ventral surface
Physical Description
Perch are thin and oval-shaped, tapering at the front and back. This is
an ideal shape for a fish as it helps water rush over it and therefore
makes it move through the water faster and easier. The ventral surface
(bottom) of the fish is lightly coloured and the dorsal surface (top) is
darkly coloured for protection. The perch has many fins that serve various
purposes, such as balance and movement. The fish's entire body is covered
in scales to protect itself and prevent moisture from entering or escaping.
Along the sides of the perch is a line of pitted scales called the lateral
line. The perch has eyes, nostrils, a mouth, operculum, urogenital opening,
and an anus opening.
ventral surface
Roles of Features
Dorsal Fins- help the fish steer and stay upright
Pectoral Fins- keep the fish moving forward or backward
Pelvic Fins- help the fish steer forward and stay upright
Anal Fin- acts as a rudder, steering the fish in a straight line and keeping
its balance
Caudal Fin- helps the fish go forward
Lateral line- senses water pressure changes
Eyes- can detect movement but can only see objects that are nearby
Nostrils- used to smell
Mouth- allows water to enter
Operculum- covers the gills and helps in breathing
Urogenital opening- opening where egg or sperm cells pass
Senses
The five senses are sight, hearing, touch, scent, and taste. The perch
has its eyes which are used for seeing. The perch can not hear or touch,
but can feel changes in water pressure because of the lateral line. It
uses its nostrils for smelling and its mouth for tasting.
Locomotion
Fish spend their entire lives in water and adapt well to the environment.
Their only way of moving is by swimming and their bodies are designed so
that they meet little or no resistance when they are swimming. When the
perch is swimming, an internal gas-filled sac enables it to change its
depth.
Survival
The perch has many ways of protecting itself from preditors. The most obvious
is the colouring of the different surfaces of the fish. The dorsal (top)
surface is darkly coloured so that to preditors above the fish looking
down, the fish is blending in with the dark bottom. The ventral (bottom)
surface is lightly coloured so that to the preditor below the fish looking
up, the fish is blending in again with the light and the sky.
Another method of protection is the slimy substance on the fish's skin.
This prevents the fish from being grasped easily.
Gathering Food
The perch's teeth are sharp and pointed, designed for griping its food
in its mouth.