The Peculiar Physiology of a Perch

by Kierra Morris

The Perch

The Perch is a the common name for freshwater ray-finned carnivorous fish comprised of the genus Perca of the family Percidae and order Perciformes. The scientific name depends on the type of fish it is from the perch family, Perca flavescens (Yellow perch), Perca fluviatilis (European perch), and Perca schrenkii (Balkhash perch). The perch is a fresh water fish found in small ponds, lakes, streams, or rivers. Naturally, the perch falls into both groups of prey and predator. They prey on live insects, crustaceans, small fish and various other small creatures, their predators are large fish like striped bass, walleye, bluefish and weakfish, their eggs and larvae are eaten by bluegill, copepods and other perch. Some adaptations of this fish are large eyes, because its feeding depends on sight, spines for protection and stiffness in fins, a thin shortened disc-shaped body, making it harder for predators to swallow, and stripes for camouflage protection.

Objectives !

Students will discover the placement of organs and their relationships to one another in a perch. Pictures and diagrams will help students understand the external and internal structures of the perch

Perch Trophic Level

The perch falls into the category of a 'secondary consumer' when looking at marine trophic levels. Even though the perch is a carnivore, it still falls short of being in the strongest domain, mainly due to its size and power. The appetite of a perch ranges from small things like fish eggs or insects, and can reach out as far as eating other perch and species of fish.

3 Types of Perch

Discection of Perch

Gills: organ that fish use to breathe, consisting of a membrane containing many blood vessels through which oxygen passes. Gills are a vital part to a fish's respiratory system, the gills collect oxygen molecules fro the water and then excrete carbon dioxide from the fish's system.

Heart: two chambered organ that pumps blood through the body. The Perch has a closed loop circulatory system, where the heart pumps blood in a circle, to the gills and then back to the heart.

Stomach: The part of the digestive tract between the esophagus and the intestine. During digestion, food is further broken down within the stomach, the food collect in little pocket like pouches called pyloric acid, where enzymes come and help with the digestion process and collect nutrient from the food.

Intestine: part of the digestive system between the stomach and the anus or cloaca that digests and absorbs food. After the food has past through the stomach, the food is further digested and broken down to where nutrients and water can be collected.

Pharynx: the membrane-lined cavity behind the mouth and nose, connecting to the esophagus. The pharynx have opening on either side where gills push out deoxygenated water from the body.

Swim Bladder: a gas-filled sac present in the body of many bony fishes, used to maintain and control buoyancy. Also called the air bladder, also has a secondary purpose, it serves as a resonating chamber to produce or receive sound.

Liver: a large lobed glandular organ in the abdomen of vertebrates, involved in many metabolic processes. The liver plays an important role in digestion, where it releases enzymes to help break down food, store fats and carbohydrates, and helps in the destruction of old blood cells and maintaining nitrogen waste excretion levels.

Esophagus: part of the digestive tract connecting the mouth to the stomach. The esophagus transports and foods and liquids to the stomach, as well as digests and breaks down the food.

Kidney: the blood purifying organ. As well as filtering the blood, it is important in regulating water and salt concentrations within the fish's body. This allows the perch to be able to thrive in fresh water and very low salt concentrations.

A Perch's Circulatory System

The circulatory system of a fish is similar to that of many mammals, it consists of a heart, blood, and blood vessels. What is unique about a Perch's circulatory system is that it is a single circle circulation that is considerably low pressure. You can think of the system going through three easy steps.

1. Oxygen deprived blood goes to the heart to then be pumped through the gills.

2. In the gills, it gathers oxygen molecules, to where it is pumped through the body and its tissues.

3. The now deoxygenized blood circulates back to the heart to start the process over again.

In fish, before the deoxygenized blood reaches the heart, it is carried by the veins into a cavity called the Sinus Venosus.

Circulatory System in Relation to others

The circulatory system of the perch is connected to the respiratory system. When water is taken into the mouth of the fish, it passes over the gill filaments, this is where the gas exchange of oxygen occurs. The blood capillaries in the gill filaments allow the fish to give up carbon dioxide and receive oxygen, where it is then entered into the circulatory system.

Fun Facts!

1. The meat of this species is low in fats and rich in phosphorous, manganese, selenium and vitamin B12.

2. They spawn at the temperature of about (43 to 48) degree Fahrenheit.

3. Perch is found in Britain, Europe, South Africa, Asia and Australia.

Live Dissection

Bony Fish (Perch) Anatomy

Nile Perch Destroying Africa's Ecosystem

Works Cited