Understand The Basics Of Fish

It will be wise to learn something about fishes andvertebral column or "backbone", with a very
their requirements if you plan on setting up ancomplicated skull at the front end; behind the skull
aquarium.there are shoulder-bones supporting a pair of pectoral
Breathingfins, corresponding to our arms, and beneath the
Fish take in water through the mouth; they do notabdomen there is a pair of pelvic fins supported by
drink it, however, but pass it out backwards throughinternal bones, representing our legs.
the gill-openings at the sides of the head, under theThe latter are sometimes called ventral fins, but this
bony gill-covers. As it goes through it bathes the gills,is not a good name, because the word ventral, when
which are so constructed that they can take oxygenapplied to fishes, means on the lower side of the
out of the water and get rid of carbon dioxide inbody, and can be applied also to the anal fin, which
exchange. The gills, then, are their breathing organs;lies below the tail, and is single. On the back, in the
they have no lungs. But the process of breathing ismiddle line of the body, is the dorsal fin, sometimes in
otherwise much like ours, and if there is not a propertwo parts. At the end of the tail is the caudal fin; this
supply of oxygen in the water, they will sicken andis often called "the tail" by non-aquarists, but should
die.at the worst be called the "tail-fin".
The oxygen is dissolved in the water, and the carbonSenses
dioxide given off, through contact with the air at theA fish is provided with a brain, simpler than ours, but
surface.nevertheless more efficient than some people realize;
Thus it will be understood that if the surface area isit displays intelligence, and is capable of learning. It has
too small the water will become charged with carbongood eyes and a keen sense of smell. The general
dioxide, and there will not be room for replacementplan of the nervous system is similar to ours, though
of the oxygen when it is used by the fish.again less complex, and it is well to remember that a
The oxygen that the fish breathes is passed into thefish feels pain and may be shocked. Tapping on the
blood circulatory system, and so to the tissues,glass, or sudden knocks on the frame of the
where it is eventually combined with elements of theaquarium, should be avoided, for it has a very
digested food for the production of energy andstartling effect on the fishes.
growth (metabolism). The results of this combinationAlong the side of a fish is a series of very sensitive
are largely carbon dioxide and water, which have toorgans, which are usually visible as a line formed by
be eliminated. The former is breathed out, and thetubes in the scales. This is the lateral line, which in
latter excreted by way of the kidneys. This is alleffect is the outer ear of the fish. It is sensitive to
much the same as the process in higher animals,pressure-waves and vibrations in the surrounding
including ourselves, for the organization of the bodywater, and conveys them to the brain. There is an
of a fish is very similar to ours, though a little simpler.inner ear surprisingly like our own, but concerned
Finsmainly with balance, so far as we can tell.
Fish are the lowest true vertebrates, and thereforeThere is of course much more that can be learned
can be compared with our earliest ancestors. Theyabout fish, but this information will get you off to a
have a bony skeleton, consisting of a jointedvery good start.