TLE 8 AFA W4D5: Exploring aquaculture methods for sustainable fish farming (Part 2)

🎯 Learning Goals – Day 5

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

1. Trace the history and development of fishpond, cage, and pen aquaculture systems.
2. Identify the different aquaculture practices such as raft, pole, longline, metaline, monoculture, polyculture, and integrated systems.
3. Explain the advantages and limitations of fishpond, cage, and pen culture systems.
4. Analyze the environmental and site requirements (soil, tidal range, water quality, depth, and area) for aquaculture facilities.
5. Evaluate the role of brackishwater, freshwater, marine, and open-water systems in sustainable aquaculture.

🧩 Key Ideas & Terms – Day 5

• Fishpond Aquaculture – Oldest form of aquaculture; raising fish in man-made or natural ponds.
• Cage Culture – Raising fish inside framed enclosures placed in rivers, lakes, or seas.
• Pen Culture – Larger enclosures fixed to the natural bottom of lakes, rivers, or coastal areas.
• History of Aquaculture Systems – Fishponds (China, 1400–1137 B.C.), Cages (Kampuchia, ~200 years ago), Pens (Japan 1920s → China 1950s → Philippines 1968).
• Species in Fishponds – Tilapia, catfish, carp, eels, trout, shrimp, milkfish, mullet, grouper, prawns.
• Species in Cages – Milkfish, tilapia, carp, grouper, siganid.
• Species in Pens – Milkfish, carp, tilapia, mullet.
• Cage Components – Frame, floats, sinkers, nets (inner, outer, cover).
• Cage Types – Fixed, floating, submerged, movable.
• Advantages of Cage Culture – Low investment, optimum feed use, easy management, fast growth.
• Limitations of Cage Culture – Theft, disease outbreaks, water quality dependence, fouling, environmental impact.
• Pen Culture Barriers – Nets, bamboo scaffolds, wire mesh, nylon screens.
• Types of Enclosures in Pen Culture – Bamboo scaffolding pens, floating net pens, single-layer nylon pens.
• Merits of Pen Culture – Assured production, continuous water exchange, simple technology, employment.
• Demerits of Pen Culture – Predator damage, weeds, biofouling, red tide, storm/weather damage.
• Raft Culture – Floating rafts used to grow shellfish like mussels and oysters.
• Pole Culture (Bouchot) – Shellfish attached to poles/stakes in intertidal zones.
• Longline Culture – Ropes suspended horizontally in water for mussels and seaweed.
• Metaline Culture – Mollusk culture using stakes or lines in shallow waters.
• Open-Water Systems – Using lakes, rivers, and seas directly for aquaculture (pens, cages, rafts, etc.).
• Brackishwater Culture – Farming in partly salty, partly fresh environments (estuaries, mangroves).
• Freshwater Culture – Farming in rivers, lakes, and ponds (tilapia, carp).
• Marine/Mariculture – Farming in seawater (seaweed, oysters, mussels, grouper).
• Tidal Ponds – Aquaculture ponds designed to use tidal exchange for water renewal.
• Soil Requirement – Clay-loam soil to hold water in ponds.
• Tidal Range Requirement – At least 2–3 meters for effective pond exchange.
• Water Quality – pH between 6.5–9; good dissolved oxygen.
• Pond Proportions – Nursery ponds (1–4%), transition ponds (6–9%), rearing ponds (majority).
• Pen Dimensions – Depth of 3–5 meters; typical area 2–7 hectares.
• Integrated Aquaculture – Combining aquaculture with agriculture (e.g., livestock manure as fertilizer).
• Monoculture – Farming one species only.
• Polyculture – Farming multiple species together to maximize resources.

🔄 Quick Recall / Prior Knowledge – Day 5

Quick Recall (Multiple Choice)

Directions: Choose the correct answer.

