Two teams of scientists from Japan and Australia have pushed the limits of known marine life by recording the deepest swimming fish on Earth. A snailfish was captured moving at a depth of 8,336 meters in the Izu-Ogasawara Trench off southeast Japan, setting a new world record. The footage came from a diver who joined an expedition that began the previous year and explored the trench system for clues about life in extreme darkness and pressure.
Shortly after that discovery, researchers located two more snailfish—Pseudoliparis belyaevi—in the same trench at roughly 8,022 meters. Officials said these sightings mark the first confirmed recordings of fish below 8,000 meters, underscoring how much remains unknown about life in the deepest parts of the ocean.
Investigators from Minderoo-UWA Deep Sea Research Center in Western Australia and the Deep Sea Research Center at Tokyo University of Marine Science and Technology coordinated the effort, which surveyed the Izu-Ogasawara and Ryukyu trenches in depths around 8,000, 9,300 and 7,300 meters as part of a decade-long study on the planet’s deepest fish stocks. Autonomous deep-sea submarines and bait cameras were deployed to observe those remote pits, with teams planning ongoing observations in the coming years.
Lead scientist Professor Alan Jamieson, founder of the Minderoo-UWA Deep Sea Research Center, noted adaptive strategies that allow certain snailfish to endure about 1,000 meters deeper than related species found higher up in the water column. The deep-sea environment drives surprising changes in anatomy and behavior, often making such creatures appear less typical than one might expect from surface-dwelling fish.
More than 400 snailfish species are known to inhabit a wide range of habitats, from sunlit shallows to the perpetual darkness of deep oceans. At depths surpassing 8,000 meters, pressure is roughly 800 times greater than at the surface, shaping physiology in dramatic, unseen ways.
Observers were struck by the appearance of the deepest fish. Jamieson remarked that popular ideas of what the deepest creatures look like often include gnarly bodies, dark coloring, and enormous teeth with tiny eyes. He suggested that such traits are less about depth itself and more about the darkness and remoteness of those zones. Deep-sea adaptations tend to be subtle and less conspicuous than surface-dwellers would expect.
Juveniles go deeper
The recording highlighted a juvenile snailfish as the deepest individual, a notable detail since young snailfish often inhabit zones deeper than adults. This arrangement creates a narrow window for survival, where fry in deeper ranges face intense predation from nearby deep-sea species more than anything else in their environment, according to Jamieson.
The Japan expedition reinforced a theory about the Mariana snailfish, which was found at about 8,178 meters in the Mariana Trench in 2017, indicating that it may not be the deepest fish known to science.
Historical estimates from about a decade ago suggested it might be biologically impossible for fish to survive beyond roughly 8,200 to 8,400 meters. The new findings show that certain snailfish can tolerate depths beyond that previously assumed limit, revealing the remarkable capacity of life to adapt under extreme pressure.
It remains intriguing that snailfish, not typically deep-sea specialists, have adapted to depths greater than many vertebrates can endure. Most snailfish typically thrive in shallower waters such as estuaries, but some lineages appear to push the frontier of depth. At those extreme depths, fish measuring roughly 20 to 25 centimeters feed on tiny crustaceans, which in turn subsist on organic material falling from above. The sinking of material can take weeks or months to reach these depths, creating a unique food chain. The deep-sea crustaceans, hungry as ever, seize these opportunities even when decay signals are slow to arrive.
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