Integrated multi-Trophic Aquaculture in ponds: what environmental gain? An LCA point of view

Aquaculture faces a double challenge produce more to sustain growing demand for aquatic products and respect the environment. For several years, Integrated MultiTrophic Aquaculture (IMTA) has gained worldwide attention. IMTA is based on integrated cultivation of aquatic organisms from different but complementary trophic levels. The objective of this study was to assess environmental performances of pond-IMTA systems based on freshwater polyculture experiments in earthen ponds conducted in Romania, France and Indonesia that explored different ways to combine fish and plants. In each experiment, the IMTA system was compared to a conventional or traditional system for the country (carp polyculture in Romania, intensive polyculture in France and gourami monoculture in Indonesia). Environmental impacts of IMTA systems differed among case studies. In Romania, environmental impacts also differed between years: IMTA system had higher impacts than the traditional one in 2016 but has lower impacts in 2017. In France, conventional system had lower cumulative energy demand, eutrophication and NPPU than semi-intensive and IMTA system, the latter had the highest values of these impacts. However, for climate change the conventional system has higher impact than IMTA and semi-intensive system. In Indonesia, IMTA system had lower impacts than the tradional one. The environmental impacts estimated in this study illustrate the variability in the responses of IMTA systems. Impacts of agricultural systems depend on system productivity and the amounts of inputs embodied in the system. IMTA is expected to provide improvements such as a decrease in input use such as feed, increase in fish yields, and/or decrease in emissions per unit mass of fish produced. Depending on the practices, increasing the number of species or their organization through IMTA practices can decrease environmental impacts, especially local impacts such as eutrophication, compared to classic practices. Production and use of fish feed is one of the main causes of environmental impacts. Based on our results, IMTA practices can improve resource use and decrease the overall impact of aquaculture. Any increase in inputs used to improve nutrient recycling must also increase productivity to ensure a decrease in impacts per unit mass of fish. Certain impact categories that can describe consequences of IMTA systems more completely are lacking, especially those related to diversity, particularly biodiversity.