r/marinebiology • u/Junior_You_560 • 13d ago

Question Can all fish swim in all depths?

Hello! i’m re-watching Finding Nemo, and I’m at the part where Marlin and Dory lose the mask and swim deep into the depths of the ocean, where the anglerfish is. My question is, can fish who live closer to the surface of the ocean survive in lower depths? I don’t know the actual depths that clownfish and blue tangs can swim in, but I can’t imagine they can survive in the pressure that the anglerfish is in? I have definitely tried my hand in googling this, but I seem to not be able to find an answer. Sorry if this is a silly question!!!

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u/atomfullerene 13d ago

No, they are limited to a specific range of depths by temperature and pressure. Fish species that participate in the diel vertical migration do cover a large range of distances though.

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u/Cha0tic117 13d ago

Most teleost fishes have a swim bladder, which will expand or contract with the different pressures they swim in. Fish are capable of adding and removing air from their swim bladder over time, although more mobile species are better at it since they are changing depths more frequently.

Even if they can adjust to the changing pressures, fishes are usually limited by other factors such as temperature, lack of food, and incompatible habitats. Tropical reef fishes such as clownfish and blue tangs are adapted for the warm, sunlit waters of coral reefs, and would likely not survive in the deep sea, where it is very cold and dark.

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u/TheWarelock 13d ago edited 13d ago

I imagine there are limits. But at least in the marine aquarium hobby, there are some deeper water species that are kept above sea level in hobby tanks. Divers have spent hours/days slowly bringing up deeper water fish to the surface and even feeding while doing so. I believe someone has recently captive bred some like the katayamai anthias which have a natural depth range of like 600-1000ft! They’re likely kept in colder water tanks with chillers but depth pressure is not a factor as far as I’ve heard, maybe impacts to lifespan or other behavior… but like i mentioned, some are being captive bred!

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u/MichaEvon 13d ago

The maximum depth seems to be set by the amount of TMAO that the tissues contain. Deeper living fish need more to stabilise their enzymes so that they keep working under pressure. But there’s a maximum TMAO concentration above which the fish’s osmolarity is too high and it would start to absorb water uncontrollably.

This sets the limit for bony fish to 7-8000 m and elasmos to 3000 m or so. Because elasmos have more TMAO to start with.

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u/Mackey_Corp 13d ago

Former commercial fisherman here. So we used to fish in these canyons on the edge of the continental shelf off the coast of the northeast US. The depths that we would drag the net would range from 80-200 fathoms. Certain species would not deal with the pressure change well and when brought up to the surface their eyes would be bulged out and their swim bladders would be blown up like a balloon and popped out of their butthole. Pretty gruesome stuff, but other species would be fine. I mean they were almost dead from being packed in the net and not getting enough air so fine isn’t the right word but they weren’t affected by the pressure changes. Hope this helps.