What Are the Body Part Definitions of a Perch Fish?

Basic Body Structure

• The head of a perch's body is attached directly to the trunk of the fish. It has no neck. The trunk ends at the anus and takes up roughly two-thirds of the perch's body. The tail starts at the area behind the anus and makes up the hind part of the fish. The spinal cord is attached to the perch's head and fins and runs laterally through the body of the fish. The skull of the perch has hinged, bony jaws that are lined with teeth.

Fins

• The pectoral fins are located at the front of the perch near the gills. The pelvic fins are below the pectoral fins and located lower on the fish near the belly of the animal, which is lighter in color than the rest of the perch. The largest anterior or front dorsal fin has spines that tilt up and down and can lift up to extend the fin to its full length, and the posterior or back dorsal fin is smaller with soft, fixed rays that do not move. The anal fin is located behind the anus and has a single sharp spine amongst its soft rays. The caudal or tail fin is located at the end of the vertebra or spine and is used by the fish to propel itself through the water.

Lateral Line

• The perch has a thin lateral line that extends from the operculum, or gill cover, across the middle of the fish's side, all the way to the caudal fin. The lateral line has different kinds of scales on it than the rest of the perch's skin. It is a sensory organ of the fish that detects vibrations in the water caused by the movement of objects or other animals around them. The other sensory organs of the fish are its eyes and swim bladder.

Swim Bladder

• The swim bladder or air bladder is an internal organ that is unique to fish. The bladder controls the depth that the perch is swimming at in the water. When the bladder inflates, the perch rises to a higher depth in the water. When the bladder deflates, the perch descends to the bottom of the lake. The air bladder also stabilizes the fish and keeps it upright in the water at all times.

Gills

• The nostrils and mouth of the fish allow water to enter the animal's gills. A perch "breathes" in water by gulping water in through its mouth and pumping it past four pairs of gills in the gill chamber. The gills absorb dissolved oxygen in the water and transfer it to the fish's blood. Perch have gill chambers on both sides of its head. Every gill has two rows of flesh-like filaments attached to a gill arch located in the gill chamber. The gills are covered by a flap of bone called a gill cover.

Digestive System

• The digestive system of a perch consists of a stomach, intestine, liver and kidneys. The stomach of the perch is located underneath the spinal cord on the bottom or belly of the fish between the caudal and anal fins. The urogenital opening is the outlet from the kidneys and the ovary of the fish.

Muscle Structure

• Skeletal muscles or body muscles make up the perch's flesh. They are attached to the spinal cord and ribs and they move the bones and fins of the animal. Skeletal muscles are arranged behind one another in broad vertical bands that are called myomeres. Myomeres are controlled by separate nerves that allow the fish to bend and move its head and tail. When a perch has its skin removed, the myomeres are clearly visible to the eye. Heart muscles and smooth muscles work together to pump the heart. The smooth muscles are attached to the fish's stomach and intestines and facilitate digestion.