The Perch. So Shady, So Fishy

Daniel Liao 4/9/14 PAP BIO-PERIOD 6

Objectives

Students will be:

  • Learning about the external and internal anatomy of a perch.
  • Focusing on the organs, structures, and functions of the circulatory system.
  • Understanding the ecological role of the perch.

The Taxonomy of a Perch

  • Kingdom: Animalia - eukaryotic, multicellular
  • Phylum: Chordata-possesses a notochord
  • Class: Osteichthyes- bony fish
  • Subclass: Neopterygii- lighter skeleton, more powerful jaws
  • Order: Perciformes - bony fish, vertebrate
  • Family: Percidae - operculum, 'armoured' head
  • Genus: Perca
  • Species: flavescens (Yellow Perch), fluviatilis (European Perch), schrenkii (Balkhash Perch)

What's so fishy about the Perch?

Judged by its powerful jaws, the perch is considered a carnivorous fish, preying upon smaller fish, water insects, larvae, crayfish, and worms. The perch is characterized by a medium-sized (7-10 inches), rounded body, as well as having ctenoid scales. The perch is commonly a gamefish, and can be also kept as a pet. Due to its aggressive and predatory nature, however, it would be recommended that the perch be kept away from smaller fish and smaller aquatic animals. The perch, although a predatory fish, is not the top predator in its ecosystem. The perch is considered both as prey and as predator, as it is known to be eaten by larger fish (Catfish, bass), birds (Herons, Gulls, etc), and by other fish-eating animals (younger perch have been prey to turtles, bullfrogs, and the like). Perch can be found in quiet ponds, lakes, and slower rivers.

Evolutionary History of the Perch

Scientists, by analyzing the ancestors of perch-like fish, have found that in the development of the subclass Neopterygii, fish, like the perch, developed lighter scales and skeletons, being able to swim faster, and with greater agility. Another evolutionary trait acquired by those of the subclass Neopterygii is extremely powerful jaws, well suited for carnivorous fish who feed on crustaceans and smaller fish. Although many fish quite similar to perch have developed, and even have been given a similar name, true perch must be of the family Percidae. Perch also have tougher heads, well scaled and have developed protective bony coverings known as the operculum to cover and protect the gills. An evolutionary chart of fish can be found below. Perch are classified under the infraclass Teleostei. Note that Perch stem from the Neopterygii subclass.
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Human Impact

As perch are considered by many to be quite tasty, with a 'mild, tangy flavor', perch are prized by commercial fishermen, and are often fished for sport. As perch are carnivorous, and often hunt in large schools, they are easy to catch, and can be sometimes caught by accident. In the fishing industry, not only are perch good fish to catch, they're good as bait too. As perch are a regular food source for larger fish, which can be even more sought after by fishermen, many fishing lures mimic perch. A relative of the perch, a perchlike fish belonging to the class Perciformes, the Nile Perch is a massive fish, capable of reaching 2 meters in length, and weighing over 440 pounds. The Nile Perch is a top predator of its ecosystem along the Nile River, and Congo River Basin. Originally native to only the Congo River Basin, the Nile Perch was introduced to the Nile in 1900. This led to the destruction of 150-200 indigenous fish species, earning the Nile Perch a spot on the IUCN's Invasive Species Specialist Group's top 100 worst invasive species list.

A Detailed Look at, and Inside our Fishy Companion

In the dissection lab conducted in class, the perch was examined internally for its circulatory system. The circulatory system of a perch is a single-loop system with low pressure that allows for the blood of the perch to flow in only one direction. The perch's heart contains only one ventricle and one atrium, which consists of two chambers. When levels of oxygen in the blood are low, they are pumped through the heart, receiving fresh oxygen from the gills, the perch's equivalent to human lungs. After passing the oxygen on to the necessary body parts, the blood is then sent back to the heart. The parts of the perch's circulatory system are as follows:

Heart: The heart is the muscular organ that pumps blood in the perch, in a one-direction loop.

Atrium: The atrium are the chambers in the top of the heart, which receive incoming blood from the heart.

Ventral Aorta: This part circulates blood to the gills, and then from there on out to the rest of the perch's body.

Dorsal Aorta: This part is similar to the Ventral Aorta, but instead circulates blood from the heart to the organs.

Jugular Vein: The Jugular Vein is a large blood vein that carries blood to and from the head or face.

Liver: The liver is an organ that functions to filter blood.

A video of a full perch analysis and dissection of a perch can be found below.

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Perch Dissection