Grade 10 marine and fisheries technology Aquaculture – Production Systems Notes

Marine & Fisheries Technology — Aquaculture

Subtopic: Production Systems

Key Terms (simple)

Aquaculture, culture system, pond, cage, hapa, tank, raceway, recirculating aquaculture system (RAS), stocking density, aeration, feed, polyculture, monoculture, mariculture.

1. Systems of culturing fish — overview

Different systems are chosen by scale, cost, species and location. In Kenya these include:

• Earthen ponds — common in rural areas for Nile tilapia and catfish. Cheap, simple to manage.
• Cage culture — floating cages in lakes (e.g., Lake Victoria) used for tilapia and other finfish.
• Concrete/earthen tanks — used in schools, hatcheries and urban farms for tilapia and catfish.
• Hapas (net enclosures) — small nets in ponds or reservoirs for nursery stages.
• Raceways — flowing water channels for trout in cool areas or local flow-through operations.
• Recirculating aquaculture systems (RAS) — tank systems that treat and reuse water (higher tech, small footprint).
• Mariculture — sea cages or pond culture in coastal areas; also seaweed farming (Gracilaria/Eucheuma) along the Kenyan coast.
• Integrated systems — rice-fish, fish-poultry or aquaponics (plants + fish) to increase productivity and reduce waste.

2. Common species (Kenyan context)

• Nile tilapia (Oreochromis niloticus) — most common for ponds and cages.
• African catfish (Clarias gariepinus) — tolerant of low oxygen, used in tanks and ponds.
• Seaweeds (Eucheuma, Gracilaria) — coastal communities (e.g., Kilifi, Lamu) grow these for sale.
• Prawns/shrimp (in brackish systems) — limited but possible in coastal/estuarine farms.

3. Simple drawing and labelling — Example: Earthen pond production system

Below is a simple visual you can copy into your notebook. Labels point to important parts you must know.

How to draw and label (step-by-step):

1. Draw pond shape (oval or rectangle), show embankment around it.
2. Add inlet (where water enters) and outlet/drain (for harvesting and cleaning).
3. Mark aerator location, feeding area and deeper zone for fish refuge.
4. Label: inlet, outlet/drain, embankment, aerator, feeding zone, fish, vegetation (if any).
5. Write short notes about stocking density and species near the drawing (e.g., Tilapia — 2–4 fish/m² for small-scale pond).

4. Advantages and challenges of each system (simple)

• Ponds
  • Advantages: low capital, easy to manage, good for extensive/subsistence farmers.
  • Challenges: water quality changes, predators, seasonal water shortage during drought.
• Cages
  • Advantages: use open water bodies (no land cost), good growth rates.
  • Challenges: escapes, disease spread, dependence on lake conditions and regulations.
• Tanks & RAS
  • Advantages: controlled environment, high productivity, suitable near towns.
  • Challenges: high capital and energy costs, technical know-how required.
• Mariculture / Seaweed
  • Advantages: alternative income for coastal communities, low feed costs for seaweed.
  • Challenges: weather damage, market access, site selection.

5. Simple water quality basics (what 15‑year‑olds must know)

• Dissolved oxygen (DO) — fish need enough oxygen. Aeration can help.
• Temperature — affects fish growth; tilapia prefer warm water (about 24–30°C).
• pH — most culture systems need near neutral pH (6.5–8.5).
• Clarity and ammonia — cloudy water and high ammonia are signs of problems.

6. Suggested learning experiences (classroom and field)

Practical and local activities to meet the outcomes:

• Field visit: Visit a nearby fish pond, cage farm on Lake Victoria, or seaweed farm on the coast. Observe system parts and take photos/sketches.
• Drawing activity: In class, draw and label an earthen pond or a cage system. Exchange with a classmate for peer marking against a checklist (inlet, outlet, aerator, embankment, feeding area).
• Group project: Design a small homestead system for a household (choose pond, tank or hapa) with notes on species, stocking density, feed plan and cost estimate.
• Simple experiment: Measure temperature and turbidity (with a Secchi disk or simple turbidity tube) of pond or lake water and discuss suitability for fish.
• Role-play / debate: Split class: one side argues for ponds, the other for cages — consider costs, environment and market access.
• Local examples research: Collect stories from local farmers (tilapia, catfish, seaweed) and present how the production system helps their family income.
• Safety and environment lesson: Discuss safe use of chemicals (avoid chemicals that kill fish), proper disposal of waste, and preventing escapes into natural waters.

Assessment ideas

• Short quiz: name 4 systems, list one advantage and one challenge for each.
• Practical test: draw and label a pond system (show inlet, outlet, aerator, feeding zone).
• Project mark: group design and presentation of a small farm plan with budget and species choice.

Teacher notes (quick tips)

• Link lessons to local farms — many Kenyan regions have excellent small-scale examples.
• Emphasize sustainability: good records, water management, and preventing disease.
• Encourage simple record keeping for students (date, stocking, feed given, mortalities).