Ambient salinity and osmoregulation, energy metabolism and growth in juvenile yellowtail kingfish (Seriola lalandi Valenciennes 1833) in a recirculating aquaculture system

The effects of salinity on plasma osmolality, branchial chloride cell density, feed consumption and conversion and growth performance of yellowtail kingfish (Seriola lalandi) were evaluated. Fish (11.6±0.6g) were kept for 29days at 14, 18, 22, 26 (experimental) and 30gL^-1 (control) salinity in independent, pilot-scale recirculation aquaculture systems. No differences in plasma osmolality or chloride cell numbers in gills were observed, pointing to a strong osmoregulatory capacity in the juveniles. Fish at 14, 18 and 22gL^-1 (7.61±0.19, 7.61±0.01 and 7.61±0.13% day^-1, respectively) had higher growth rates than fish at 26 and 30gL^-1 (7.10±0.05 and 6.97±0.06% day^-1 respectively). The higher growth rate at lower salinity resulted from increased feed intake; feed conversion was not different. An evaluation of the impact of salinity on growth rate of on-growing stages (till market size) seems warranted to assess whether the profitable effects of low salinity persist in later stages of this important aquaculture species.