Fish Harvesting – SS2 Livestock Farming Lesson Note (First Term)

Fish harvesting is the process of removing fish from the pond once they have reached table size, the size the market wants. It can be partial, where only the big fish are caught, or total, where the pond is emptied at the end of the production cycle. Harvested fish are then processed to prevent spoilage.

Behavioural objectives

By the end of the lesson, students should be able to:

• define fish harvesting and state the two ways of harvesting fish;
• state the best time of day to harvest fish and give the reason;
• describe the methods and tools used for harvesting fish;
• give reasons why fish is processed;
• describe smoking, salting, sun-drying and freezing;
• list the steps in fish processing.

What is fish harvesting?

Harvesting is the “payday” for every fish farmer. It is the process of removing fish from the pond once they have reached the size the market wants (usually called table size).

In Nigeria, harvesting can be done in two ways:

1. Partial harvesting: You only catch the big fish and leave the small ones to keep growing. You use a net with large holes so the “babies” can swim through.
2. Total harvesting: You empty the entire pond and catch every single fish. This usually happens at the end of the production cycle (after 4 to 6 months).

What is the best time to harvest?

Always harvest in the cool of the morning (before 9:00 am) or in the late evening. If you harvest under the hot sun, the fish will get stressed, die quickly, and start to spoil before they even get to the market.

What are the methods of harvesting fish?

Depending on the type of pond you have, you will need different tools to get the fish out:

• Impounding (draining): If you have a “monk” or a drain pipe, you simply let the water out. As the water level drops, the fish gather in one small area, making them easy to scoop up with baskets or hand nets.
• Seine netting: This is a long net with weights at the bottom and floats at the top. Two or more people pull it across the pond to “sweep” the fish to one side.
• Cast nets: This is a circular net thrown by one person. It is good for partial harvesting when you just want a few fish for dinner or a specific customer.
• Hook and line: This is not very common on big farms, but it is used in very large earthen ponds or dams.

Why do we process fish?

The moment a fish dies, it starts to go bad (rot). In our warm Nigerian weather, a fresh fish can spoil in less than 6 hours.

We process fish to:

1. Prevent spoilage: To stop bacteria from eating the meat.
2. Add value: Smoked fish often sells for more money than fresh fish.
3. Make transport easy: Dried fish is lighter and does not need a refrigerator, so you can send it to far cities like Kano or Lagos.
4. Change the taste: Many people prefer the “woody” smoky flavour of dried catfish in their soup.

How is fish processed?

Here are the common ways of keeping fish “good” for a long time.

Smoking (the most popular way)

Fish are cleaned and placed in a smoking kiln or over a charcoal fire. The heat dries out the water, and the smoke kills bacteria.

• Pro tip: Use hardwoods for smoking. Avoid plastic or painted wood, as the fumes are poisonous.

Salting

Dry salt is rubbed into the fish. Salt draws out the moisture that bacteria need to grow. This is often combined with sun-drying.

Sun-drying

The fish are spread on mats or hung on wires under the hot sun. This is very cheap, but it depends on the weather and can be unhygienic because of flies.

Freezing

If you have electricity and a deep freezer, you can keep fish fresh for months. This is best for large cold rooms and supermarkets.

What are the steps in fish processing?

Before you smoke or dry your fish, you must follow these steps to make sure it is safe to eat:

1. Degutting: Removing the intestines and internal organs. If you leave these, the fish will taste bitter and spoil faster.
2. Scaling/cleaning: Removing scales (for tilapia) or the “slime” (for catfish). Many farmers use salt or alum to wash off the slippery slime on catfish.
3. Washing: Use clean, drinkable water to rinse the fish thoroughly.
4. Folding/brining: Some people fold the catfish into a “circle” (using a small stick) to make it look attractive before smoking.
5. Packaging: Once dried, pack the fish in clean cartons or nylon bags to keep out dust and insects.

Student discussion and practical work

• The smell test: If you go to the market, how can you tell a fresh fish from a spoiled one? (Hint: Look at the gills. They should be bright red, not brown.)
• The cost maths: If 1kg of fresh fish sells for ₦2,000 and 1kg of smoked fish (which takes 3kg of fresh fish to make) sells for ₦7,000, which one is more profitable?

Note to students: Harvesting is physically hard work. Always wear boots and be careful of the “stings” or “spines” on the side of the catfish’s head. They can be very painful.

Evaluation

1. What is fish harvesting?
2. Explain the difference between partial harvesting and total harvesting.
3. Why should fish be harvested in the cool of the morning or late evening?
4. Give four reasons why fish is processed.
5. Describe how fish is smoked.

Assignment

List the steps in fish processing in the order given in the lesson. Explain why degutting is necessary.