ROUTINE METABOLISM AND DIGESTIVE ENZYMATIC ACTIVITY IN JUVENILE TILAPIA (Oreochromis mossambicus x Oreochromis niloticus) ACCLIMATED TO DIFFERENT SALINITIES

In the present study juvenile of hybrid tilapia (O. mossambicus x O. niloticus) were used; which were acclimated to different salinities. The effect of water salinity on the routine metabolism of juvenile of this hybrid at 0, 10, 20, 30 and 35 practical salinity units (psu)were evaluated, with maximum rates of oxygen consumption of 0.230 +/- 0.063, 0.177 +/- 0.050, 0.244 +/- 0.073, 0.194 +/- 0.045 and 0.172 +/- 0.037 mg O2/g/h in dry matter, respectively. The digestive enzymatic activity like- trypsin and amylase were affected significantly with water salinity. Maximum activity like- trypsin was 2.1 +/- 0.29 U/mg protein in freshwater, this decreased at 35 psu to 0.4 +/- 0.07 U/mg protein. Amylase activity diminished while the salinity increased, from 0.87 +/- 0.15 U/mg protein in freshwater to 0.27 +/- 0.00 U/mg protein at 35 psu. Under the conditions of this study the energetic expense and the digestive enzymatic activity of juvenile tilapia were significantly affected by the salinity.