Date: Mon Mar 1 19:56:11 1999
Posted By: Rob Campbell, PhD Candidate, Biological Oceanography, University of British Columbia
Area of science: Zoology
ID: 920234819.Zo
Message:
Hi Pablo-
No, strictly speaking, fish do not adjust their depth the same way
that submarines do (by taking in and pumping out volumes of water), but
they do use the same mechanism- that is, by adjusting their buoyancy. They
can create buoyancy (an upward force, or "lift") a couple of ways:
Dynamic Lift is created by creating lift through
motion. A good analogy of this is when you stick your arm out of a fast
moving car and allow it to "fly". Negatively bouyant fish (like sharks)
must swim constantly, or they'll sink.
Static Lift is created by creating buoyancy through
density differences- this is the same mechanism a submarine uses (but
submarines use liquid water while fish use gas). Buoyancy inside the fish
is done with the swim bladder and regulated a couple of ways:
1. They can suck in air at the surface, and regulate their buoyancy
it by "burping" it out, or
2. They can create their own gas, usually oxygen, with a gas
gland. By secreting oxygen, or reabsorbing it into their blood,
fish alter their volume slightly, and thus their buoyancy.
Fish with sealed swim bladders (called
physoclistous swim bladders) have to be careful, because
their swim bladder will burst if they rise too quickly- the reduction in
water pressure with decreasing depth causes the swim bladder to expand, and
so the pressure must be decreased by reabsorbing the gas. If the swim
bladder isn't sealed, the fish can simply "burp" out the extra
pressure.
Hope that answers your question,
Rob Campbell, MAD Scientist
Current Queue |
Current Queue for Zoology |
Zoology archives
Try the links in the MadSci Library for more information on Zoology.
MadSci Home | Information |
Search |
Random Knowledge Generator |
MadSci Archives |
Mad Library | MAD Labs |
MAD FAQs |
Ask a ? |
Join Us! |
Help Support MadSci
MadSci Network,
webadmin@www.madsci.org
© 1995-1999. All rights reserved.