5. Conclusions
‘Producing more food from the same area of land while reducing
the environmental impacts requires what has been called sustainable intensification’ wrote Godfray et al. (2010)in a recent review
about the challenge of feeding 9 billion people. The key question
is how can more food (in the scope of this review, more fish)
be produced sustainably? Considering all aquaculture production
systems in use today, RAS offers the possibility to achieve a high
production, maintaining optimal environmental conditions, securing animal welfare, while creating a minimum ecological impact. At
present, the use of RAS is growing in Europe, for grow-out of freshwater (eel and catfish) and marine species (turbot, seabass and sole)
but also for fingerling production of both freshwater and marine
species. Recent research aiming to improve water treatment efficiency (denitrification reactors, sludge thickening technologies and
ozone) allows reducing water refreshment rates, creating nearly
closed systems, producing a small quantity of an easy to treat and
valuable waste product for use in IAA or IMTA systems. Despite the
recent developments that will certainly foster the environmental
sustainability of RAS, the potential accumulation of substances in
the water as a consequence of reduced water refreshment rates may
pose new challenges. A deeper understanding of the interaction
between the fish and the system will help facing these challenges.