Aquaculture

Aquaculture, sometimes called aquafarming, refers to the controlled cultivation of aquatic organisms including fish, crustaceans, molluscs, algae and a wide range of aquatic plants. It encompasses freshwater, brackish and marine environments and is often contrasted with commercial fishing, which depends on harvesting wild populations. Modern aquaculture ranges from highly controlled land-based systems to sea-based habitats influenced by natural conditions. It is both a major food-production industry and a tool for environmental restoration, species conservation and habitat rehabilitation.

Concepts and Definitions

Aquaculture involves breeding, growing and harvesting aquatic organisms under conditions that involve human intervention and ownership of stock. The Food and Agriculture Organization defines it as farming that includes practices such as stocking, feeding and protection from predators. When practised in the sea, it is often termed mariculture. Pisciculture, focused specifically on fish, is among its most widely known branches. Aquaculture may occur in:
• Onshore systems, such as tanks, ponds, aquaponics units and raceways, where variables including water quality, oxygen, salinity and temperature are closely controlled.• Inshore systems, situated in sheltered coastal or littoral zones where organisms experience semi-natural conditions.• Offshore systems, where cages or enclosures are placed in deeper, more dynamic waters, exposing stock to natural currents and nutrient cycles.
This breadth of practice allows aquaculture to meet diverse objectives—from food production to ecosystem enhancement and the reconstruction of endangered species populations.

Global Growth and Economic Significance

Aquaculture has grown rapidly over recent decades, driven by increased global demand for seafood and the stagnation of wild fisheries. Reported global output exceeded 120 million tonnes in 2019 and rose to more than 130 million tonnes by 2022, with a market value exceeding USD 300 billion. However, data reliability varies, and concerns have been raised about reporting accuracy in some regions.
A persistent challenge in aquaculture is reliance on wild fish for feed, particularly in the farming of carnivorous species such as salmon. Several kilograms of wild-caught fish may be required to produce one kilogram of farmed fish. To address this, alternative feeds based on plants, insects and microbial proteins are under development. As aquaculture expands, its contribution to national economies ranges widely but is often complex to calculate due to limited data.
The industry is significantly affected by climate change, with shifts in water temperature, acidity and weather patterns influencing production systems worldwide.

Historical Context and Domestication

Early enthusiasm for aquaculture gave rise to predictions of a “blue revolution,” mirroring the transformative effects of the twentieth-century Green Revolution in agriculture. While humans have long domesticated terrestrial species, the domestication of aquatic species accelerated only in the twentieth and twenty-first centuries. Around 430 species used in aquaculture have undergone some degree of domestication, with many entering cultivation in the past few decades.
Domestication of aquatic species generally presents fewer risks to humans compared with land animals, which were historically responsible for many major human diseases. Aquaculture has therefore expanded relatively rapidly as scientific understanding and technology have developed.

Environmental and Management Issues

Aquaculture can influence ecosystems both positively and negatively. Beneficial contributions include habitat reconstruction, restocking of endangered species and provision of food with lower land-use demands than terrestrial agriculture. Harmful impacts may arise through:
• Nutrient pollution from uneaten feed and waste• Disease transmission to wild populations• Use of chemicals or antifouling agents• Overreliance on wild fish for feed inputs
Biological controls, such as the use of cleaner fish to reduce sea lice in salmon farms, have become common tools for managing parasitic outbreaks. Spatial models and improved planning techniques help minimise environmental pressures by guiding the placement of farms.
Following restrictions on organotin antifouling agents, researchers are seeking environmentally benign alternatives. Natural compounds show promise, but commercial-scale production remains challenging.

Species Groups

Aquatic PlantsAquaculture of aquatic plants includes microalgae (phytoplankton) and macroalgae (seaweeds). Farmed seaweeds dominate global aquatic plant production and serve as food, fertilisers and industrial raw materials. Production has grown markedly, reaching more than 30 million tonnes by 2016.
Fish FarmingFish farming is the most widespread form of aquaculture and typically involves raising fish in ponds, tanks or ocean enclosures for food. Key species worldwide include carp, salmon, tilapia and catfish. Hatcheries that release juvenile fish into the wild also play roles in supporting recreational fisheries and replenishing natural stocks.
In the Mediterranean, young Atlantic bluefin tuna are captured and fattened in sea cages. Southern bluefin tuna have recently been bred successfully in land-based tanks, marking a significant technical achievement. Salmon farming often uses ocean-based net pens with currents promoting healthy growth, and feeds are formulated to support rapid and reliable development.
Seaweed FarmingSeaweed cultivation is an expanding practice that contributes both food and industrial products. It represents the vast majority of global aquatic plant production.

Key Methods and Technologies

Modern aquaculture uses diverse and increasingly sophisticated methods:
• Aquaponics, integrating fish culture with hydroponic plant production• Integrated multi-trophic aquaculture, combining species such as fish, shellfish and algae to recycle nutrients• Offshore cage farming, using open-ocean environments for large-scale fish production• Hatchery-based enhancement, supporting wild populations and commercial stocks
Technological advances—in monitoring systems, selective breeding, genetics and feed formulation—continue to enhance efficiency and sustainability.

Challenges and Prospects

As aquaculture output has surpassed capture fisheries, its future expansion depends on addressing environmental, social and economic constraints. Key challenges include reducing reliance on wild feed sources, managing disease, improving regulatory frameworks and adapting to climate change. Research into environmentally friendly antifouling materials, microbial feed production and low-impact farming systems is central to improving sustainability.