General Fisheries Commission for the Mediterranean - GFCM

Winner of the MedFish4Ever Award on innovative practices
in aquaculture research

Innovative saltwater aquaponic system

Institute of Agrifood Research and Technology, Spain

What is the project? 

Despite their sustainability, effectiveness and low cost, most aquaponic systems in operation today are only used on a limited commercial scale. Encouragingly, the new system developed by the Institute of Agrifood Research and Technology(IRTA) of La Ràpita for raising grey mullet (Mugil cephalus), a low trophic species, along with the nutritious culinary delicacy Salicornia (or sea asparagus) shows strong potential for wider application. The aquaponic system is based on the fact that the nutrients in the water come from fish, unlike in hydroponics where they are poured in by people. The fish live in saltwater tanks, while their excrement and unused feed go to another solids tank where they are decanted. The water left over passes through another biological filter where bacteria transform ammonia (toxic to fish) into nitrites, which in turn transform naturally into nitrates. These and other nutrient remains from the feeding system end up in the compartment where the plants are, helping them to grow. Finally, once the water has made its way through the plants, it is pumped – clean – back to the fish tanks and reused.

Why does this matter?   

This prototype is part of the European NewTechAqua project of the H2020 programme, which strives to innovate in sustainable aquaculture production systems. The main characteristic that separates these models is their low installation cost: they use common and even recycled materials, consume minimal electricity, and have the ability to adapt to very diverse environments and situations – including using alternative energy sources such as photovoltaics. The simplicity of the design means it can be adapted for almost any fish and vegetable model, optimizing the space–productivity ratio for species such as Salicornia, tomato or lettuce in combination with flathead grey mullet, trout or seabass, for example.

How is the project impactful?  

The impact of the project is clear from the results. Lettuce was used for the first phase of system testing, and in less than 3 months 90 kg was harvested, an impressive yield of 4–5 kg/m2 achieved during winter without the use of heating or fertilizers. Following these tests, the second phase moved on to high-value Salicornia, which yielded a harvest of 250 kg in 18 m2. This cultivated Salicornia has a much higher nutritional value than wild plants, thanks to its controlled and stable growing conditions. The fish benefit from the cycle, as the plants retain macro and micronutrients that could be toxic to them. It also saves energy, since traditional water recirculation systems need to add extra water to transform these nutrients. Trials to optimize the system to incorporate multiple crops are ongoing, but they already indicate that the concept has a wide potential application.

Location and possibility of replication in the GFCM area of application 

The prototype – a living laboratory – is located at the mouth of the Ebro delta in La Ràpita, Tarragona, Spain. It is a popular tourist area important for both agriculture (rice, citrus fruits, olive trees) and fishing and aquaculture (mussels, oysters, clams, seabream, seabass), and it faces considerable environmental pressure as well as a changing climate. In fact, the United Nations selected it as a case study region for designing alternative low-impact production models such as this one. Similar aquaponics systems could be installed almost anywhere in the Mediterranean and beyond, from urban gardens and peri-urban areas to agricultural parks and regions of the world with few natural resources.