What is the deepest-living fish?
The deepest confirmed fish sighting is of a snailfish filmed at a depth of 8,336 meters (27,000 feet) below the ocean surface. Other fish may live at similar depths, but it’s likely that no fish lives deeper than about 8,400 meters (28,000 feet) because of the deep ocean’s extreme pressure.
An example of a deep-sea snailfish. The fish in this video was spotted at a depth of 1,365 meters (4,480 feet) during dive 8 of NOAA Ocean Exploration’s 2023 Seascape Alaska 5 expedition. The deepest-living snailfish ever seen was found by Jamieson et al. in 2023 at more than 6 times this depth! Download HD version (mp4, 19.6 MB)
Snailfishes are a group of tadpole-like fish with large heads, small eyes, and no scales. They’re found all around the world from shallow, coastal seas to ocean trenches. Some snailfish species are especially well adapted to deep water: The deepest snailfish ever filmed was recorded at 8,336 meters (27,000 feet) below the ocean surface. That’s deeper than all but the highest mountains are tall, and it’s about 1,000 meters (3,300 feet) deeper than any other type of fish has been seen alive.
The snailfish’s record is certainly impressive, but it still doesn’t come close to the deepest point in the ocean: The Challenger Deep in the Mariana Trench is about 11,000 meters (36,000 feet) below the ocean surface. So will anyone eventually find a fish living even deeper than the snailfish? It’s possible. In 1970, a deep-sea cusk eel was caught in a net that descended to 8,370 meters (27,460 feet), though it’s hard to know for sure whether the cusk eel was caught at the trawl’s deepest point.
While cusk eels and other rivals might compete for the title of deepest-living fish in the future, there’s good reason to believe that deep-sea snailfish live about as deep in the ocean as any fish can. Research suggests that there may be a boundary between 8,200 and 8,400 meters deep (27,000 to 28,000 feet) beneath which no fish can live due to the crushing pressure of the deep ocean. Deep-sea snailfish are able to survive extremely high water pressure, but even their bodies have limits. Below this boundary, all animals discovered so far have been invertebrates without bony skeletons like sea cucumbers and isopods.