Phosphorus Waste Production in Fish Farming a Potential for Reuse in Integrated Aquaculture Agriculture

The increase in the size of the world'spopulation, together with the rise in average per capita fish consumption and the demand for fish, the role that aquaculture plays in ensuring food security, and to preserve marine resources has led to development of this sector in the world over the last few decades (FAO, 2020).

One of the consequences of the expansion of aquaculture is the significant increase in the production of faecal and metabolic waste from feed in farming systems. The main pollutants involved in these aquaculture effluents, are phosphorus (P), nitrogen (N) standout as important contributors to the eutrophication process of the aquatic environment, leading to negative impacts on the environment, (Lazzari and Baldisserotto, 2008). Among the nutrients lost from diets, phosphorus is the most critical, is the main factor of pollution in aquaculture since it influences directly the eutrophication process (Carpenter et al., 20O8; Morales et al, 2015; Han et al., 2016; Wang et al., 2017, Sugiura, 2018).

In this context, this forces us to rethink waste management with a sustainable vision, operating systems that allow us to reuse nutrients from effluents generated by fish farming (Carpenter and Bennett, 2011), in order to take advantage of the phosphorus nutrients present in aquaculture effluents, especially as the growing global demand for food results in a steady increase in the demand for P, which is expected to increase the cost of P fertilizers in the future (Ashley et al, 2011; Scholz and Wellmer, 2015; Geissler et al., 2019 ).

From this need stems the concept of Integrated Multi-Trophic Aquaculture (IMTA) systems, which allow the co-production of food or other products through the recycling of aquaculture wastes in order to ensure the environmental sustainability of the sector (Troell et al., 2009; Barrington et al., 2009; Chopin, 2013).

The integration offish farming systems with the production of vegetables or fruits are commonly cultivated by integrating aquaculture with agriculture; in agricultural irrigation or aquaponics, is already well established in freshwater, is a sustainable and productive approach, inline with the principles of Integrated Multi-Trophic Aquaculture (IMTA), applying ecological concepts and principles of agro-ecology, which can therefore play an important role in building resilience and adapting to climate change, in addition to food security (FAO, 2019). Integrating aquaculture into farming systems can improve productivity, water use efficiency and overall environmental sustainability (Ingram et al., 2000), reduce the use of chemical fertilizers (Rejesus et al., 2013), and promote ecological, social and economic benefits (Halwart et al., 2003; Aba Mustapha and El Bakali, 2020).

Fish feeds contain Phosphorus and are essentially the only significant source of Pin aquaculture (Van Ginkel et al.., 2017; Strauch et al, 2018), although the importance of phosphorus nutrition is well known to fish nutritionists, mainly because of its effect on bone development and energy kinetics in the cell (Lall, 2002 ; NRC, 2011), in addition to its biological importance for fish, it is well established that excess phosphorus in fish feed can promote eutrophication of aquatic environments, few studies are available on phosphorus-rich aquaculture effluents used by plants by integrating aquaculture into agriculture in order to contribute to the sustainability of aquaculture production. Due to the lack of information on mineral nutrition, in particular phosphorus, and its importance for both fish and plants, and for the beneficial use offish feed waste, we purpose this Review article which aims to gather, analyse and synthesise information on phosphorus nutrition in fish feed, with the aim of presenting guidelines for the use of this mineral responsible for aquatic pollution as a fertiliser in the integrated aquaculture agriculture system.