Microalgae phycotechnology for nutrients valorization in marine fish farming: the SUNRAS project

Abstract

Fisheries and aquaculture are a major source of employment and income on which the livelihoods of 10-12% of the world's population are based. However, the production process has to be improved in order to increase the sustainability. The ratio of Kg of wild fish needed to produce one kilogram of farmed fish called Fish-In FishOut (FIFO), the carbon and water footprint and the discharge of nitrogen and phosphorus into the environment are certain points that must be resolved to increase the sustainability of this activity. Globally, the FIFO value of marine fish has been declining to 0.53 in 2015 (IFFO, 2017). This decrease is due to an increase in alternative sources of fish meal and fish oil such as oleaginous seeds, rich in Poly-unsaturated fatty acids (PUFAs). Microalgae and aquaculture have traditionally been grown in both freshwater and seawater, two activities that have always been linked due to microalgae are part of the food chain as primary producers and feed different species in larval stages. They are now playing an increasingly important role in the world of wastewater treatment (Arbib et al., 2014) but in the field of aquaculture, this technology is less technologically advanced and often linked to extensive systems (Milhazes-Cunha, 2017). Since the main problem of alternative sources of proteins and fatty acids of terrestrial origin do not have adequate profiles, some authors (Madeira et al., 2017; Pérez-Velázquez, 2018) propose the use of microalgae as a potential substitute for fish meal and fish oil. Therefore, in the SUNRAS project, a thorough study has been carried out to find out the feasibility of using microalgae based biotechnology to recover nutrients from aquaculture streams as well as the use of the microalgae biomass as an additive of fish feed.