In freshwater aquaculture, a more isosmotic environment achieved through salinity control may favor fish growth since less energy would be spent for the osmoregulatory process. A 57-day experimental trial was conducted to study aquaponics on-demand coupled system using lambari (Astyanax lacustris) and mustard (Brassica juncea), species reported as tolerant to slightly saline conditions. The mustard was cultured as microgreens given their high sales price, short culture cycle and low nutrient demand. Two treatments (1.0 and 2.0 g NaCl L-1) with four replicates each, were established. An aquaponics on-demand control without salt addition (0) and a hydroponic control (MHy) for the microgreens were also settled, each one with four replicates. During the trial, one lambari and five microgreen culture cycles (9 day each) were completed. At the end of the trial, the lambari (Table 1) and all the microgreen cycles (Table 2 presents only cycles with the highest and lowest microgreen harvests) performances in the 1.0 and 2.0 treatments were statistically similar to the controls (ANOVA, p>0.05). However, lambari asymptotic weight was achieved earlier in the 2.0 treatment compared with the control and the 1.0 treatment (Fig.1).
In conclusion, the use of slightly saline water (2g NaCl L-1) in aquaponics on-demand coupled systems may accelerate lambari growth without compromising mustard microgreen production if compared with the performance on RAS (0g NaCl L-1) and hydroponic systems, respectively.
Funding agencies: FAPESP, grants 2018/23658-5, 2018/23605-9 and 2017/50431-9, CNPq, grants 139130/2020 and 311108/2017-2.