Not only do the Northern Pacific seastars impact spotted handfish, but they also have been harmful to native seastar species such as the Tasmanian live-bearing seastar and the Bruny Island seastar. The invasive species outcompete local populations for food and space, and have rapidly disrupted the balance of marine ecosystems.
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