1. Which country is credited with the earliest fishpond aquaculture during the Yin Dynasty (1400–1137 B.C.)?
   a) Japan
   b) China
   c) Philippines
   d) Kampuchia
2. Cage culture originated in which country about 200 years ago?
   a) Kampuchia
   b) Japan
   c) China
   d) India
3. Which aquaculture system uses large enclosures fixed to the bottom of lakes or bays?
   a) Cage culture
   b) Pen culture
   c) Pond culture
   d) Raft culture
4. Which aquaculture practice grows mussels on floating rafts?
   a) Longline culture
   b) Pole culture
   c) Raft culture
   d) Pen culture
5. What is the ideal soil type for constructing fishponds?
   a) Sandy soil
   b) Clay-loam soil
   c) Rocky soil
   d) Silty soil

Show Answer

1. b) China
2. a) Kampuchia
3. b) Pen culture
4. c) Raft culture
5. b) Clay-loam soil

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Prior Knowledge (Short Answer)

Answer briefly in your notebook.

1. Have you seen a fishpond, cage, or pen culture system in your community? Which one?
2. What are some common fish or shellfish farmed in your area?
3. Why do you think farmers choose brackish, freshwater, or marine environments for aquaculture?
4. How do tides affect fishpond and pen operations?
5. Why might some farmers prefer monoculture while others choose polyculture?

Show Answer

1. (Answers will vary – many rural areas have tilapia ponds, milkfish cages, or mussel rafts.)
2. (Tilapia, carp, bangus, shrimp, oysters, mussels, seaweed depending on region.)
3. Farmers match species to their natural habitats – e.g., shrimp in brackish, tilapia in freshwater.
4. Tides help with natural water exchange for ponds and pens.
5. Monoculture is simpler, but polyculture makes better use of resources and reduces waste.

📖 Explore the Lesson – Day 5

Introduction: Why Study Aquaculture Systems?

Aquaculture is the science and practice of raising aquatic organisms like fish, shellfish, and seaweeds in controlled environments. It provides food, jobs, and income for millions of families worldwide. In the Philippines, aquaculture supports food security and exports, especially with species like tilapia, milkfish (bangus), shrimp, mussels, and oysters.

To understand aquaculture well, we need to study not only the common systems like ponds and cages, but also special practices like raft, pole, longline, and pen culture. Each method has its own history, site requirements, species, advantages, and limitations. Knowing these helps future aquaculture technicians choose the right method for sustainable production.

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1. History of Aquaculture Systems

Aquaculture is not new—it has been practiced for thousands of years.

• Fishpond Culture: This is considered the oldest form of aquaculture. Records show that the Chinese practiced pond aquaculture as early as the Yin Dynasty (1400–1137 B.C.), raising carps in freshwater ponds. From there, fishpond aquaculture spread across Asia and the world.
• Cage Culture: This method originated in Kampuchia about 200 years ago. At first, cages were used only to transport fish. Later, people discovered that fish could be grown inside cages for long-term culture, which made this system popular in rivers, lakes, and coastal seas.
• Pen Culture: Pen aquaculture began in Japan in the 1920s, reached China in the 1950s, and was introduced to the Philippines between 1968 and 1970 in Laguna de Bay and San Pablo lakes through the work of BFAR and LLDA. Pens became important for milkfish culture but also faced challenges like predators, fouling, and water pollution.

By studying these beginnings, we can see how people used local environments and technology to improve food production from water.

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2. Fishpond Culture System

a) What is a Fishpond?

A fishpond is an enclosed body of water where fish are raised. Ponds may be natural or man-made, and they can be filled by rain, rivers, or tidal water. Fishponds can be found in freshwater, brackishwater, or even marine areas.

b) Species Raised in Fishponds

• Freshwater ponds: tilapia, catfish, carp, eels, trout.
• Brackishwater ponds: milkfish, shrimps, mullets.
• Marine ponds: groupers, sea bass, marine prawns.

c) Site Selection for Fishponds

Choosing a good site is crucial. A poor site will lead to poor production even with good management. Important factors include:

• Soil: should be clay-loam to hold water and slightly alkaline for good productivity.
• Elevation and Tidal Range: tidal ponds should have 2–3 m tidal range for proper water exchange.
• Vegetation: presence of mangroves or nipa palms indicates suitable brackishwater soil.
• Water Quality: water should have a pH of 6.5–9 and good dissolved oxygen.
• Accessibility: sites must be near roads and markets, with available labor.

d) Pond Layout

A good pond layout ensures efficiency in feeding, harvesting, and water management.

