Effects of acclimation to brackish water on the growth, respiratory metabolism and swimming performance of young-of-the-year Adriatic sturgeon (Acipenser naccarii)

Specific growth rates, exercise respirometry, and swimming performance 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. Specific growth rate was significantly (17%) lower in BW than in FW. Sturgeon in BW also had a significantly (30%) higher standard metabolic rate than those in FW. In both groups, the relationship between swimming speed and oxygen uptake was described equally well by a linear or exponential equation, with a power relationship between swimming speed and net cost of locomotion and a linear relationship between tailbeat frequency and swimming speed. However, sturgeon in BW exhibited higher mean total oxygen uptake, net costs, and tailbeat frequencies than the FW group at any given swimming speed. There were, however, no differences in aerobic scope or maximum sustainable swimming speed between the FW and BW groups because the BW group exhibited a compensatory increase in active metabolic rate and maximum tailbeat frequency. The results indicate that FW is a more suitable environment than mildly hypertonic BW for young-of-the-year Adriatic sturgeon.