Effects of acclimation to brackish water on tolerance of salinity challenge by young-of-the- year Adriatic sturgeon (Acipenser naccarii)

The effects of a 24-h salinity challenge in water at 28 g·L–1 on plasma osmotic and ion homeostasis, swimming performance, and exercise respirometry were compared in young-of-the-year Adriatic sturgeon (Acipenser naccarii) maintained in freshwater (FW) or acclimated to brackish water (BW) that was slightly hypertonic to sturgeon plasma at a salinity of 11 g·L–1. Salinity challenge caused a significant increase in plasma osmolality and Na+ and Cl– concentrations in both groups, but this was significantly less severe in the group acclimated to the BW as compared with FW. Salinity challenge elicited a significant and profound decline in maximum sustainable swimming speed (Ucrit) in sturgeon from FW, whereas there was no significant effect on Ucrit in the sturgeon acclimated to BW. A negative linear relationship was revealed between plasma osmolality, Na+ or Cl– concentrations, and Ucrit. These variables appeared to influence Ucrit by increasing costs for locomotion while reducing the sturgeon's capacity for ...