Deepest swimming fish confirmed in the world
Scientists from Japan and Australia have documented the deepest living fish to date, filmed 8 kilometers below the ocean surface. The creature, a snailfish of an unknown species, was observed at a depth of 8,336 meters in the Izu-Ogasawara Trench off southeast Japan. The expedition, which began last year, used divers and autonomous deep-sea equipment to capture the moment, marking a historic milestone in marine biology.
Shortly after the initial sighting, researchers confirmed the discovery of two additional snailfish, tentatively identified as Pseudoliparis belyaevi, in the same trench at depths around 8,022 meters. These findings argue that records at depths surpassing 8,000 meters are now part of the documented marine catalog, expanding our understanding of how life adapts to extreme pressure and darkness.
Participants in the Minderoo-UWA Deep Sea Research Center from Western Australia led the exploration of the Izu-Ogasawara and Ryukyu trenches in Japan. The campaign targeted depths of 8,000, 9,300, and 7,300 meters as part of a ten-year project to map the world’s deepest fish stocks. The team deployed autonomous submersibles and bait cameras to observe the organisms that inhabit these remote pits without disturbing them.
According to the expedition’s lead scientist and founder of the Minderoo-UWA center, evolutionary adaptations allow some snailfish to tolerate depths roughly 1,000 meters deeper than relatives living higher in the water column. This insight highlights how life can push the boundaries of what is biologically possible in oceanic trenches.
Across the deep seas, more than 400 snailfish species occupy a wide range of habitats. In the chokepoint of 8,000 meters and beyond, the pressure is immense—about 800 times greater than at the surface. Yet these animals persist, adapting in ways that scientists are still decoding, from their sensory systems to their metabolic strategies.
The discovery surprised many observers. Lead researcher Alan Jamieson notes that conventional expectations about the appearance of the deepest-dwelling fish often include features like knarled bodies, darkness-black coloration, long teeth, and tiny eyes. Yet the snailfish found at these depths show that appearance is closely tied to the darkness and the pitch-black environment rather than to depth alone. Deep-sea adaptations often manifest in subtle, surprising ways rather than through obvious signs of ruggedness or aggression.
Young fish reach greater depths
In the footage and samples examined, the deepest individual appeared to be a juvenile. Unlike many deep-sea species, young snailfish tend to occupy deeper zones than adults, a pattern that puzzles and fascinates researchers. The longevity of life at such crushing depths means many areas remain understudied, with ongoing questions about how early life stages survive predation and food scarcity in the abyss.
Researchers explain that the shallow portions of a deep-sea range often overlap with other deep-sea species, which may increase the likelihood that fry in the upper reaches fall prey to larger predators. The Japan expedition reinforced the theory that the Mariana snail, previously reported at 8,178 meters in the Mariana Trench, is not the deepest known fish after all. The records are now shifting toward even more extreme depths, driven by advances in submersible technology and deep-sea imaging.
In discussions about the limits of life, Jamieson recalls how, about a decade ago, his team suggested it might be biologically impossible for fish to survive beyond certain depths, roughly between 8,200 and 8,400 meters. The latest observations challenge that assumption, underscoring how little is understood about the physiology of these remarkable animals. Snailfish, usually associated with shallower habitats like estuaries and coastal zones, demonstrate a remarkable capacity to thrive far from those environments.
At these depths, individuals measuring roughly 20 to 25 centimeters feed on tiny crustaceans. These crustaceans in turn rely on the detritus and organic matter that slowly sinks toward the bottom from surface waters. The process can take weeks or months, and the abyssal scavengers are adapted to endure long intervals between meals. The deep-sea food web hinges on these fragile chains of survival, revealing how ecological relationships extend even into the most remote corners of our planet.
As the research continues, scientists anticipate more revelations about the organisms living in the world’s deepest trenches. The ongoing work aims to illuminate how generations of life cope with crushing pressures, near-freezing temperatures, and perpetual darkness, offering insights into the resilience of life in extreme environments. The Minderoo-UWA team stresses that each new discovery builds a broader picture of deep-sea biology and the evolutionary innovations that sustain life at the very edge of our oceans.
The momentum behind these expeditions reflects a growing scientific commitment to understanding the deep ocean. It also underscores the need for careful stewardship of marine ecosystems as researchers unveil more about the adaptations that enable life to persist under conditions once thought impossible.