Fish Health and Diseases SS2 Livestock Farming Lesson Note

How Do You Know Your Fish Are Sick?

A good fish farmer is like a doctor; you have to “listen” to your fish even though they can’t talk. Most diseases in a pond happen because the water is dirty, the fish are crowded, or the food is bad.

Signs of a Healthy Fish:

• They swim actively and react quickly if you splash water.
• They have clear eyes and shiny scales.
• They rush to the surface when it is feeding time.

Signs of a Sick Fish:

• Gasping: They stay at the surface “gulping” air (this means they can’t breathe).
• Isolation: A sick fish often swims alone in a corner while others stay together.
• Rubbing: They scratch their bodies against the pond walls.
• Physical Marks: Look for white spots, bleeding fins, or a swollen belly.

Common Fish Diseases (The “Big Three”)

In Nigeria, these are the most common problems you will face in your pond:

1. Fin and Tail Rot (Bacterial)

• What it looks like: The edges of the fins look ragged, torn, or “eaten away.” You might see white or red sores at the base of the tail.
• Cause: Usually caused by dirty water or “bullying” (fish biting each other).

2. Ich or White Spot Disease (Parasitic)

• What it looks like: It looks like someone sprinkled salt or white sugar all over the fish’s body.
• Cause: A tiny parasite that attaches to the skin. It makes the fish very itchy.

3. Fungal Infections

• What it looks like: White, cotton-like growths on the skin or mouth.
• Cause: Often happens after a fish has been handled roughly or wounded. The fungus grows on the wound like mold on bread.

Why Do Diseases Start? (The Stress Factor)

Fish don’t just “wake up” sick. Disease usually happens when the fish is stressed.

Things that stress fish:

1. Overcrowding: Putting 1,000 fish in a tank meant for 200. It’s like living in a room with 50 people—everyone gets sick!
2. Bad Water: High ammonia (from fish waste) or low oxygen.
3. Rough Handling: Catching fish with rough nets or dropping them on the floor.
4. Temperature Change: Moving fish from very cold water to very warm water too quickly.

Prevention (The “Clean House” Rule)

It is much cheaper to prevent a disease than to treat it. Once a disease starts, you might lose half your fish before the medicine works.

• The Quarantine Rule: Never throw new fish straight into your main pond. Keep them in a separate “quarantine” tank for 14 days to see if they are sick.
• Water Management: Change your water regularly. If it smells like rotten eggs, it’s dangerous.
• Liming: As we learned in pond construction, lime helps kill germs in the soil before you start.
• Clean Tools: Don’t use a net from a “sick” pond in a “healthy” pond without washing it with salt or disinfectant first.

Simple Treatments and First Aid

If your fish do get sick, don’t panic. Here is what to do:

1. Stop Feeding: Sick fish don’t eat much. Food left in the water will just rot and make the disease worse.
2. The Salt Bath: Common salt (non-iodized) is a miracle medicine for fish. It kills many parasites and helps the fish breathe better. You can soak sick fish in a strong salt solution for a few minutes.
3. Antibiotics: For serious bacterial infections, you can mix special fish medicine into their feed.
4. Fresh Water: Sometimes, just draining half the pond and refilling it with fresh, clean water is all the “medicine” they need to recover.

Student Activity: The Observation Test

Go to the school pond or a nearby farm. Watch the fish for 10 minutes.

• Do you see any fish swimming upside down?
• Is there any fish “flashing” (turning sideways quickly to rub against the wall)?
• Report your findings in your notebook.

Teacher’s Closing Note: > Most fish diseases are caused by the farmer, not the fish! If you keep the water clean and don’t overfeed, your fish will stay healthy and grow big.