Fishing and Fish Farming in Rwanda

Lessons

Senior 2 · Geography and Environment

Fishing and Fish Farming in Rwanda

3 lessons

Lesson 2 of 3

Factors and methods of fishing

22 min

Why this matters

Why do fishers on Lake Kivu work at night while pond farmers in the valleys work by day? The method used depends on the fish, the water and the market. Choosing the right method decides how much is caught, and whether young fish survive to keep the stock going. This lesson explains what favours fishing in Rwanda and how fish are caught and farmed.

Factors that favour fishing and fish farming

Physical factors	Human and economic factors
Many lakes, rivers and swamps, with Lake Kivu the largest Plankton and water plants that fish feed on Warm water, in which tilapia grow quickly Valleys with a steady flow of water to fill ponds	A large, growing market: a dense population, towns such as Kigali, Musanze and Rubavu, and buyers across the border in Goma and Bukavu Cheap local materials for boats, poles and baskets Cooperatives that share boats, nets and cold storage Government support: fingerlings, training, feed and lake patrols Better roads that carry fresh fish to towns quickly

Methods of fishing

Method	How it works	Used for
Lamp and lift-net fishing	Crews in three boats joined by long poles go out at night and hang lamps over the water. The light draws the shoals up; a large net hung between the boats is then lifted.	Isambaza on Lake Kivu
Gill net	A wall of net is left standing in the water. Fish swim into it and are held by their gills. The mesh size decides the size of fish caught.	Tilapia and other medium-sized fish in most lakes
Seine net	A long net is drawn in a curve around a shoal and pulled in to the shore or a boat.	Shallow shores; it scoops up young fish and damages breeding areas, so it is tightly controlled
Hook and line	Baited hooks on a line from a canoe or the bank; one fish at a time	Individual fishers; catfish and tilapia
Basket and fence traps	Woven baskets or reed fences set in shallow water; fish swim in but cannot find the way out	Swamps and river mouths; catfish

Methods of fish farming

Earth ponds: the farmer fills the pond, adds manure so that plankton grows, stocks fingerlings, feeds them, and harvests by draining the pond, often after about six months.
Floating cages: a net enclosure anchored in a lake, with fish fed on pellets. Many fish fit in a small space, but uneaten feed and droppings can pollute the water, and disease spreads quickly.

Worked example: planning a pond harvest (illustrative figures)

A cooperative in Gisagara stocks a 400 m² pond at 3 fingerlings per m². 80% survive, and each fish reaches 250 g. The fish sell at 2,500 Frw per kg. Find the harvest and its value.

Fingerlings stocked = 400 × 3 = 1,200.
Fish harvested = 80% of 1,200 = 0.8 × 1,200 = 960.
Mass harvested = 960 × 0.25 kg = 240 kg (change grams to kilograms first: 250 g = 0.25 kg).
Value = 240 × 2,500 = 600,000 Frw, before the cost of feed and fingerlings is taken away.

Tip

Exam technique. For "methods of fishing", give the name, how it works and where it is used. "Gill net: fish are held by their gills in a standing wall of net; used for tilapia on Lake Muhazi" earns full marks, while "gill net" alone does not.

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Practice

1

Why do isambaza fishers use lamps?

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Solution: the shoals rise towards the light at night and gather under the boats, so the lift net comes up full.

2

How does a larger mesh size help to conserve fish?

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Solution: young, small fish slip through the mesh, grow up and breed, so the stock is renewed.

3

State two human factors that favour fishing on Lake Kivu.

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Solution: a ready market in Rubavu, Karongi and Goma, and cooperatives that share boats and nets (also roads, cheap local materials).

4

A 250 m² pond is stocked at 4 fingerlings per m². 75% survive and each reaches 300 g. Find the mass harvested.

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Solution: stocked = 250 × 4 = 1,000; harvested = 0.75 × 1,000 = 750 fish; mass = 750 × 0.3 kg = 225 kg.

5

Give one advantage and one disadvantage of cage farming.

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Solution: advantage: many fish in a small space on an existing lake. Disadvantage: uneaten feed and droppings pollute the water, and disease spreads fast.

Summary

Fishing is favoured by many lakes, plankton and warm water, and by a large market, cooperatives, roads and government support.
Methods: lamp and lift nets (isambaza), gill nets, seine nets, hook and line, and traps.
Fish farming uses earth ponds and floating cages. Stocked × survival × mass per fish gives the harvest.

Sources and credits

Kapenta (Tanganyika sardine fishing): Wikipedia contributors, Wikipedia, CC BY-SA 4.0, adapted by Ganzaa.
Lake Kivu: Wikipedia contributors, Wikipedia, CC BY-SA 4.0, adapted by Ganzaa.
Fisher men in Lake Kivu, Rwanda: photo by Isma250, Wikimedia Commons, CC BY-SA 4.0.

The factor and method tables, the worked example (illustrative figures) and the practice items are written by Ganzaa.

This lesson adapts CC BY-SA material and is shared under CC BY-SA 4.0.

1Why this matters

2Factors that favour fishing and fish farming

3Methods of fishing

4Methods of fish farming

Worked example: planning a pond harvest (illustrative figures)

Practice

Why this matters

Factors that favour fishing and fish farming

Methods of fishing

Methods of fish farming