Fish Farming Practice Booklet - Questions &
Worked Solutions
Each problem states the question first, followed by a step-by-step solution. Use for practice and
revision.
Problem 1
Question:
A farmer builds a pond of 120 m². He will stock at 6 fingerlings/m². Each fingerling weighs 0.3 g and
is fed at 5% BW/day. At harvest each fish weighs 500 g and is fed at 1.2% BW/day. Total cost =
GH¢ 1,000. Desired profit = 20%.
Questions:
1. How many fingerlings are stocked?
2. How much feed is given daily at the fingerling stage?
3. How much feed is given daily at adult stage?
4. What is the selling price per fish for the desired profit?
Solution:
1) Number stocked = 120 × 6 = 720 fingerlings.
2) Fingerling biomass = 720 × 0.3 g = 216 g.
Daily feed = 5% × 216 g = 0.05 × 216 = 10.8 g/day.
3) Adult biomass = 720 × 500 g = 360,000 g = 360 kg.
Daily feed = 1.2% × 360 kg = 0.012 × 360 = 4.32 kg/day.
4) Required revenue = 1,000 × (1 + 0.20) = 1,200 GH¢.
Price per fish = 1,200 ÷ 720 = 1.666... ≈ GH¢ 1.67 per fish.
Problem 2
Question:
A 80 m² pond is stocked at 8 fingerlings/m². Fingerling wt = 0.2 g fed at 5% BW/day. Adult wt = 600
g fed at 1.2% BW/day. Cost = GH¢ 900. Desired profit = 10%.
Questions:
1. Number stocked?
2. Daily feed for fingerlings?
3. Daily feed for adults?
4. Selling price per fish?
Solution:
1) Number = 80 × 8 = 640 fingerlings.
2) Biomass = 640 × 0.2 g = 128 g. Daily feed = 0.05 × 128 = 6.4 g/day.
3) Adult biomass = 640 × 600 g = 384,000 g = 384 kg. Daily feed = 0.012 × 384 = 4.608 kg/day.
4) Revenue = 900 × 1.10 = 990 GH¢. Price = 990 ÷ 640 = 1.546875 ≈ GH¢ 1.55 per fish.
, Problem 3
Question:
Pond area = 50 m²; stocking = 10/m²; fingerling wt = 0.1 g fed at 5% BW/day; adult wt = 200 g fed at
2% BW/day. Cost = GH¢ 300. Profit = 15%.
Questions:
1. Number stocked?
2. Fingerling daily feed?
3. Adult daily feed?
4. Price per fish?
Solution:
1) Number = 50 × 10 = 500 fish.
2) Biomass = 500 × 0.1 g = 50 g. Daily feed = 0.05 × 50 = 2.5 g/day.
3) Adult biomass = 500 × 200 g = 100,000 g = 100 kg. Daily feed = 0.02 × 100 = 2.0 kg/day.
4) Revenue = 300 × 1.15 = 345 GH¢. Price = 345 ÷ 500 = 0.69 GH¢ per fish.
Problem 4
Question:
Pond = 300 m²; stocking = 5/m²; fingerling wt = 1 g fed at 5% BW/day; adult wt = 1200 g fed at 1.2%
BW/day. Cost = GH¢ 6,500. Profit = 40%.
Questions:
1. Number stocked?
2. Fingerling feed/day?
3. Adult feed/day?
4. Selling price per fish?
Solution:
1) Number = 300 × 5 = 1,500 fish.
2) Biomass = 1,500 × 1 g = 1,500 g. Daily feed = 0.05 × 1,500 = 75 g/day.
3) Adult biomass = 1,500 × 1,200 g = 1,800,000 g = 1,800 kg. Daily feed = 0.012 × 1,800 = 21.6
kg/day.
4) Revenue = 6,500 × 1.40 = 9,100 GH¢. Price = 9,100 ÷ 1,500 = 6.066... ≈ GH¢ 6.07 per fish.
Problem 5
Question:
Pond = 150 m²; stocking = 5/m²; fingerling wt = 0.5 g fed at 5% BW/day; adult wt = 920 g fed at
1.2% BW/day. Cost = GH¢ 3,900. Profit = 25%.
