World aquaculture is a fast growing activity and the control of its waste becomes a key issue. Compared to traditional systems, recirculating systems allow to reduce replacement water and waste volumes. Nevertheless their effluents are more concentrated in dissolved nutrients (nitrate, phosphate). The high rate algae pond (HRAP) is one of the possible treatment technique to remove those nutrients. During this work, three rearing systems: one recycled, one recycled with HRAP and one open as a standard, were operated for one year to assess the impact of: (1) the reuse of treated effluent on survival, growth and nutrition of sea bass (2) the rearing system on fish health using multibiomarkers and trace metals accumulation responses and (3) best conditions for HRAP treatment. HRAP had no major effect on fish global parameters but growth and nutrition were slightly reduced in recirculating circuits compared to the standard. EROD and SOD activities were slightly induced and several metals accumulated in the fishes of the recirculating system, however their concentration remained far lower than the recommended values for human food. SOD induction and main metal accumulation were suppressed in fish from recirculating circuits where water was treated by HRAP. Algae growth and associated nutrients removal are seasonal and are increased by a low algae density and a high renewal rates in HRAP. The measurement of algae photosynthesis showed an inorganic carbon restriction for algae growth in HRAP.
HRAP seems to be an interesting solution to improve fish performances and flesh quality in recirculating systems. In other respects, this work suggests new tools to assess rearing fish health.
World aquaculture is a fast growing activity and the control of its waste becomes a key issue. Compared to traditional systems, recirculating systems allow to reduce replacement water and waste volumes. Nevertheless their effluents are more concentrated in dissolved nutrients (nitrate, phosphate). The high rate algae pond (HRAP) is one of the possible treatment technique to remove those nutrients. During this work, three rearing systems: one recycled, one recycled with HRAP and one open as a standard, were operated for one year to assess the impact of: (1) the reuse of treated effluent on survival, growth and nutrition of sea bass (2) the rearing system on fish health using multibiomarkers and trace metals accumulation responses and (3) best conditions for HRAP treatment. HRAP had no major effect on fish global parameters but growth and nutrition were slightly reduced in recirculating circuits compared to the standard. EROD and SOD activities were slightly induced and several metals accumulated in the fishes of the recirculating system, however their concentration remained far lower than the recommended values for human food. SOD induction and main metal accumulation were suppressed in fish from recirculating circuits where water was treated by HRAP. Algae growth and associated nutrients removal are seasonal and are increased by a low algae density and a high renewal rates in HRAP. The measurement of algae photosynthesis showed an inorganic carbon restriction for algae growth in HRAP.
HRAP seems to be an interesting solution to improve fish performances and flesh quality in recirculating systems. In other respects, this work suggests new tools to assess rearing fish health.
