FISH DISSECTION                NAME____________________

Objectives:      dissection   perch

south dakota walley spawning with game fish and parks
Describe the appearance of various organs found in the fish.
Name locate and identify the organs that make up various systems of the fish
Compare and contrast fish anatomy to other dissections.
Contrast and compare a fish's body parts to a human's.

Safety goggles, dissecting pins, gloves, forceps, lab apron, scissors, paper towel, scalpel, water, dissecting probe, preserved fish, hand lens, dissection tray.

In this lab, you will dissect an fish in order to observe the external and internal structures of fish anatomy

Vertebrate Classification
        Kingdom Animalia
        -----Phylum Chordata
        ----------Subphylum Vertebrata

Class Examples
Agnatha Jawless fishes; lamprey & hagfish
Chondrichthyes Cartilage fish, sharks and rays
Osteichthyes Bony fish; salmon, catfish, goldfish
Ray-finned fish are built for swimming. Instead of legs, they have fan-like parts called FINS . Fish also have bony skulls to protect their brains. They have VERTEBRA which protect the nerve cord running through them, and they have strong muscles attached to their bones so they can swim well. Bony fish have a swim bladder filled with air, which keeps them from sinking to the bottom.  The lateral line is sensory it feels vibration from noise and also pressure from the water depths.  It tells the swim bladder how deep it is so the fish can adjust the gasses in the swim bladder and float at different levels. It helps them float at any level in the water. 
     Fish have a two chambered heart which is very inefficient.   Oxygenated blood mixes with deoxgenated blood.  In a 4 chambered heart like mammals and birds have the blood does not mix so it is more efficient thank the fish heart.
Many fish have scales, hard plates which are part of the skin. fish have gills. Gills are body parts which allow fish to breathe under water. The operculum a bony flap, covers and protects the gills. All fish are eXtothermIC (ectotherms) so the inside temperature of their bodies is the same as the temperature of the water around them. 
    There is oxygen in tiny bubbles throughout the water in the ocean. Fish take in this oxygen-filled water through their mouths. The water passes over the gills. In the gills is blood, full of tiny carbon dioxide bubbles. Because the gills are so thin, the oxygen can go into the blood and the carbon dioxide goes out into the water. Then the water passes out of the body of the fish.
    Fish reproduce  it is called spawning.  The females have soft  eggs. The female fish lays eggs in the water. The male swims over them and fertilizes them with a fluid called milt. Then the eggs are left to hatch on their own. Many eggs do not hatch or are eaten by predators. Yet some survive so more fish can be born.   Fish have mucus to protect them from parasites and bacteria.  Mucus falls off them with the parasites and bacteria as they swim through the water.

a. FISH  PHYLUM   ____________________________________________

b. CARTILAGE FISH CLASS ____________________________________

c. BONEY FISH CLASS _________________________________________

d. JAWLESS FISH CLASS _______________________________________


External features:
1. Feel the fish's skin.  Why do fish have mucus._________________________________________  Use a magnifying glass to see how the scales are arranged.
Why do fish have scales?_________________________________________

3. Look at the color pattern. What is the advantage of a fish  being dark on dorsal side and light on the ventral side?__________________________________?

4. Observe the lateral line. What it is used for?__________________________________ 

5.  How does the lateral line  works?___________________________________________________

6. Observe the shape of the fish.   How this is an advantage?________________________________ 

7. Observe the eye. Note the relatively large size, and the large pupil, hypothesis how important vision is for this animal?__________________________________________________________ 
8.  Is there an eyelid?___________________________

9. Locate the nostrils.  Describe the location and the number of the nostrils._______________  

10. Insert a probe into one of the nostrils. Does the probe enter the mouth cavity?  ______  Why?____________________________

11.  Feel the teeth along the gum margins and on the roof of the mouth. What are the teeth used for?______________________________________________________.

12. Determine the probable use of the tongue.  Does the tongue feel like a human tongue? __________
13. See how wide the mouth can open. Suggest a reason for this?____________________

 The mouth is also used for breathing. In low oxygen conditions, fish can actively pump water over their gills by opening and closing their mouth. 
14. The gills arches can be seen by looking down the fish's mouth and gently lifting up the operculum. Use a probe to separate the arches and explore how they are arranged.  How many arches are there_________
15. Place the fish on its side and look at the operculum, the boney plates which protect the gills. Lift the operculum and look at the gills. Now cut the operculum away at its base, exposing the gills.
16. Remove the one of the gills by cutting the upper and lower attachments of the arch. Look at the gill rakers, the bony projections along the inside curve of the arches. Observe the large surface area provided by the gill filaments, and the thin tissue which allows blood vessels to come into contact with the oxygen in the water. Compare and contrast gills and lungs. 
1. SCALES    
3. NOSTRIL    
6. ANAL FIN    
8. EYE    


10. MOUTH    
12. CAUDAL FIN    
13. ANUS    


 Internal Organs:
1. WHAT IS AN ECTOTHERM?_____________________
2. Carefully cut the fish by inserting a scissors  point into the anus and open  to the bottom of the mandible (jaw).  Be careful not to cut into the fish's internal organs.  Cut away the flap of skin and look for fat deposits (orange and greasy looking), which are found around the stomach.
What is the importance of fat _________________________________________________________________

3. Locate the swim bladder. It is made of very thin tissue and is located in the upper body cavity, below the kidneys.  What is its function? ____________________________________________.

