Scientists recently filmed hadal snailfish living five miles below sea level. What would happen in one of them were brought to the surface? Would it pop? Could it survive? How do they manage not to get crushed at such depths?
They would explode, I imagine. The pressure inside the body of the fish counters the water pressure. Remove the water pressure and the fish pops. I don’t know if you can get them up to this level of relative vacuum.
There have been scholarly papers and research into ways to successfully bring deep-sea life to the surface for tissue research.
I’m not sure they would explode. A fish is an open system that exchanges fluids with the surrounding water, so I would expect the fish’s internal pressure to drop along with the surrounding water pressure. At some point the internal pressure change would kill the fish, but I am not exactly sure how.
Then again, I am thinking about gradually bringing the fish up to the surface. If the change were more sudden (for example if you sealed the fish in a pressurized container, pulled it up to just below the surface and opened it) perhaps the fish would explode.
Explode is probably overdramatic but their eyes would pop out, their swim bladders would swell out of their mouth, and the ascent would kill them.
I’ve seen marine biologists bring fish up from below 100m, they have to stop and decompress the fish’s swimbladder with a hypodermic needle at several points on the ascent.
Considerable volumes of gas emerge from relatively small fish.
In that case, I’d WAG that a very gradual ascent would minimize depressurization problems. I’m thinking the same way SCUBA divers decompress on the way back up by stopping several times in the ascent. The temperature change, however, would be another issue.
I have seen fish brought up from 100m or so, without time to decompress. Their eyes were indeed popped out… and they were swimming upside down in the tub.
I wonder if super-deep-dwelling fish could survive even if they were brought up very gradually, because chemical equilibria change at different pressures. The chemical reactions they depend on for life might not work at the right rates (or even in the right phases) at surface pressures.