Growing longer than a school bus, weighing up to 275 kilograms, and featuring eyes the size of a large pizza – the largest of any creature on Earth – the giant squid (Architeuthis dux) has fired the imaginations of deep-sea explorers for decades. 

Now, for the first time in more than a quarter of a century, one of the ocean’s most elusive inhabitants has made its presence known in Western Australian waters.

Scientists analysing environmental DNA – genetic material shed invisibly by animals into the surrounding sea – found traces of giant squid across six separate samples drawn from two deep submarine canyons off the Nyinggulu (Ningaloo) coast. It is the first record of the species in Western Australian waters using eDNA protocols, and the northernmost confirmed record of Architeuthis dux in the entire eastern Indian Ocean.

But evidence of this giant squid wasn’t all researchers found.

The study – led by Curtin University in Australia and now published in Environmental DNA – has revealed the extraordinary biodiversity concealed within the Cape Range and Cloates submarine canyons, a region of deep, largely uncharted habitats plunging to depths of more than 4,500 metres, located approximately 1,200 kilometres north of Perth. 

The expedition, conducted aboard the Schmidt Ocean Institute’s research vessel Falkor, collected more than 1,000 water samples across the water column.

In total, the survey detected 226 species across 11 major animal groups – among them rare deep-sea fish, cnidarians, echinoderms, marine mammals and cephalopods. Dozens had never previously been recorded in Western Australian waters at all, including the sleeper shark (Somniosus sp.), the faceless cusk eel (Typhlonus nasus) and the slender snaggletooth (Rhadinesthes decimus). Deep-diving cetaceans – among them the Pygmy sperm whale and Cuvier’s beaked whale – were also detected, alongside an undetermined number of species that may yet prove new to science entirely.

“Finding evidence of a giant squid really captures people’s imagination, but it’s just one part of a much bigger picture,” said lead author Dr Georgia Nester, who conducted the research as part of her PhD at Curtin University and is now based at the Minderoo OceanOmics Centre at the University of Western Australia. 

“We found a large number of species that don’t neatly match anything currently recorded, which doesn’t automatically mean they’re new to science, but it strongly suggests there is a vast amount of deep-sea biodiversity we’re only just beginning to uncover.”

Every animal that moves through the ocean leaves behind a trail of genetic material that disperses into the surrounding water. By collecting water samples and extracting that genetic signature, scientists can build a detailed picture of which species are present without ever needing to see or catch them. 

Dr Nester noted that a single sample can reveal hundreds of species at once, making eDNA a transformative tool for environments where conventional cameras and nets might fail to capture the full picture.

There are only two other records of the giant squid from Western Australian waters, and no confirmed sighting or specimen had emerged in more than 25 years before this survey.

“This is the first record of a giant squid detected off Western Australia’s coast using eDNA protocols and the northernmost record of A. dux in the eastern Indian Ocean,” said Dr Lisa Kirkendale, Head of Aquatic Zoology and Curator of Mollusks at the WA Museum.

The survey also revealed that biodiversity in these canyons is not uniformly distributed but that different depths host fundamentally different communities, while neighbouring canyons (those in close geographic proximity) can support distinctly different ecosystems. 

The vertical stratification of life across more than four kilometres of water column is itself a finding of considerable scientific significance.

“Deep-sea ecosystems are vast, remote and expensive to study, yet they face growing pressure from climate change, fishing and resource extraction,” said senior author Associate Professor Zoe Richards of Curtin’s School of Molecular and Life Sciences. 

“Environmental DNA gives us a scalable, non-invasive way to build baseline knowledge of what lives there, which is essential for informed management and conservation. You can’t protect what you don’t know exists. The sheer number of discoveries, including megafauna, makes it clear that we still have so much to learn about what marine life lives in the Indian Ocean.”

With a clearer picture of deep-sea biodiversity, conservationists can guide marine park planning, inform environmental impact assessments, and establish the baselines needed to detect change over time. Until now, baselines such as these had not existed for canyons that had been previously unexplored.

“These canyons are incredibly rich ecosystems and, until now, they’ve been largely unexplored because of the difficulty of working at such extreme depths,” said Dr Nester. 

“With eDNA, a single water sample can tell us about hundreds of species at once. That means we can dramatically expand our understanding of deep-water environments in a way that simply hasn’t been possible before.”

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