Can fish survive in water irrespective of its salinity?

I suppose fish need a certain salinity level in water to survive - by that logic, a freshwater fish wouldn’t survive in seawater, right?

I guess they wouldn’t survive. I think my first fish pet died because I messed with its water conditions. RIP fishy

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Yes, I have heard a lot of such stories.

Marine and fresh water fishes are adapted to their respective environments by clever osmoregulations. Fresh water fishes retain the most salts and ions whereas the marine fishes pump out as much salts as they can to maintain their cells osmosis balance. However there are some exceptional fishes such as salmon that can survive in both the environments.

Check out this article


Hey! Thanks for posting that. I remember being so fascinated when we were publishing this article. It’s obvious that saltiness would affect fish, but we tend to look at all fish as this giant collective. What I found especially interesting about that article was that salmon can adapt to both freshwater and salty ocean water!

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Thanks for sharing this. Do you know if that can happen instantly? Like, if I pick a salmon from the sea and put it in a freshwater lake, will it adapt to the new environment?

Nope. Salmon are born and grow up in freshwater, and their bodies change to accommodate salt water as they age. Their body once more adapts to fresh water as they swim upstream into rivers where they reproduce. So, it does take some time for the salmon to get used to the different salt concentrations

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