does the fresh water fish normally live in a hypertonic or a hypotonic" solution?

Question

what happen when you transfer it into salt water? pls answer with long

Answer 1

Fresh water is hypotonic with respect to the body fluid of the fish. Fresh water fish drink little water, but water gets into the fish by osmosis. The kidneys of frest water fish have to excrete large volume of urine.

When they are transferred to salt water, water gets out of their body by osmosis, since sea water is hypertonic. The fish have to drink a lot of water and they excrete a lot of urine, but they are not able to excrete the sodium. They die quickly.