A fish that walks on the seafloor has gone extinct. Can its cousins be saved?

For the first time in modern history, a marine fish species has been declared extinct. The smooth handfish (Sympterichthys unipennis), a shallow-water bottom-dweller with spiky fins and a barb-like protrusion on its forehead, has not been seen since 1802, when French biologist François Péron helped scoop one up near the coast of Tasmania to bring back to Paris’s Natural History Museum.

Despite extensive searches over many years, no smooth handfish were ever seen again. In May, the International Union for the Conservation of Nature (IUCN), a global consortium of scientists that sets the conservation statuses of species, formally listed it as extinct.

Thirteen other species of handfish—so named because they perch on the seafloor on fins that look like little hands and act like feet—are probably still around, though seven of the species haven’t been seen since 2000 or earlier. All but one species is considered endangered, critically endangered, or “data deficient,” meaning there’s not enough information available to decide their status.

The disappearance of the smooth handfish highlights how sensitive this family of fishes are to environmental disruptions such as climate change, habitat destruction, and pollution, because the smooth handfish was almost certainly common when scientists documented it for the first—and last—time, more than 200 years ago. Scientists say this milestone serves as a warning for what may come for other handfish species and other vulnerable, localized species in places like Tasmania.

“They’re a canary in the coal mine,” says Neville Barrett, an ichthyologist at Tasmania’s Institute for Marine and Antarctic Studies.

Brightly colored homebodies

“If you’ve never seen a handfish before, imagine dipping a toad in some brightly colored paint, telling it a sad story, and forcing it to wear gloves two sizes too big,” reads the description of the fish by the Handfish Conversation Project, led by a group of researchers from the Australian government and academic institutions devoted to the animals' conservation.

The author of the above description remains unknown, but it stuck, says Jemina Stuart-Smith, a marine ecologist at the Institute for Marine and Antarctic Studies at the University of Tasmania, and the Commonwealth Scientific and Industrial Research Organization.

Typically no longer than six inches, most handfish are believed to live only in the ocean around Tasmania. Even within those waters, each species is found at only a small number of sites.

They’re also homebodies. Handfish typically don’t disperse over long distances, and their young don’t go through a mobile, wide-ranging phase like many other types of fish. “They’ve got a strategy that works brilliantly in a stable environment,” Barrett says.

‘Perfect storm’ of threats

It’s not known exactly what combination of factors led to the smooth handfish’s extinction, but handfishes’ homebody ways, limited geographical ranges, and preference for cold water make them especially vulnerable to environmental disruption.

Near Hobart, Tasmania, for example, runoff and heavy metal pollution from various industries have degraded the water quality in estuaries along the coast, the predominant habitat of the spotted handfish and other handfish species, says Graham Edgar, a marine biologist also at the Institute for Marine and Antarctic Studies. This worries researchers because, Edgar says, “if they’re lost from an area, they’re probably not going to come back.”

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Historic dredging for scallops, destruction of oyster reefs, and introduction of non-native species in Tasmania’s waters likely have also had significant effects on handfish numbers.

Probably the biggest threat, however, is warming waters. Handfish once roamed over a much larger area when the climate was cooler, Barrett says. Now, warming has forced many species, including handfish, some crustaceans, seaweeds, and many other cold-loving marine organisms into shrinking ranges. Tasmania is a hotspot for the handfish because its waters, though warming, are colder than those farther north.

This is changing, however, as the East Australian Current, which sweeps water down the coast from Brisbane to Sydney, has been pushing warmer water farther and farther south, Barrett says. Ocean temperatures in Tasmania have climbed by nearly 3.6 degrees Fahrenheit (two degrees Celsius) since 1900, according to the Met Office Hadley Center for Climate Science and Services.

“It’s been a perfect storm of different threats,” Edgar says, and it’s led not just to the extinction of the smooth handfish but to a “catastrophic loss of biodiversity” around Tasmania, with big declines in the populations and ranges of various fish, bivalves, crustaceans, seaweeds, and other marine organisms.

Such declines may go unnoticed until it’s too late, because their habitats are underwater and out-of-sight, and because there’s a lack of data about their populations, Edgar says—as in the case of the smooth handfish.

Data deficiencies

There are concerted conservation plans for only three species: critically endangered red handfish, spotted handfish, and Ziebell’s handfish. Red handfish currently receive particular attention because there are only two known populations, both near Hobart, and there are thought to be fewer than a hundred adults left, Stuart-Smith says. (Read about the discovery of a rare red handfish colony in 2018.)

The plans for these species emphasize more data collection, prevention of habitat destruction, and, in some cases, introducing artificial substrates for the fish to lay their eggs on, to replace lost kelp and sea squirts (tube-like filter feeders), which have been destroyed by invasive sea stars and sea urchins.

“For the rest of the species, we’re lacking the information and resources needed to be able to implement conservation strategies,” Stuart-Smith says.

Because many handfish species are rare and hard to find, they’re difficult to study. Nonetheless, researchers continue to look for them, using new methods such as searching for fragments of their DNA in the ocean. Research on captive breeding also continues, Barrett says, though nobody has been successful at getting them to complete a full life cycle in captivity.

“Despite being such charismatic and quirky little fish... there is so little we know about them,” Stuart-Smith says.