Why can't marine fish live in fresh water?
Phil Henderson
(JackStraw9) wrote:
> While dining at a resturant in Florida recently, a waiter asked me why
> salt water fish can't live in fresh water (I was asking him about their
> marine tank, and told him I keep marine fish). I did not have a good
> answer for him- does anyone out there have an answer? Can any marine fish
> be adapted to fresh water, as some fresh water fish can be adapted to
> brackish water?
> Jay
Its an osmosis problem. Marine fish tissues are not as salty as salt water
so water wants to move from the high water concentration inside their
bodies to the lower water conc. outside their bodies. Their life is a
constant struggle to keep from becoming dehydrated and they have mechanisms
to prevent this.
Fresh water fish have just the opposite problem. Their tissues are saltier
than their environment and so the water wants to go into their bodies.
Freshwater fish are in constant danger of having their cells exploding from
too much water and they have mechanisms to prevent this.
Its not to hard to see that the two life styles are not interchangable. The
amazing thing is that there are fish that can go back and forth without any
major damage to their systems.
--
Phil Henderson
Brea, Ca
phen...@kn.pacbell.com
ao...@asuvm.inre.asu.edu
>From: pbo...@violin.aix.calpoly.edu (Paul Rene Borloz)
>Subject: Re: Why can't marine fish live in fresh water?
>Date: Wed, 15 Feb 1995 21:28:00 GMT
>: answer for him- does anyone out there have an answer? Can any marine fish
>: be adapted to fresh water, as some fresh water fish can be adapted to
>: brackish water?
>: Jay
>I don't know if it can be done, but I know a guy who is giving it a try.
>He took mollies to salt, and is now try to bring the mollies and a
>handfull of damsels back to fresh water (or brackish). For the fishes
>sake I hope it will work. When I find out what happens I will post.
>--
>Paul (pbo...@oboe.aix.calpoly.edu)
You should tell your friend to stop the experiment with damsels immediately
because it will not work. Fresh and salt water fish have very different
physiologies. Fresh water fish must have kidneys capable of producing copious
amounts of very dilute urine. Salt water fish need the opposite - kidneys
that can produce very concentrated urine. Salt water fish also need chloride
cells in their gills to help them get rid of excess salt they take it when
they drink. Some fish, like mollies, have both sets of physiologies and can
make the adjustment if it is done gradually. Most fish, damsels included,
have only one kidney/gill configuration and will only die if you move them, no
matter how gradually, to the wrong osmotic environment. Mike Moore
Dreamer
The body chemistry of a fish is adapted it's enviroment. if you put the
fish in water with too much or too little salt the chemistry is
disrupted. depending on the salinity, either the H2O in it's cells
will decrease, killing it by dehydration, or increase, drowning it.
there are some fish that can adapt to one or the other, Scats for one.
--
Forget the adresses, just send me the phone numbers of single women
between 21 and 35. Or money, cash is always accepted with gratitude.
-Dave Haun 1 Feb 95
Michael Moore
>
>The body chemistry of a fish is adapted it's enviroment. if you put the
>fish in water with too much or too little salt the chemistry is
>disrupted. depending on the salinity, either the H2O in it's cells
>will decrease, killing it by dehydration, or increase, drowning it.
>there are some fish that can adapt to one or the other, Scats for one.
>
can be done. A salt water fish can be adapated to live in a fresh water
environment. I've never done it myself, but I have seen it done. I have
known of puffers (one of the stores around here sells them) that have
been adpated to live in freshwater environment.
Mikew :)
--
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<->>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
> You can lead a horse to water, but you can't make him drink. >
< You can put a fish in water, but you can't make him swim. >
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<->>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Jeffery Schafer
>In article <3i509g$h...@terrazzo.lm.com>, dre...@telerama.lm.com says...
>>
>>The body chemistry of a fish is adapted it's enviroment. if you put the
>>fish in water with too much or too little salt the chemistry is
>>disrupted. depending on the salinity, either the H2O in it's cells
>>will decrease, killing it by dehydration, or increase, drowning it.
>>there are some fish that can adapt to one or the other, Scats for one.
>>
>(some)Fish are adaptable. It is a long and painstaking process, but it
>can be done. A salt water fish can be adapated to live in a fresh water
>environment. I've never done it myself, but I have seen it done. I have
>known of puffers (one of the stores around here sells them) that have
>been adpated to live in freshwater environment.
Could someone tell me which fish can be converted. Can porcupine puffers?
Also, what is the process?
Thanx,
Jeff
Valerie Haecky
I used to keep puffers in freshwater, and they did reasonably well.
On thing I was told was that they need to be converted when they
are small, that is about an inch or so, and that it cannot be
done with adult fish. Just what I heard. I bought the fish after
they were converted.
Valerie
--
__
_______ /*_>-< Valerie Haecky _ ^---^
___/ _____ \__/ / v...@intellicorp.com <_|-----)>
<____/ \____/ (415) 965-5617 x617 v---v
Richard G. Wehby
some exceptions, i.e.: hagfish) are hypo-osmotic. All freshwater fishes are
hyper-osmotic. For a complete discussion see an animal physiology textbook
(e.g.: Schmidt-Knielsen, 1991, _Animal_Physiology:_Adaptation_and
_Environment_).
Richard