By: Dr Mustapha ABA, Aquaculture Researcher, Fish Nutrition. Morocco.
Aquaponics is a technique that takes advantage of the symbiotic association between aquatic animals and plants by creating an efficient and unconventional crop production system resulting in the production of both fish and vegetables or fruit. This system works in such a way that fish waste and residues are nutrients that fertilize the plants, which in turn clean the fish water, making it reusable. This system is based on the fusion of aquaculture and hydroponics.
According to FAO, aquaculture is the farming of aquatic organisms in controlled or semi-controlled environments. Several activities are developed within aquaculture, including: fish production, shellfish farming, and the cultivation of aquatic plants. Representing a source of food and income for the population. The aquaculture product is an alternative livelihood for human beings, guaranteeing a quality diet.
Aquaculture is an ancient practice whose origins date back to Egypt and China, where the fish farmed were species such as tilapia and carp. In Africa, aquaculture is gaining momentum through political initiatives such as the establishment of aquaculture development agencies in several African countries and the role aquaculture can play in food security, income generation and poverty alleviation.
According to the FAO (2018), aquaculture has surpassed fisheries production and is currently responsible for half of the world’s fish trade, but the activity has its challenges. According to the book Climate Impacts on Fisheries and Aquaculture (FAO, 2018), the climate changes that are currently occurring are causing physical changes, for example, in water temperature and pH, which will have a negative impact on aquaculture.
In addition, aquaculture depends on the supply of nutrients to the animals, which produce effluents and wastes through natural survival processes, generating negative impacts on the aquatic system and environment. These pollutants must be removed through periodic water exchange, followed by good environmental management if the system is to be successful. This impact on the aquaculture production system can cause a decrease in dissolved oxygen by increasing organic matter and phosphorus and nitrogen concentrations, which are responsible for the eutrophication of aquatic environments. In aquaponics, these discharges are a nutrient source for plants.
Figure 1 shows the excretion rates of phosphorus retention and nitrogen ingested by fish through food. Figure 1 – Phosphorus and nitrogen retention and excretion.
Hydroponics is conceptualized in agricultural production without land use, through solutions that provide the nutrients necessary for plant sustenance and development.
Basically, a reservoir is needed to store water with the mineral elements essential for plant growth, whose roots are immersed in the solution by absorbing the nutrients present in the water.
The nutrient solution present in the reservoir, thanks to a water pump, circulates in the container of the plant’s crop, where the nutrients are absorbed by the plant roots and the unused water returns to the container, as shown in Figure 2.
Aquaponics is a technique that integrates aquaculture and hydroponics so that the two systems complement each other in a symbiotic way in a beneficial relationship.
Aquaponics is the combination of recirculating aquaculture and hydroponics. In aquaponics, the nutrient-rich water that results from the production of toxic fish waste is transmuted into organic matter and non-toxic fish products, providing a source of nutrients for plants. Beneficial bacteria convert the toxic components of the fish waste into a form of nutrient that can be used by plants. A natural microbial process that keeps fish and plants healthy and helps maintain an environment in which plants and fish can thrive (see Figure 3).
As the population grows, the demand for food increases, so agricultural activities tend to expand. Since the agricultural sector is currently responsible for 70% of the world’s water consumption, 60% of the water used is wasted due to the lack of localized irrigation. At present, there is growing concern about the increasing scarcity of drinking water, given that water is essential for the survival of all living beings. Mitigating water wastage in food production is one of the alternatives that can be achieved through aquaponics. This type of system, which is already being used in many countries, has had encouraging results, and the amount of water needed for this type of system is extremely low, allowing better optimisation of water use, and the plants and fish share the same water, and the recirculation of water is done in such a way that waste is minimal, which radically reduces the discharge of fish effluents into the aquatic environment.
The aquaponic system, the result of a sustainable balance between fish and plant, this technique of integrating the production of fish (aquaculture) and soil-less plants (hydroponics) in a closed system, where the metabolic waste of the fish (mainly nitrogen) is used by the plants to grow, can be an alternative in Africa to produce two foods, fish and vegetables for example by exploiting a small amount of water, which will contribute to sustainable development in Africa.