• Nursery ponds: 1–4% of the total area.
• Transition ponds: 6–9% of the total area.
• Rearing ponds: majority of the area.
• Water supply and drainage canals: must be well-designed for easy filling and draining.

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3. Cage Culture System

a) What is Cage Culture?

Cage culture is a method where fish are raised inside framed enclosures made of nets, placed in rivers, lakes, reservoirs, or coastal waters. The natural water provides oxygen and removes waste, while the net keeps the fish confined.

b) Components of a Fish Cage

• Frame – provides the shape and support.
• Floats – keep the cage floating.
• Sinkers – keep the net stretched down.
• Nets – inner, outer, and cover nets to prevent fish escape and protect against predators.

c) Types of Cages

• Fixed cages – attached to poles or structures.
• Floating cages – supported by bamboo or drums.
• Submerged cages – anchored under water.
• Movable cages – can be transferred from one site to another.

d) Species Raised in Cages

Milkfish, tilapia, carps, groupers, siganids, and other high-value fish.

e) Advantages of Cage Culture

• Low investment and simple construction.
• Easy feeding and harvesting.
• Uses existing water bodies.
• Faster growth due to high stocking density.
• Feeds are efficiently used.

f) Limitations of Cage Culture

• Susceptible to theft and vandalism.
• High risk of disease outbreaks.
• Strongly dependent on water quality.
• Fouling of nets by algae and dirt.
• Feed loss if not properly managed.
• May cause environmental pollution if overstocked.

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4. Pen Culture System

a) What is a Fish Pen?

Pen culture involves building larger enclosures than cages, with barriers fixed to the natural bottom of lakes, rivers, or coastal bays. Pens allow fish to grow in a more natural environment but still under controlled conditions.

b) History

• Started in Japan (1920s).
• Spread to China (1950s).
• Introduced to the Philippines in 1968–1970 at Laguna de Bay and San Pablo lakes.

c) Site Requirements

• Shallow waters (<10 m).
• Depth of 3–5 m.
• Typical area of 2–7 hectares.
• Substrate and water flow must support the species to be cultured.

d) Barriers and Enclosures Used in Pens

• Bamboo scaffolding.
• Floating nets supported by frames.
• Single-layer nylon or wire mesh fixed with posts.
• Additional support (buttresses) for areas exposed to strong winds or waves.

e) Species Raised in Pens

Milkfish, carp, tilapia, mullet.

f) Merits of Pen Culture

• Assured production and higher yield.
• Continuous water exchange and flushing of wastes.
• Simple technology and lower capital cost compared to full ponds.
• Provides employment opportunities.

g) Demerits of Pen Culture

• Damage by predators like crabs and birds.
• Weed growth and hydrogen sulfide buildup.
• Biofouling of nets and structures.
• Susceptible to red tide and climate changes.
• Some species not suitable.
• Can be damaged by strong winds or typhoons.

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5. Other Aquaculture Practices

Besides ponds, cages, and pens, other special practices:

• Raft Culture – mussels or oysters grown on floating wooden rafts.
• Pole Culture (Bouchot) – shellfish grown on poles or stakes in intertidal zones.
• Longline Culture – ropes stretched horizontally in water, used for seaweed and mussels.
• Metaline Culture – mollusks attached to lines or stakes in shallow waters.
• Open-Water Systems – direct use of lakes, rivers, seas for aquaculture.
• Integrated Aquaculture – combining fish farming with agriculture or livestock (e.g., using animal manure to fertilize ponds).
• Monoculture – one species only; simpler but riskier.
• Polyculture – multiple species in one system; sustainable and efficient.

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6. Environmental Requirements in Aquaculture

• Brackishwater culture: estuaries and mangroves with mixed salinity.
• Freshwater culture: rivers, lakes, and ponds.
• Marine/Mariculture: seawater environments for seaweed, shellfish, and marine fish.
• Tidal influence: essential for pond and pen systems for water exchange.
• Soil quality: clay-loam for pond dikes and bottoms.
• Water quality: pH between 6.5–9, dissolved oxygen for healthy fish.

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7. Area & Depth Requirements

• Nursery ponds: 1–4% of the farm area.
• Transition ponds: 6–9%.
• Rearing ponds: majority of the area.
• Pen culture: 3–5 m deep; 2–7 hectares typical size.

