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Fish are animals that are
cold-blooded, have fins and a backbone. Most fish have scales
and breathe with gills. There are about 22,000 species of fish
that began evolving around 480 million years ago. The
largemouth bass illustrated above has the typical torpedo-like (fusiform)
shape associated with many fishes.
Fins are appendages used
by the fish to maintain its position, move, steer and stop.
They are either single fins along the centerline of the fish,
such as the dorsal (back) fins, caudal (tail) fin and anal fin,
or paired fins, which include the pectoral (chest) and pelvic
(hip) fins. Fishes such as catfish have another fleshy lobe
behind the dorsal fin, called an adipose (fat) fin that is not
illustrated here. The dorsal and anal fins primarily help fish
to not roll over onto their sides. The caudal fin is the main
fin for propulsion to move the fish forward. The paired fins
assist with steering, stopping and hovering.
Scales in most bony fishes
(most freshwater fishes other than gar that have ganoid scales,
and catfish which have no scales) are either ctenoid or
cycloid. Ctenoid scales have jagged edges and cycloid have
smooth rounded edges. Bass and most other fish with spines have
ctenoid scales composed of connective tissue covered with
calcium. Most fishes also have a very important mucus layer
covering the body that helps prevent infection. Anglers should
be careful not to rub this "slime" off when handling a fish that
is to be released. (See
Scales
for more).
In many freshwater fishes
the fins are supported by spines that are rigid and may be quite
sharp thus playing a defensive role. Catfish have notably hard
sharp fins that anglers should be wary of. The soft dorsal and
caudal fins are composed of rays, as are portions of other
fins. Rays are less rigid and frequently branched.
The gills are the
breathing apparatus of fish and are highly vascularized giving
them their bright red cover. An operculum (gill cover) that is
a flexible bony plate protects the sensitive gills. Water is
"inhaled" through the mouth, passes over the gills and "exhaled"
from beneath the operculum.
Fish see through their
eyes and can detect color. The eyes are rounder in fish than
mammals because of the refractive index of water and focus is
achieved by moving the lens in and out, not distorting it as in
mammals.
Paired nostrils, or nares,
in fish are used to detect odors in water and can be quite
sensitive. Eels and catfish have particularly well developed
senses of smell.
The mouths shape is a good
clue to what fish eat. The larger it is the bigger the prey it
can consume. Fish have a sense of taste and may sample items to
taste them before swallowing if they are not obvious prey
items. Most freshwater fishes in Florida are omnivorous (eating
both plant and animal matter). Some are primarily piscivorous
(eating mostly other fish). The imported grass carp is one of
the few large fishes that are primarily herbivorous (eating
plants). Fish may or may not have teeth depending on the
species. Fish like chain pickerel and gar have obvious
canine-shaped teeth. Other fish have less obvious teeth, such
as the cardiform teeth in catfish which feel like a roughened
area at the front of the mouth, or vomerine teeth that are tiny
patches of teeth, for example, in the roof of a striped bass'
mouth. Grass carp and other minnows have pharyngeal teeth
modified from their gill arches for grinding that are located in
the throat.
The lateral line is a
sensory organ consisting of fluid filled sacs with hair-like
sensory apparatus that are open to the water through a series of
pores (creating a line along the side of the fish). The lateral
line primarily senses water currents and pressure, and movement
in the water.
The vent is the external
opening to digestive urinary and reproductive tracts. In most
fish it is immediately in front of the anal fin.
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