Comparison of digestive enzyme activities in the larvae of Siberian sturgeon (Acipenser baeri Brandt) and Russian sturgeon (Acipenser gueldenstaedti Brandt) back cross hybrids

The activities of digestive enzymes were measured in two reciprocal sturgeon hybrids: Siberian sturgeon (Acipenser baeri Brandt) x Russian sturgeon (Acipenser gueldenstaedti Brandt) x Siberian sturgeon (SR.S), and Siberian sturgeon (Acipenser baeri Brandt) x Russian sturgeon (Acipenser gueldenstaedti Brandt) x Russian sturgeon (SR.R) from 3 to 10 weeks of rearing. After a diet change in the 4th week from ASTA-AC to trout starter Aller-Aqua, both hybrids showed a decrease in the activity of lipolytic (about 20%) and amylolytic enzymes (2- and 5-times for SR.R and SR.S, respectively) in the 5th week. In both hybrids acidic proteases were more active than alkaline ones. The ratio of acidic/alkaline protease activities was considerably higher in SR.R than SR.S, beginning from the 4th week of rearing. Its highest values were observed in week 9 (3.43 for SR.R and 1.89 for SR.S). Such a pattern of enzymatic activities explains the higher growth rate of SR.R, compared with SR.S observed from the 5th week of experiment.