The dual objective of sustainable aquaculture, i.e., to produce food while sustaining natural resources is
achieved only when production systems with a minimum ecological impact are used. Recirculating aquaculture systems (RASs) provide opportunities to reduce water usage and to improve waste management
and nutrient recycling. RAS makes intensive fish production compatible with environmental sustainability. This review aims to summarize the most recent developments within RAS that have contributed to
the environmental sustainability of the European aquaculture sector. The review first shows the ongoing expansion of RAS production by species and country in Europe. Life cycle analysis showed that feed,
fish production and waste and energy are the principal components explaining the ecological impact of
RAS. Ongoing developments in RAS show two trends focusing on: (1) technical improvements within the
recirculation loop and (2) recycling of nutrients through integrated farming. Both trends contributed to
improvements in the environmental sustainability of RAS. Developments within the recirculation loop
that are reviewed are the introduction of denitrification reactors, sludge thickening technologies and the
use of ozone. New approached towards integrated systems include the incorporation of wetlands and
algal controlled systems in RAS. Finally, the review identifies the key research priorities that will contribute to the future reduction of the ecological impact of RAS. Possible future breakthroughs in the fields
of waste production and removal might further enhance the sustainabilty of fish production in RAS