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Killer Starfish Threaten Fish That Walks on Handlike Fins

A recent survey found just 79 spotted handfish in the waters off Tasmania

This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American


I know this is a column about endangered species, but I’m going to talk about comic books for a moment.

Bear with me.

Back in 1960, in the pages of The Brave and the Bold, No. 28 (the first appearance of the Justice League of America), writer Gardner Fox and artist Mike Sekowsky introduced one of the weirdest comic-book villains of all time. Starro (sometimes referred to as Starro the Conqueror) was a giant alien starfish that invaded Earth, spit off waves of mind-controlling clone offspring and tried to take over the planet. Only the combined might of Batman, Superman and a host of other heroes managed to defeat him.


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Starro may be fiction but invading starfishes are all too real. In Australia the invader is the northern Pacific sea star (Asterias amurensis), a species native to China and Japan that has traveled all over the world in larval form in the ballast tanks of big ships. Labeled as one of the world’s worst invasive species, these sea stars grow quickly in their new environments, reproduce quickly and are voracious predators that will eat just about anything they can find. The only thing that sets them apart from Starro is their lack of mind-control abilities.

Northern Pacific sea stars have caused massive damage in Australia, most notably around the island state of Tasmania. There they have put a unique native species—one that really does look a bit like an alien—on the fast track to extinction.

Until about 20 years ago, the spotted handfish (Brachionichthys hirsutus) was fairly common in southeast Tasmania. This cold-water species only grows to about 120 millimeters in length but it’s not its size that’s notable. Its fins are what stand out. The spotted handfish has enormous pectoral fins that (as you might guess from their name) look remarkably like human hands. The fish uses these fins to walk along the ocean floor. It is rarely seem swimming.

In fact, it is rarely seen at all these days. Invading sea stars have eaten so many handfish and their eggs that a recent survey of Tasmanian estuaries only came across 79 of the critically endangered fish.

The ocean is full of stars.

That doesn’t mean there are only 79 fish—the previous estimate was about 2,000—but it is worrisome news. In response an emergency workshop will be held next month to discuss launching a possible captive-breeding effort to save the species before any more of them disappear and create an insurance population, just in case they continue to vanish from the ocean.

Captive breeding “is tricky,” says Tim Lynch, senior research scientist with CSIRO, an Australian federal research agency. “The main issue is getting the young to take food,” he adds, and determining the right feed composition.

But at least there would be young. In the wild right now there aren’t even many eggs. “The northern Pacific sea star eats the handfish’s breeding habitat and probably their eggs and nearly everything else,” Lynch says. Handfish often lay their eggs on stalked, filter-feeding marine invertebrates called sea tulips (Pyura spinifera), which the sea stars also eat. No habitat means no eggs.

If technicians can get enough fish to breed in captivity, the species is likely to rebound, Lynch explains. The species have already survived two near-extinction events—the first several centuries ago then another in the 1980s—so they’re pretty hardy. They’re also protective parents. Handfish lay their eggs in little packets that the parents guard for weeks until the young go through metamorphosis and emerge as tiny fish.

Captive-bred fish could then serve as ambassadors for the species and their ecosystems. “Handfish are a strange filly, a mysterious beast,” Lynch says. “This thing’s turning into a mystical beast. It’s becoming so rare and so unseen that it’s almost become a dragon.” Being able to display handfish and share them with people in Tasmania and broader Australia, he says, would help to make them more “real” to people and therefore easier to conserve.

Invading aliens aren’t the only threats handfish face in Tasmania. They also face a loss of their natural sandy ecosystem from coastal development. And nutrient runoff from nearby communities and businesses has enabled increased algal growth, choking out handfish in some locations.

Despite the risks, Lynch remains optimistic. “I think that at this moment we have a good chance to conserve the species,” he says. “There are still some reasonable populations in the wild and a lot of good will between industry, government and research. The main issue, as with most endangered species, is habitat quality. If we can work on this, with the handfish as a focus, then we can improve the entire ecosystem.”

That’s won’t be easy but it’s something we don’t even need Superman to accomplish.

handfish

Photos by and courtesy of Tim Lynch, CSIRO.

John R. Platt is the editor of The Revelator. An award-winning environmental journalist, his work has appeared in Scientific American, Audubon, Motherboard, and numerous other magazines and publications. His "Extinction Countdown" column has run continuously since 2004 and has covered news and science related to more than 1,000 endangered species. John lives on the outskirts of Portland, Ore., where he finds himself surrounded by animals and cartoonists.

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