Questions:
1. Number stocked?
2. Fingerling feed/day?
3. Adult feed/day?
4. Price per fish?
Worked Solutions
Each problem states the question first, followed by a step-by-step solution. Use for practice and
revision.
Problem 1
Question:
A farmer builds a pond of 120 m². He will stock at 6 fingerlings/m². Each fingerling weighs 0.3 g and
is fed at 5% BW/day. At harvest each fish weighs 500 g and is fed at 1.2% BW/day. Total cost =
GH¢ 1,000. Desired profit = 20%.
Questions:
1. How many fingerlings are stocked?
2. How much feed is given daily at the fingerling stage?
3. How much feed is given daily at adult stage?
4. What is the selling price per fish for the desired profit?
Solution:
1) Number stocked = 120 × 6 = 720 fingerlings.
2) Fingerling biomass = 720 × 0.3 g = 216 g.
Daily feed = 5% × 216 g = 0.05 × 216 = 10.8 g/day.
3) Adult biomass = 720 × 500 g = 360,000 g = 360 kg.
Daily feed = 1.2% × 360 kg = 0.012 × 360 = 4.32 kg/day.
4) Required revenue = 1,000 × (1 + 0.20) = 1,200 GH¢.
Price per fish = 1,200 ÷ 720 = 1.666... ≈ GH¢ 1.67 per fish.
Problem 2
Question:
A 80 m² pond is stocked at 8 fingerlings/m². Fingerling wt = 0.2 g fed at 5% BW/day. Adult wt = 600
g fed at 1.2% BW/day. Cost = GH¢ 900. Desired profit = 10%.
Questions:
1. Number stocked?
2. Daily feed for fingerlings?
3. Daily feed for adults?
4. Selling price per fish?
Solution:
1) Number = 80 × 8 = 640 fingerlings.
2) Biomass = 640 × 0.2 g = 128 g. Daily feed = 0.05 × 128 = 6.4 g/day.
3) Adult biomass = 640 × 600 g = 384,000 g = 384 kg. Daily feed = 0.012 × 384 = 4.608 kg/day.
4) Revenue = 900 × 1.10 = 990 GH¢. Price = 990 ÷ 640 = 1.546875 ≈ GH¢ 1.55 per fish.
, Problem 3
Question:
Pond area = 50 m²; stocking = 10/m²; fingerling wt = 0.1 g fed at 5% BW/day; adult wt = 200 g fed at
2% BW/day. Cost = GH¢ 300. Profit = 15%.
Questions:
1. Number stocked?
2. Fingerling daily feed?
3. Adult daily feed?
4. Price per fish?
Solution:
1) Number = 50 × 10 = 500 fish.
2) Biomass = 500 × 0.1 g = 50 g. Daily feed = 0.05 × 50 = 2.5 g/day.
3) Adult biomass = 500 × 200 g = 100,000 g = 100 kg. Daily feed = 0.02 × 100 = 2.0 kg/day.
4) Revenue = 300 × 1.15 = 345 GH¢. Price = 345 ÷ 500 = 0.69 GH¢ per fish.
Problem 4
Question:
Pond = 300 m²; stocking = 5/m²; fingerling wt = 1 g fed at 5% BW/day; adult wt = 1200 g fed at 1.2%
BW/day. Cost = GH¢ 6,500. Profit = 40%.
Questions:
1. Number stocked?
2. Fingerling feed/day?
3. Adult feed/day?
4. Selling price per fish?
Solution:
1) Number = 300 × 5 = 1,500 fish.
2) Biomass = 1,500 × 1 g = 1,500 g. Daily feed = 0.05 × 1,500 = 75 g/day.
3) Adult biomass = 1,500 × 1,200 g = 1,800,000 g = 1,800 kg. Daily feed = 0.012 × 1,800 = 21.6
kg/day.
4) Revenue = 6,500 × 1.40 = 9,100 GH¢. Price = 9,100 ÷ 1,500 = 6.066... ≈ GH¢ 6.07 per fish.
Problem 5
Question:
Pond = 150 m²; stocking = 5/m²; fingerling wt = 0.5 g fed at 5% BW/day; adult wt = 920 g fed at
1.2% BW/day. Cost = GH¢ 3,900. Profit = 25%.
Questions:
1. Number stocked?
2. Fingerling feed/day?
3. Adult feed/day?
4. Price per fish?