4. Locate the male reproductive organs (testis) will be flaccid white or orange tissue near the intestines. If you have a female locate the ovaries.  Eggs may or may not be noticeable in females. Both will vary in size depending on maturity of the fish.  Why do fish produce so many eggs.  _______________________

5. Put the fish on its dorsal side and find the kidneys, located just under the backbone. They are thin, dark in color, and run the whole length of the body cavity.  What is their function ___________________

6. Put the probe through the mouth and into the esophagus to show the beginning of the route.  Why is the esophagus so elastic________________________________________________________


7.  Does the stomach have any food in it? ____________  If so make a small incision and observe the prey.  The first area of the stomach is called the cardiac stomach; this is where digestion begins. Notice the different kinds of tissue that make up the stomach. The pyloric stomach is that portion from which the pyloric ceaca project. It begins at the bend below the cardiac stomach, and is made of different tissue. Discuss how the stomach area is increased by the pyloric ceaca. How does this improve the function of the stomach? __________________________________________________

8. The intestines provide the last chance to extract nutrients from food.  Why is the intestine so long? ___________________________________________  Notice the network of blood vessels which are used for nutrient exchange.  Follow the intestines to the anal opening where waste products are eliminated.
9. The spleen will be seen by lifting the stomach. It is a reddish organ found at the end of the cardiac stomach. What does it do?______________________________________________________________.

10. The liver is just in front of the stomach.  The liver produces bile which is stored in the gall bladder.  What does bile digest?  _________________.   The gall bladder is a mass of darker tissue on the liver.

11. A fish's heart is between the gills.   Identify the atrium and ventricle.  How many chambers are there ____________.    The fact that the gills, heart and liver are so close together is no coincidence. Blood pressure is best near the pump (heart). Blood is filtered by the liver, and absorbs oxygen from the gills; both are vital functions.
12. Cut through the fish to expose the back bone and muscles. Observe arrangement of the muscle masses. (This is the part of the fish we eat.)
13. Observe the  growth rings on the scales.   Try to remove some of the scales so you can look at the rings.
14.  Explain why the fish has an inefficient heart_____________________________________.

15.  Dissect the brain
16.  Dissect out the lens of the eye.

circulatory system
1. HEART - pumps blood
2. VENTRICLE - pumps blood to body
3. ATRIUM - pumps blood to ventricle

Excretory system
1. KIDNEY - filters liquid waste

nervous system
1. BRAIN - controls body
2. SPINAL CORD - sends and receives messages

3. SWIM BLADDER - allows fish to float at any level
4. LATERAL LINE - senses vibrations and pressure
5. NOSTRIL - smell
6. EYE - vision

digestive system
1. MOUTH - opening for food
2. esophagus - forces food from mouth to stomach

3. STOMACH - breaks down food
4. GALL BLADDER - stores bile made in liver
5. bile- breaks down fat

6. LIVER - makes bile and digestive enzymes detoxes you
7. spleen - filters out old and dead red blood cells,  dumps them in the intestine.  that is why your poop is reddish brown   6 million per second.
- breaks down and absorbs food
. ANUS - opening for wastes
10. fat - stores food, cushions organs, insulates ( helps keep warm)

reproductive system
1. GONADS - makes sex cells
2. ovary - makes eggs
3. testis - makes sperm

respiratory system
1. GILLS - breathing oxygen and carbon dioxide diffuses here

skeletal system
1. VERTEBRAE - protects spinal cord
2. SCALES - protect skin
3. ANTERIOR DORSAL FIN - protection
4. POSTERIOR DORSAL FIN - protection
5. PECTORAL FIN - steering and movement
6. PELVIC FIN - steering and movement
7. ANAL FIN - steering
8. CAUDAL FIN - movement
9. OPERCULUM - protects gills



1. HEART    
2. KIDNEY    
4. ANUS    
5. GONADS    
6. LIVER    
7. BRAIN    
9. GILLS    
10. STOMACH    
13. ATRIUM    




Use your book (page764-765) to reference the anatomy of the fish. Find each of the organs below and color code them to the fish according to the key below.

Caudal Fin (blue) Gills (red) Muscles (red)
Anal Fin (pink) Heart (pink) Vertebrae (yellow)
Dorsal Fin (yellow) Stomach (green) Swim Bladder (blue)
Pelvic Fin (green) Esophagus (yellow) Kidney (green)
Pectoral Fin (orange) Liver (brown) Scales (purple)
Operculum (brown) Intestine (blue)  
Lateral Line System (black) Reproductive Organs (orange)  

Fish Scales Tell the Age of a Fish

Look at the image of the fish scale, like a tree, scales show rings that indicate periods of growth. Rings that are farther apart occur when the fish grows well and there is lots of food - in the summer season. Rings that are close together occur when the fish does not get much food and grows slowly. On the scale you can identify the summer growth and the winter growth. (There will be several rings in each).

The core represents the fish when it was first born, as a fry. The rings near the edge are the most recent periods of growth.

Color the summer growth periods green.
Color the winter growth periods blue.

How old is this fish (in years)? _____________________

Fish Parts

Label the parts on the fish.
Then find the names of these parts in the word search.
Words appear across or up and down.
Click here for the answers

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Fish Parts

fish parts


word search

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