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Name: Steven W.
Status: student
Age: 10
Location: N/A
Country: N/A
Date: 2000-2001

I would like to know if there are any fish that can live in both salt and fresh water. I believe the guppy might. If so what would the difference in their genetics (or gills) have to be for them to be able to do this?

Fish that can live in both salt and fresh water are called osmoregulators. Salmon is an example. They hatch in fresh water, swim to the ocean and spend most of their lives there. They then swim back to their spawning grounds (where they hatched) to lay their own eggs. They go from fresh to salt water and back again. They regulate their salt intake through their kidneys and their gills. Excess water can be lost through the gills and excess salt can be lost through the kidneys.


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