Salt and Fresh Water Fish
Name: Steven W.
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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Update: June 2012