Diadromous sturgeons (group 3), Russian sturgeon (A. gueldenstaedtii), Persian sturgeon (A. persicus), Starred sturgeon (A. stellatus) and Beluga (Huso huso) have the ability to adapt to brackish water (12-18 ppt salinity) as firm osmo-regulators (Krayushkina, 1998). After transferring from freshwater to brackish water, these species support a blood serum osmolarity and ion concentration lower than the water ions and osmolarity in the environmental medium (Amini et al., 2005). The functional levels of osmoregulatory and ion regulatory systems in these species are not identical. The starred sturgeon is more euryhaline than the Russian sturgeon and the Beluga (Krayushkina, 1998).