Integrated Multi-Trophic Aquaculture (IMTA) is defined as a balanced system where the culture of fed organisms (mainly fish and shrimps) is combined with the culture of organic matter extractive species (shellfish, polychaetes, and holothurians) and dissolved inorganic nutrients extractive species (seaweeds). This production model transforms the waste produced by the traditional aquaculture into animal and vegetal biomass.
Researchers of the National Center of Mariculture (NCM) in Eliat, Israel, have conducted a study for evaluating the co-culture of flathead grey mullet (Mugil cephalus) and gilthead sea bream (Sparus aurata) in land-based IMTA system to assess the growth, survival, and efficiency on nitrogen assimilation of both species. Grey mullet and sea bream were cultured inthe same tank, sea breams were stocked in floating rectangular cages while grey mullet were stocked directly into the tanks. The sludge generated by seabreams serves as feed for the grey mullets. Parallelly, Sea bream and grey mullet were cultured by separate for comparative purposes.
The growth and survival of sea bream cultured in co-culture tanks were similar to those cultured by separate. On the other hand, the performance of grey mullets cultured in co-culture was lower compared with those cultured by separate. However, from the overall point of view, the co-culture of sea bream and grey mullet increased the biomass of fish by 5.6-8.3%, increase the efficient assimilation of nitrogen by fish in 5.7-8.3%, reduced the feed factor conversion by 12-15% and reduced the amount of sludge by 85% and the amount of nitrogen in the sludge by 98%; nevertheless, the dissolved nitrogen emissions increase by 10%. In addition to the advantages mentioned above, the researches explain that the incorporation of grey mullet in co-culture into the IMTA presents two great advantages more: (i) the sludge treatment costs decrease and (ii) eventually the sales of grey mullet could generate an extra income for the farmers.