NAME:______CLASS:______

Perch Dissection

The fish in the class Osteichthyes have bony skeletons. There are three groups of the bony fish --- ray-finned fish, lobe-finned fish, and the lung fish. The perch is an example of a ray-finned fish. Its fins have spiny rays of cartilage &/or bone to support them. Fins help the perch to move quickly through the water and steer without rolling. Each of the perch’s five fin types is specialized for a different function. Dorsal: Located on the fish's dorsal side (top). Help stabilize the fish and aid it in sharp turnsPectoral: Located on the fish's left and right sides. Allow the fish to control up and down movement.Pelvic: Located on the fish's ventral (bottom) side, below the pectoral fins. Control the direction of movement.Anal: Located on the fish's ventral side, further towards the tail than the pelvic fins. Stabilizes movement and help in sharp turns.Caudal: a.k.a. the tail fin. Provides a powerful forward thrust to propel the fish through water.

The perch also has a streamline body shape that makes it well adapted for movement in the water. All ray-finned fish have a swim bladder that gives the fish buoyancy allowing them to sink or rise in the water. The swim bladder also regulates the concentration of gases in the blood of the fish. (Similar to the job performed by the lungs in humans)

Perch have powerful jaws and strong teeth for catching and eating prey. Yellow perch are primarily bottom feeders with a slow deliberate bite. They eat almost anything, but prefer minnows, insect larvae, plankton, and worms. Perch move about in schools, often numbering in the hundreds.

Procedure (External Anatomy):

  1. Obtain a perch & rinse off the excess preservative. Place the perch in your dissecting pan.
  2. Label the anterior, posterior, dorsal, and ventral sides of the perch on Figure 1.
  3. Use a string and ruller to determine the total length, fork length, and girth of your fish. Record this in Table 1.
  1. Locate the 3 body regions of the perch --- head, trunk, and tail. Label these on Figure 1.
  2. Open the perch's mouth and observe its bony jaws. Locate and label the upper jaw or maxilla and the lower jaw or mandible.
  3. Feel the inside of the mouth for the teeth. Locate & label the tongue & teeth on Figure 1.
  4. Open the mouth wider and use a probe to reach back to the gill chamber.
  5. Locate the nostrils and label on Figure 1.
  6. Locate and note the location of the eyes. Label on Figure 1.
  7. Find the bony covering on each side of the fish's head called the operculum. The opercula cover & protect the gills. Label these on Figure 1.

Figure 1 - External Perch anatomy

  1. Use a probe to lift the operculum and observe the gills. Note their color.

Figure 2 - Gill Structure

  1. Observe the different fins on the perch. Locate the pectoral, dorsal, pelvic, anal, and caudal fins. Note whether the fin has spines. Label these on Figure 1 and complete Table 2 on fins.

Table 2 - Fins

Name of Fin / Spines
(yes or no) / Number of Fins / Location / Function
Pectoral
Dorsal
Pelvic
Anal
Caudal
  1. Locate the anus on the perch anterior to the anal fin. In the female, the anus is in front of the genital pore, and the urinary pore is located behind the genital pore. The male has only one pore (urogenital pore) behind the anus. Determine the sex of your perch.
  2. Find the lateral line on the side of your perch. Label this line on Figure 1.
  3. Use forceps to remove a few scales from your fish. Observe the scales under the magnifying glass. Sketch a scale on Figure 3.

Figure 3 - Structure of a Scale

  1. Count the growth rings on your scale to tell the age of your fish. (Hint: each ring represents one year's growth.)

Use the diagrams below to observe the internal anatomy of a perch and answer the questions below:

Male Perch Female Perch

Figure 4- Internal Perch Anatomy

17. Label the gills, heart, liver, stomach, intestine, and swim bladder on Fig. 4

18. How is the swim bladder similar to our lungs? What other function does the swim bladder provide for the perch?

______

19. List the organs you see that are associated with the breaking down and absorption of food.

______

20. Based on the organs you labeled, what body systems does the perch appear to have?

______

21. Name a structure you see on the perch that you think it uses to respond to its environment and explain how?

______