Name ___________________________
Date _________ Period 1 2 3 4 5 6
Marine Biology Lab: Fish Dissection
Background:
The fish in the class Osteichthyes have bony skeletons. There are three groups of
the bony fish - ray-finned, lobe-finned, and the lungfish. 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. The perch also has a streamlined 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. Perch have powerful
jaws and strong teeth for catching and eating prey. Perch are primarily bottom feeders. They eat almost anything,
but prefer minnows, insect larvae, plankton, and worms. Perch move about in schools, often numbering in the
hundreds. The scientific name for the yellow perch is Perca flavescens (Perca means "dusky"; flavescens means
"becoming gold colored").
Purpose: To examine the internal and external anatomy of the perch.
Materials: Dissecting pan, dissecting tools, safety glasses, preserved perch
Figure 1: External Perch Anatomy
Procedure:
External Anatomy
1. Rinse your perch.
2. Label the anterior, posterior, dorsal,
and ventral sides on Fig 1.
3. Label the 3 body regions of the perch
– head, trunk, and tail – on Fig 1.
4. Open the mouth and observe its jaws.
Label the upper jaw (maxilla) and the
lower jaw (mandible) on Fig 1.
5. Feel inside the mouth for the teeth.
6. Open the mouth wide and use a probe
to reach back to the gill chamber.
7. Label the eyes and nostrils on Fig 1.
8. Find the lateral line on the side of your perch. Label this line on Fig 1.
9. Observe the different fins on the perch. Locate the pectoral, dorsal, pelvic, anal, and caudal fins. Label
these on Fig 1 and complete Table 2 on fins.
Name of Fin
Spines (Y/N)
Table 2: Fins
# of Fins Location
Function
10. Find the bony covering on each side of the fish's head called the operculum. The opercula cover &
protect the gills. Label these on Fig 1.
11. Use a probe to lift the operculum and observe the gills. Note their color.
12. Use scissors to cut away one operculum to view the gills. Find the gill slits or spaces between the gills.
13. Use your scalpel to carefully cut out one gill. Find the cartilage support called the gill arch and the soft
gill filaments that make up each gill.
Name ___________________________
Date _________ Period 1 2 3 4 5 6
Fig 3
14. Use forceps to remove a few scales from your fish. Observe the scales under the
magnifying glass or microscope. Sketch a scale on Fig 3.
Internal Anatomy
15. Insert the tip of the scissors in the anus and cut toward the head, between the pelvic fins
and just past the pectoral fins. Cut only through the skin, careful not cut any organs.
Continue cutting through skin and muscle as in Fig 4.
16. Carefully lift off the flap of skin and muscle to expose the internal organs in the body cavity.
17. Locate the cream colored liver in the front of the body cavity. Also locate the gall bladder between the
lobes of the liver. Label these on Fig 5.
Fig 4: Cut lines
18. Remove the gall bladder & liver to observe the short esophagus attached to the stomach.
Label the stomach on Fig 5.
19. At the posterior end of the stomach are the coiled intestines. Label these on Fig 5.
20. Find the small reddish brown spleen near the stomach and label this on Fig 5.
21. Below the operculum, are the bony gill rakers. Locate these and them label them on Fig 5.
22. In front of the liver & behind the gill rakers is the pericardial cavity containing the heart. The heart of a
fish only has 2 chambers --- an atrium & and a ventricle. Locate the heart & label it on Fig 5.
23. In the upper part of the body cavity, below the lateral line is the swim bladder. This sac has a thin wall.
Label the swim bladder on Fig 5.
Figure 5: Internal Perch Anatomy
24. Below the swim bladder are the gonads
(testes or ovaries). Label them on Fig 5.
25. Find the two long, dark kidneys in the
posterior end. Label the kidneys in Fig 5
26. Wastes exit the body through the anus
located on the ventral side of the perch.
Label the anus on Fig 5.
Questions:
1. Are both jaws of the fish equally
movable? Explain your answer.
2. Does the perch have eyelids?
3. How many gills are located on each side of the perch? What covering protects them?
4. The tail end has no organs; it’s all muscle. Why do you think that is?
5. Explain how gas exchange occurs at the gills.
6. Which fin was the largest? What other difference do you notice in this fin compared to the others?
7. What is the function of the lateral line?
8. Describe how the scales are arranged on the trunk & tail of your fish.
9. What is the function of the swim bladder? Explain how it works.
To learn more, check out:
http://bioweb.uwlax.edu/zoolab/Table_of_Contents/Lab-9b/Perch_Mount_1/perch_mount_1.htm