These specifications ensure that fish are properly distributed, water quality is maintained, and the environment is not overloaded beyond its carrying capacity.

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Key Message

Aquaculture systems vary widely—from ancient fishponds to modern cages and pens, to specialized raft, pole, longline, and metaline methods. Each has its advantages and limitations. The environment—soil, water quality, tidal range—must always be considered. By following proper area and depth requirements, and matching the right method to the right site, aquaculture can provide food and income while protecting the environment.

💡 Example in Action – Day 5

Worked Example: Choosing Between Cage and Pen Culture

Mario is a young farmer living near a large freshwater lake. He wants to raise tilapia to support his family’s income. He has two choices: cage culture or pen culture.

• Option A – Cage Culture
  Requires a smaller investment.
  Easy to set up and manage.
  Can be moved if water conditions worsen.
  Risk: cages are vulnerable to theft and net fouling.
• Option B – Pen Culture
  Requires larger area (2–7 hectares).
  Offers continuous water exchange and natural feeding.
  Higher yield than cages.
  Risk: pens may be damaged by storms, predators, or red tide.

Decision:
Mario chooses cage culture because he has limited funds and wants to start small. He also plans to use floating cages, which are cheaper and movable. Later, if he gains more income, he may expand to pen culture.

Lesson from Mario’s Example:
The choice of aquaculture system depends on resources, site conditions, and long-term goals. Starting small with cages is safer for beginners, while pens may be more profitable for larger-scale farmers.

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Now You Try!

Ana owns land near the coast. She wants to raise milkfish. She is considering fishpond culture or pen culture.

Questions:

1. What are the advantages of fishpond culture for Ana?
2. What are the disadvantages of pen culture for her?
3. If Ana values sustainability, which system would you recommend and why?

Show Answer

1. Advantages of fishpond culture: Easy to manage, uses natural pond food, protected from strong waves, lower risk of pollution.
2. Disadvantages of pen culture: Expensive setup, vulnerable to storms and predators, risk of red tide.
3. Recommended: Fishpond culture – it is more manageable, sustainable, and suited for small to medium-scale farmers like Ana.

📝 Try It Out – Day 5

Practice 1 – Multiple Choice

Choose the correct answer.

1. Which aquaculture system originated in Kampuchia about 200 years ago?
   a) Pen culture
   b) Fishpond culture
   c) Cage culture
   d) Raft culture
2. Which species is commonly raised in brackishwater ponds?
   a) Tilapia
   b) Shrimp
   c) Trout
   d) Carp
3. What is the recommended soil type for constructing fishponds?
   a) Sandy
   b) Clay-loam
   c) Rocky
   d) Silty
4. Which culture practice involves attaching shellfish to poles in intertidal zones?
   a) Raft culture
   b) Pole culture
   c) Longline culture
   d) Metaline culture
5. What is the typical depth of a fish pen?
   a) 1–2 meters
   b) 3–5 meters
   c) 6–8 meters
   d) Over 10 meters

Show Answer

1. c) Cage culture
2. b) Shrimp
3. b) Clay-loam
4. b) Pole culture
5. b) 3–5 meters

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Practice 2 – True or False

Write T if the statement is true, F if false.

1. Fishpond aquaculture began in the Philippines during the 1900s.
2. Pen culture enclosures are fixed to the natural bottom of a lake or bay.
3. Cage culture is less expensive than pen culture and can be moved if needed.
4. Raft culture is mainly used for oysters and mussels.
5. Red tide is a common problem in pen culture.

Show Answer

1. F (It started in China during the Yin Dynasty, 1400–1137 B.C.)
2. T
3. T
4. T
5. T

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Practice 3 – Short Response / Analysis

Answer briefly in your notebook.

1. Why is tidal range important in brackishwater fishponds?
2. Give one advantage and one limitation of cage culture.
3. What is the function of sinkers in a fish cage?
4. Why is clay-loam soil better for pond construction than sandy soil?
5. If you were to start an aquaculture business, which system would you choose (pond, cage, pen, raft, pole, or longline) and why?

