1. Oncorhynchus mykiss Rainbow trout
Family: Salmonidae (Salmonids)
Order: Salmoniformes (salmons)
Class: Actinopterygii (ray-finned fishes)
Oncorhynchus mykiss     Rainbow trout    

2. External Anatomy
Head
Trunk
Tail

3. External Anatomy Dorsal Fin Adipose Fin Caudal or Tail Fin
Pectoral Fins
Anal or Ventral
Fin
Pelvic Fins
Pectoral fins: The pectoral fins act as brakes and help the fish turn left and right.
Caudal fin: The caudal fin or tail fin is the biggest fin. It provides the “push” for the trout to start moving and also acts as a rudder for steering through the water.
Pelvic fins: The pelvic fins help the fish move up and down.
Anal, adipose and dorsal fins: These fins are used for swimming and balance.

4. External Anatomy Operculum Eye Scales Mouth Lateral Line
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Lateral Line
Eye
Operculum
Mouth
Scales
Lateral line: Runs from the head of the fish to the tail. It detects vibrations or waves in the water. This helps keep the trout from bumping into things and helps the fish sense danger.
Eyes: The pupils have a slight triangle shape which helps the trout see above, in front and below its body.
Scales: Protect the fish. They grow as the fish grows.
Mouth: Trout use their mouths to grab food and feel things.
Operculum: This is a hard plate that covers the delicate gills

5. Eye
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Trout can see things both near and far away. The large pupils let as much light as possible enter the eye.

6. Lens
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The lens in the eye moves around and allows fish to focus on objects.

7. External Anatomy Nostril or Nare Teeth
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Nostril or Nare
Teeth
The nare is a closed sac. It helps the fish to smell odors.
Teeth are found along the upper and lower jaws. They grasp and hold onto prey.

8. Mouth Food passes through the esophagus to the stomach.
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Food passes through the esophagus to the stomach.
Gill rakers strain particles out of the water to keep the gills from getting clogged and injured.
The tongue has teeth which help to hold onto prey.

9. Expose Gill Tissue
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Cut off operculum to show the gill.

10. Gills Gill arch Gill filaments
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Gill filaments
Gill arch
Water is taken in through the mouth and passes over the gills. The gills take in oxygen and release carbon dioxide.

11. Carefully cut a flap to expose the internal organs.
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Carefully cut a flap to expose the internal organs.

12. Internal Anatomy Spleen Gall bladder Liver Heart Kidney Pyloric caeca
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Spleen
Gall bladder
Liver
Heart
Kidney
Pyloric caeca
Stomach
Swim bladder
Vent: is the opening through which eggs or sperm (milt) pass during spawning.

13. Kidney
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Kidney
The kidney filters waste from the blood stream and also makes blood. Two canals carry waste from the kidneys to the bladder. From the bladder, the waste passes to the outside through a hole called the vent.

14. Swim Bladder This is an inflated swim bladder .
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This is an inflated
swim bladder .
The swim bladder is like a balloon. It allows the trout to float and move up and down in the water. To fill the swim bladder, fish gulp and swallow air. Fish “burp” to get air out of the swim bladder.

15. Stomach: This is where food is mixed with hydrochloric acid and mucous and then passes to the intestines.
Digestion
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Stomach
Fat
Intestine

16. Path of Digestion Mouth Esophagus Cardiac stomach Vent Pyloric stomach
Intestines
When a trout eats, both food and water enter the mouth. Water is directed to the gills, and food goes to the esophagus which leads to the stomach. Food moves through the stomachs into the intestines and is eliminated out the vent.

17. Cardiac Stomach
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Digestion of food starts in the cardiac stomach. Acid secreted by glands activate enzymes that digest protein.

18. Pyloric Stomach
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The pyloric caeca act like a small intestine. They release digestive juices needed to break down food and absorb nutrients into the blood stream .
Pyloric caeca

19. Liver
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The liver produces bile which is stored in the gall bladder. Bile breaks down fat.

20. Gall Bladder
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The gall bladder is connected to the liver and stores bile made by the liver.

21. Spleen
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The spleen makes and stores blood.

22. Heart and Gills Compare the location of the heart to the gills.
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Compare the location of the heart to the gills.
Why is this important?
Gills
Heart

23. Close up of Heart
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Ventricle
Atrium
Bulbus arteriosus

24. Heart
The heart consists of two chambers, the atrium that receives the blood and the ventricle that pumps the blood to the body. The blood first passes through the gills where it picks up oxygen, then circulates through the body to the organs where nutrients, gases and wastes are exchanged.
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Ventricle
Atrium
Bulbus arteriosus

25. Brain Cerebellum Medulla oblongata Optic lobes
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Medulla oblongata
Cerebellum
Optic lobes
The brain is the control center of the fish. All sensory information is processed by the brain. Automatic functions (such as breathing) and higher behaviors ("Should I eat that critter ?") happen in the brain.