Integrated Multi-Trophic Aquaculture Systems (IMTA)

The aquaculture production has grown steadily owing to the dramatic expansion in this sector worldwide. During the past three decades production increased from 6.2 million t in 1983 to 70.2 million t in 2013 (FAO, 2015). Aquaculture surpassed the supplies from the capture fisheries and contributed nearly 51% to the global fish production in 2013. This achievement was possible mainly because of the commercialisation of farmproduced aquatic groups such as the shrimps, salmon, bivalves, tilapia and catfish. This sector also benefitted from the significant production of certain low-value freshwater species through integrated farming, intended for domestic production. This growth in marine aquaculture industry, has introduced many apprehensions about the environmental impacts from aquaculture waste. Intensive finfish farming in cages can release significant quantities of nutrients to the farm site, from uneaten feed, faeces and excretory products. These metabolic wastes from farm effluents, mostly ammonia, may contribute to increased nutrients and localised eutrophication in the farm. One of the major challenges for the sustainable development of aquaculture industry is to minimise environmental degradation concurrently with its expansion. Though majority of aquaculture production originate from extensive and semi-intensive farming systems, the recent increase in intensive farming of marine carnivorous fed-species is associated with environmental concerns. Integrating waste generating (fed) and cleaning (extractive) organisms in mariculture is a practical technology for sustainable mariculture. In a balanced integrated system, aquaculture effluents can be converted into commercial crops while restoring water quality