Fish from Salt to Fresh
Name: Chance M.
Is it possible to convert a Salt water Fish (for Example
a Moorish Idol) using a means of lessening the salt in the water each
time, into a fresh water fish?
You can't change an existing animal from one that does one thing into one that does another.
Evolution works on populations not on individuals. Some fish can tolerate moving from salt water
to fresh and back because it is already in their genetic program to do so (i.e., salmon) If you
took a large population of fish and changed the salt content slightly you may be able to select
for those that tolerate small differences in salt content. The ones that live will breed. If you
keep doing this over many generations, you may be able to artificially breed a species of fish that
has a tolerance for fresher water. You can't change a single fish into one that can tolerate a
decreasing range of salt in its life time. Each individual fish will either live or die.
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Update: June 2012