Show Answer

1. Tides allow natural water exchange in ponds.
2. Advantage: low cost; Limitation: vulnerable to theft and fouling.
3. Sinkers keep the net stretched down and stable.
4. Clay-loam holds water better and prevents leakage.
5. Answers will vary (students justify their choice).

✅ Check Yourself – Mixed Quiz (10 Items)

Part A – Multiple Choice (1–4)

1. Which aquaculture system was introduced in the Philippines around 1968–1970 in Laguna de Bay?
   a) Cage culture
   b) Pen culture
   c) Raft culture
   d) Fishpond culture
2. Which of the following is a merit of pen culture?
   a) High cost of construction
   b) Continuous water exchange
   c) Prone to predators
   d) Easily damaged by storms
3. Which species is commonly raised in marine aquaculture?
   a) Tilapia
   b) Milkfish
   c) Carp
   d) Seaweed
4. Which component of a fish cage keeps it afloat?
   a) Sinkers
   b) Nets
   c) Floats
   d) Frames

Part B – True or False (5–7)

5. Cage culture requires enclosures fixed to the bottom of a water body.
6. Red tide can cause mass mortality in pen aquaculture.
7. Pond nursery areas usually make up 10–20% of the total farm area.

Part C – Short Answer (8–10)

8. State one advantage and one limitation of raft culture.
9. Why is clay-loam soil important in pond aquaculture?
10. Explain why stocking density and water quality are critical in cage culture.

Show Answer Key

Part A – Multiple Choice

1. b) Pen culture
2. b) Continuous water exchange
3. d) Seaweed
4. c) Floats

Part B – True or False

5. False (That’s pen culture; cages float in open water)
6. True
7. False (Nursery ponds are 1–4% only)

Part C – Short Answer

8. Advantage: simple, low-cost; Limitation: weather and wave damage, limited to certain species.
9. Clay-loam holds water well and prevents seepage, making ponds effective.
10. Overstocking reduces oxygen and increases waste; clean water ensures healthy, fast-growing fish.

🚀 Go Further – Day 5

Activity 1 – Aquaculture System Poster

Task: Create a poster comparing fishpond, cage, and pen culture systems.

• Show their history, advantages, limitations, and species raised.
• Use drawings, diagrams, or printed pictures.

Sample Output

A poster with three sections:
- Fishponds – oldest method, tilapia/carp, requires clay-loam soil.
- Cages – movable, low cost, tilapia/milkfish, but prone to theft.
- Pens – large, continuous water flow, milkfish/carp, but affected by storms.

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Activity 2 – Debate: Cage vs. Pen Culture

Task: Form two groups.

• Group A argues that cage culture is better for small-scale farmers.
• Group B argues that pen culture is better for large-scale sustainable aquaculture.
• Each group must present at least 2 arguments and 1 counter-argument.

Sample Output

- Group A: Lower cost, movable, easy to manage.
- Group B: Higher yield, continuous water exchange, more jobs.

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Activity 3 – Site Selection Checklist

Task: Visit a nearby water body (pond, river, lake, or coastal area). In your notebook, write down observations using this checklist:

• Soil type
• Tidal influence / water flow
• Vegetation (mangroves, nipa, etc.)
• Water pH or clarity (if test kit available)
• Accessibility (roads, market, manpower)

Sample Output

- Soil: clay-loam, good for pond dikes
- Tidal influence: moderate, good exchange
- Vegetation: nipa present → brackishwater suitability
- pH: ~7.2, within range
- Accessibility: near farm-to-market road

🔗 My Reflection – Day 5

Option 1 – 3–5 Sentences Reflection

In your notebook, write 3–5 sentences about what you learned today.

• Mention which aquaculture system (pond, cage, pen, raft, pole, longline, or metaline) you find most interesting.
• Explain why you think it is important for sustainable aquaculture.
• Share one challenge that farmers might face with this system.

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Option 2 – Guiding Questions

Answer the following in your notebook:

1. Which aquaculture system (fishpond, cage, or pen) do you think is most suitable for your community? Why?
2. How do environmental factors like tides, soil, and water quality affect aquaculture success?
3. What lesson from today’s discussion can be applied to make aquaculture more sustainable in the Philippines?

🎣 Take the Aquaculture & Fish Capture Quiz