Researchers using an ROV recorded rare footage of a faceless cusk eel off the Cook Islands — a species first described in 1878 and rediscovered in 2017. Adults lack visible eyes and have a mouth on the underside of the body; they inhabit cold, dark waters down to roughly five kilometres (3.1 miles). Little is known about their population or life cycle. The sighting highlights the value of remote cameras and submersibles for studying deep-sea biodiversity as interest in deep-sea mining grows.
Rare 'Faceless' Cusk Eel Filmed by ROV off the Cook Islands — A Glimpse into the Deep
Researchers using an ROV recorded rare footage of a faceless cusk eel off the Cook Islands — a species first described in 1878 and rediscovered in 2017. Adults lack visible eyes and have a mouth on the underside of the body; they inhabit cold, dark waters down to roughly five kilometres (3.1 miles). Little is known about their population or life cycle. The sighting highlights the value of remote cameras and submersibles for studying deep-sea biodiversity as interest in deep-sea mining grows.
11:44 AM, 11/18/2025Science
Deep-sea cameras capture exceptionally rare 'faceless' cusk eel
Researchers studying life in the deep Pacific recorded footage of an exceptionally rare fish — the so-called faceless cusk eel — using a remotely operated vehicle (ROV) off the Cook Islands.
The species was first described by an expedition in 1878 and went unseen until it was rediscovered in 2017. True to its name, adult faceless cusk eels appear to lack a conventional face: juveniles may have eyes hidden beneath the skin, but adults show no visible eyes and have a mouth positioned on the underside of the body, giving them an eerie, featureless appearance.
These unusual fish live in some of Earth’s most hostile environments — cold, dark waters thousands of metres below the surface. They are adapted to depths of up to about five kilometres (3.1 miles). With sunlight absent at those depths, they rely more on chemical cues and smell than on sight to find food, feeding mainly on bottom-dwelling crustaceans and other invertebrates.
Because sightings are so rare, scientists know very little about the faceless cusk eel's population size, reproductive biology, or lifespan. Discoveries like this underscore how much remains unknown about deep-sea ecosystems.
Why this sighting matters
The deep ocean is still largely uncharted: the National Oceanic and Atmospheric Administration (NOAA) estimates that nearly three-quarters of the seafloor have not yet been mapped, and a May 2025 study estimated that roughly 66% of Earth's surface area qualifies as deep sea. Remote cameras and unmanned submersibles are therefore essential tools for documenting biodiversity in these remote habitats.
Footage from ROVs can reveal previously unseen life and inform conservation decisions at a time when interest in deep-sea exploration and potential mining is increasing. Better scientific knowledge helps policymakers and international organizations weigh the ecological risks of new activities on the ocean floor.
"Capturing these creepy critters on camera hasn't been easy," the Ocean Exploration Trust said. "The deep-diving capability of ROV Little Hercules allows us to meet these representatives of the Cook Islands' biodiversity for the first time."
As this sighting demonstrates, much about the submarine world remains to be discovered — and each observation helps paint a clearer picture of life in the deep ocean.