Aquaculture
Big idea: Aquaculture is fish farming — raising aquatic organisms in controlled environments. It now provides over 50% of fish for human consumption and is the fastest-growing food production sector.
Advantages of aquaculture
- Reduces pressure on wild fish stocks
- More efficient protein production than land animals
- Reliable, year-round supply
- Can be done in many locations (coastal, inland, urban)
- Provides employment in rural/coastal areas
Disadvantages of aquaculture
- Pollution — waste, antibiotics, and chemicals contaminate water
- Disease — crowded conditions spread parasites and diseases
- Escapees — farmed fish escape and compete with/breed with wild populations
- Feed issues — carnivorous fish (salmon) need wild-caught fish as feed
- Habitat destruction — mangrove removal for shrimp farms
Aquaculture is not automatically sustainable! Farming herbivorous fish (tilapia, carp) is more sustainable than farming carnivores (salmon) that need fish meal.
IB-style question — projected rise in shrimp harvest [1]
A bar chart shows the global farmed-shrimp harvest is 6 million tonnes in 2020 and is projected to reach 19 million tonnes in 2050.
Calculate the projected increase in farmed-shrimp harvest between 2020 and 2050. [1]
How to answer it, step by step
- Increase = new value − old value
• = 2050 figure − 2020 figure
• = 19 − 6 - Subtract
• 19 − 6 = 13 million tonnes
Final answer
'Increase' means subtract the start value from the end value — keep the units (million tonnes), and don't turn it into a percentage unless asked.
IB-style question — why mussels are farmed more than tuna [2]
Global aquaculture produces far more farmed mussels (a mollusc) than farmed tuna (a large marine fish).
Describe two reasons why mollusc aquaculture harvests are so much larger than marine-fish aquaculture harvests. [2]
How to answer it, step by step
- Molluscs are simpler to farm
• They are small and barely move, so need little space and can be packed densely
• They filter-feed on water, so don't need expensive feed - Big fish are hard to farm
• Large marine fish (e.g. tuna) need huge tanks and lots of feed
• This makes them costly and often not economically viable to farm
Final answer
Give two clearly different reasons — one about why molluscs are easy, one about why big fish are hard — not two ways of saying 'molluscs are small'.