The impact of acute salinity exposure and temperature on the survival, osmoregulation, and hematology of juvenile shortnose sturgeon (Acipenser brevirostrum)

Juvenile shortnose sturgeon (Acipenser brevirostrum Lesueur, 1818) were exposed to seawater and freshwater for 24 h to evaluate the osmoregulatory capabilities over a seasonal temperature gradient (5, 10, 15, 20 degrees C). Additionally, juveniles were exposed to 5 degrees C seawater and freshwater over 72 h to evaluate survival and osmoregulatory capacity under cold water conditions. Osmoregulatory capability was evaluated using standard metrics: survival rate, mass loss, plasma chloride ion (Cl-) concentrations, osmolality, oxygen-carrying variables, and energy metabolites. Three mortalities occurred following 24 It exposure to 20 degrees C seawater (73% survival) and one mortality occurred within 72 h in 5 degrees C seawater (89% survival). Plasma Cl- concentrations and osmolality were elevated in seawater-exposed juveniles at every exposure time, regardless of temperature. The least mass was lost in juveniles exposed to 5 and 10 degrees C seawater, versus 15 and 20 degrees C seawater. Low mass loss is likely due to a lower metabolic rate and lower ventilation, which would slow the rate by which osmotic stress would occur under cold conditions