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More people have seen a giant squid dead than alive. So little is known about these vast cephalopods that most of the information we have cobbled together has been shaped by a handful of corpses found splayed half rotten on beaches and rocks, or by the tall tales sailors have told of the times they grappled with the fearsome kraken—a monster that rivaled in size the ships they sailed. Modern biology and staggeringly difficult deep sea explorations have helped fill in some of the gaps in our understanding, but even so, giant squid remain frustratingly mysterious. To date, they have only been captured on film a handful of times, leaving scientists with lingering questions about their distribution and behavior.
Toshifumi Wada knew all of this as he dropped yet another bottle over the side of the fisheries research vessel Tajima one February morning in 2018. A marine biologist at the University of Hyogo in Japan and an expert in giant squid, Wada had made international headlines three years before as the first researcher to successfully identify juvenile members of the species. Now, as the Tajima bobbed in the Sea of Japan, Wada wanted to do one better: prove that he could find live giant squid without relying on catching them as by-catch, mapping strandings, or clambering into a deep-sea submersible. Instead, he would analyze the water collected in his specialized bottles for the trail of genetic debris left in the wake of these elusive cephalopods.
Every living organism sheds infinitesimal fragments of genetic material as scales, skin, gametes, fronds, or feces. Collectively, this precious detritus is known as environmental DNA (eDNA). By comparing this organic matter against a library of genome sequences, scientists can identify specific life forms. The technique would be perfect, Wada reasoned, for detecting the presence of a cephalopod only caught on camera four times.
While there was already evidence in by-catch, and in numerous stranding incidents, to suggest that giant squid were living in the Sea of Japan, both Wada and his collaborator, Hideyuki Doi, had their doubts that they’d actually be able to pick up their genetic trail. Doi, Wada’s colleague at the University of Hyogo and an expert in freshwater applications for eDNA, explains: “We imagined it was difficult to detect giant squid eDNA in such a big marine habitat.”
But after sampling water in the Sea of Japan at five sites, both at the surface and at a depth of 100 meters, in February, May, and August 2018, the pair were astonished: they had uncovered the genetic trail of Architeuthis dux—as the giant squid is formally known—but they’d also learned something new about how the squid lives. Giant squid DNA, the scientists later wrote, was “detected in winter but not in summer”—confirming the seasonality of the cephalopods in the Sea of Japan, and lending credence to a previously hypothetical migratory pattern.
The paper chronicling the discovery was to be Wada’s last. The professor died at age 40, in November 2018—mere months after collecting the last samples and confirming that they contained the genetic signatures of giant squid.
The legacy of Wada’s impulse to dive as deep as he could into knowing the giant squid, Doi believes, could lead to a fundamental breakthrough in our understanding of the cephalopod. Although the study is only a first step in the wider use of eDNA in the investigation of the giant squid’s distribution, further sampling could help solve mysteries about the animal’s chosen habitats. Additionally, says Doi, by identifying the best times and places to look, “eDNA tracking may increase the opportunity to observe the wild swimming giant squid.”
Edith Widder, a marine biologist at the US National Oceanic and Atmospheric Administration Office of Ocean Exploration and Research, is one of a handful of scientists who have successfully filmed giant squid in the wild. Using eDNA to detect the presence of giant squid at shallow depths as Wada and Doi did is relatively straightforward, she says. But doing it at scale, and at depths of 300 meters or more where adult giant squid are presumed to live, is a more time-consuming and expensive undertaking. In fact, Widder suspects the Japanese researchers’ discovery was evidence of juvenile giant squid, which live at shallower depths.
“You would need a lot of ship time to do the kind of seasonal geographic surveys required to pinpoint optimal hunting zones,” Widder says.
Widder isn’t certain eDNA would have been a useful tool in her own quest to film giant squid. The choice of her first staging area, off the Japanese coast in 2012, was partially informed by cases of sperm whales feeding on the cephalopods in nearby waters. “The location was important, but even more important was being unobtrusive,” says Widder—which meant dispensing with submersibles and their noisy engines, which she suspected scared away most giant squid. To be as stealthy as possible, Widder used an optical lure mounted on a camera platform to obtain her footage. Last year, she managed to repeat the same feat in the Gulf of Mexico—a shocking discovery, given there was no previous evidence for giant squid in the region.
Widder thinks this unexpectedly broad geographic distribution—and the many hundreds of giant squid beaks found inside the stomachs of sperm whales around the world—is evidence that the giant squid is much more common than previously believed.
“Our standard methods of exploration, with bright white lights and noisy thrusters, have been scaring them away,” she says. With more eDNA sampling expeditions to further refine our understanding of the giant squid’s preferred habitats, scientists could concentrate their efforts at specific sites and confirm, once and for all, whether its elusiveness is a symptom of its distribution or simply because it is shy.