Aquaculture is the farming of aquatic organisms, including fish, molluscs, crustaceans and aquatic plants, under managed conditions. It works by controlling factors such as stocking, feeding, water quality, breeding and harvesting to increase food production.
Level: SL and HL
Subtopic: 4.3 Aquatic food production systems
How Aquaculture Works
Aquaculture can be analysed as an open system with inputs, storages, processes and outputs. Inputs may include juvenile organisms, feed, oxygen, water, labour, energy and medicines. The organisms grow by converting food into biomass, which is eventually harvested as an output.
| Aquaculture system | How it operates | Example organisms |
|---|---|---|
| Sea cages | Enclosures allow surrounding seawater to flow through | Salmon, sea bass |
| Ponds | Managed freshwater or brackish-water bodies contain stocked organisms | Carp, shrimp |
| Recirculating systems | Water is filtered, treated and reused in tanks | Trout, tilapia |
| Shellfish or seaweed farms | Organisms obtain nutrients directly from the surrounding water | Mussels, oysters, kelp |
Aquaculture can increase food security, create employment and reduce harvesting pressure on wild populations. However, intensive systems may release uneaten feed, faeces and chemicals, causing nutrient enrichment and water pollution. Disease, parasites, escaped farmed organisms and demand for fish-based feed can also affect wild ecosystems.
For example, Atlantic salmon farming in Norway uses coastal sea cages and controlled feeding to produce large quantities of fish. Nevertheless, waste discharge, escaped salmon and sea lice can affect wild salmon populations, requiring monitoring and regulation.
A common misconception is that aquaculture is automatically sustainable. Sustainability depends on stocking density, feed source, pollution control, energy use, species choice and regulation; benefits and costs may also be distributed unequally among companies, workers and coastal communities.
