RE: [GSAS-Member] Fish & temperature?

["Hess, Clay A" <clay.a.hess@boeing.com>]

Hmmmmmm, again, this is an interesting issue too.  My experience with
fish and temperature changes has been both good and bad.  First, I
should note that I change my water directly from the tap and check the
temperature coming from the tap by fingertip (yeah, Mr Engineer uses his
fingers, good to plus or minus ~3 degrees).  Second I should mention I
check my temperature to the Celsius scale (only because that is the type
of thermometers I have).  Third I will mention that I have fish from
Asia, Africa and South America mixed in most of my tanks (Ack!! How can
that be??)

Soooo, ok, stick to the question please.  Fish and Temperature.  Oh
yeah.  Let's look at an example a little closer to home to see if we can
draw some possible parallels to the aquatic world.  How about people?
You, me, the kid next door....perhaps the kid next door is the best
example, or, even my own kids.  Kids do not wear coats.....simple fact.
I don't care what the temperature is outside, they do not wear
coats....unless forced to do so.  Do kids get sick every time they go
out the door?  Nope.  Can they go out in hot weather without a coat and
suffer no ill effects?  Sure.  How about warm weather?  Absolutely.  Ok,
let's get to the cold weather level?  Sure, they can play in cold
weather without a coat and do fine too.  Freezing weather?  Yep, this
works too.  Seen it with my own eyes.  Annnnnnnnnnd, I am sure if most
of us think back to our childhoods (which for me is a bit of a
challenge) we will remember times when we played outside in the cold
without coats too and suffered no ill effects.  The key is the amount of
exposure to the outside temperature and health of the individual when
temperature change occurs from what I have seen.

For instance......kids playing outside in 40 F degree weather, without a
coat, can go for hours with no significant impact, except rosy cheeks
perhaps.  Go to temperatures below freezing and now it is a matter of
how long the extremities (fingers, toes and nose) can handle the cold
before the initial effects (burning sensation) of frostbite set in.
Yet, even when we begin to feel the first stages of frostbite it does
not mean that one will become sick from it.  It's amazing how well a
person can adapt to temperature changes from about 25 F to 100+ F with
no ill effects.  

Now, let's expose that same person to a cold or flu virus or bacteria
and do the same thing.  Seems that the person is more apt to becoming
ill as a result. The temperature change is an added stress (your body
will try to maintain its set temperature) on the body's system that
makes it easier for the virus or bacteria to overwhelm the body's
defense systems.  The interesting part of this is, temperature change
will not make you ill initially, but, it can lower your body's ability
to defend itself against viruses or bacteria.

Soooo, looking at this example, one would think that if fish are like us
to some small extent they should be able to handle temperature changes.
And, from my experience, they do.

Ok, but, fish are not warm blooded(Endotherms, like us).  Fish are cold
blooded(ectotherms) Well, this is true.  Yet, can cold blood and warm
blood make that much of a difference in temperature tolerances?  
Warm-blooded creatures, like mammals and birds, try to keep the inside
of their bodies at a constant temperature. They do this by generating
their own heat when they are in a cooler environment, and by cooling
themselves when they are in a hotter environment. To generate heat,
warm-blooded animals convert the food that they eat into energy.  
Cold-blooded creatures take on the temperature of their surroundings.
They are hot when their environment is hot and cold when their
environment is cold. In hot environments, cold-blooded animals can have
blood that is much warmer than warm-blooded animals. Cold-blooded
animals are much more active in warm environments and are very sluggish
in cold environments. This is because their muscle activity depends on
chemical reactions which run quickly when it is hot and slowly when it
is cold. A cold-blooded animal can convert much more of its food into
body mass compared with a warm-blooded animal. 

What does this mean?  Something interesting happens here.  A
disadvantage to being warm-blooded is that warm-blooded bodies provide a
nice warm environment for viruses, bacteria and parasites to live in.
Mammals and birds tend to have more problems with these infections than
do reptiles and fish, whose constantly changing body temperatures make
life more difficult for these invaders. However, an advantage of this is
that mammals and birds have developed a stronger immune system than
cold-blooded animals.

A cold blooded reptile or fish immune system is more efficient when the
animal is warmer.  This can be seen when treating fish for ick. The
first thing that helps is to elevate the tank temperature.  This forces
the bacteria to replicate faster, but, it also offers the fishes immune
system a chance to go into high gear to fight infection too. However,
since bacteria probably grow more slowly in lower temperatures, cold
blooded animals sometimes intentionally lower their body temperatures
when they have an infection. This is proven out in studies of disease
control in axolotls.  Diseased axolotls can be placed in a refrigerater
and cooled to near freezing and they seem to heal quicker than if left
at higher temperatures.  So, you can see cold blooded animals walk a
thin line as to which is better, cooler temperatures or warmer ones.

The key to the fish and axolotl temperature impact is the duration of
the temperature (Hmmmm, sounds like my kids again).  Axolotls kept as
near freezing do not eat.  How long can they go without eating?  Long
enough to fight off an infection if they are in reasonable
condition.....but, not for significantly long durations.  How long can a
fish go at elevated temperature?  Long enough to allow ick medication to
kill off the parasite, but, they cannot live at elevated temperatures
near as long as they can at cooler temperatures.

Ok Clay, what is the point of all this?  In short, the health of the
subject and duration of the temperature change are the keys to the
potential adverse impact of environmental temperature variance to the
subject.  Temperature fluctuations over short periods of time (swimming
through thermoclines) can be accommodated by fish with no adverse
impact.  This is only true provided the fish are healthy to begin with.
If a fish is diseased, temperature fluctuations can either improve or
degrade the subject's condition.  Without trial and error, I am not sure
if it can be predicted which way the diseased subject will sway when the
temperature is changed.

There ya have it.....my 5 cent answer to a $5 question.

Clay




-----Original Message-----
From: DELPHILABS@aol.com [mailto:DELPHILABS@aol.com] 
Sent: Wednesday, March 30, 2005 10:42 PM
To: gsas-member@thekrib.com
Subject: [GSAS-Member] Fish & temperature?


When I am scuba diving with fish, I am always shocked at temperature and

salinity changes as I am swimming around.  In some places the water
shimmers 
like oily water because fresh water is mixing with salt.  In some
places I enter 
very cold thermoclines and in others the water feels like  bathwater.
The 
fish are swimming right alongside me.
 
How is it that we are so cautious about temperature changes in the
aquarium  
when they are the norm in nature?  I can see the concern over long term

temperature levels, but during water changes etc, I wonder if it really
much of  an 
issue.  
 
I'd appreciate the list's thoughts.
Thanks!
Keith
 
PS: recently back from diving in Belize.
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