Responses of beluga (Huso huso) to salinity exposure: a laboratory evaluation of the effect of field-based salinity levels on osmoregulatory characteristics and growth performance

There is a need for a better understanding of how sturgeon, especially hatchery reared juveniles, respond to salinity challenges. Therefore, here we examined the effects of different field-based salinities (Freshwater [FW] (0.5), 3, 6, 9 and 12 ppt) on osmoregulatory characteristics and growth performance of juvenile beluga sturgeon, Huso huso, (22.1±1.1 g body weight) over a 60-day period. Survival rate was relatively high in all treatments although there was a sign of adverse effects of salinity on the survival as fish at 12 ppt salinity. Growth performance was better in fish reared at 3 ppt, followed by 6, 9 and 12 ppt. Overall, an increase in plasma sodium, potassium, calcium, magnesium and glucose levels was found in association with the increase of salinity, while the FW control group maintained basal levels. Haematocrit levels were also affected by the salinity and the observed levels in FW, 3 and 6 ppt salinities were lower than other salinity concentrations. The results indicated that the beluga sturgeon juveniles are able to survive and acclimate to moderate salinities. Here, we also discussed the importance of evaluating and comparing specific mechanisms of acclimation in populations across brackish waters of the southern Caspian Sea as such investigations may aid and improve aquaculture strategies.