Deepest Fish Caught on Camera (Pressure Can’t Crush It)

The deepest fish ever caught on camera is a snailfish, filmed 8,336 m (27,349 ft) down in the Izu-Ogasawara Trench south of Japan in August 2022. That’s almost as deep as Mount Everest is tall.

How does a soft little fish survive that much pressure? It brought no air. Lots of fish float on a gas-filled swim bladder; snailfish don’t have one. Their bodies are soft jelly, mostly water, and water barely squishes, so it pushes back just as hard as the ocean pushes in. Even their skulls aren’t fully closed.

But there is a limit. Pressure also bends the tiny protein machines inside a fish’s cells, and deep fish protect them with a molecule called TMAO (the stuff that turns into that fishy smell). The deeper a fish lives, the more TMAO it needs, and scientists think that around 8,200 to 8,400 m a fish can’t hold any more. No fish has ever been seen below about 8,400 m (27,560 ft). The trench keeps going for about another 2.5 km.

A plastic bag, though, has been found at 10,898 m in the Mariana Trench.

Season 2 of QuirkScience goes to the bottom of the ocean. Next: what lives at the bottom of the Mariana Trench, below the last fish.

Sources:
The deepest fish ever filmed (University of Western Australia, 2023):
What is the deepest living fish? (NOAA Ocean Exploration):
Mariana snailfish body and skull (Wang et al. 2019, Nature Ecology & Evolution):
TMAO and the depth limit for fish (Yancey et al. 2014, PNAS):
The plastic bag at 10,898 m (Chiba et al. 2018, Marine Policy)

#science #ocean #deepsea #snailfish #marianatrench #quirkscience

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