EFFECTS OF TEMPERATURE AND SALINITY ON OXYGEN-CONSUMPTION AND AMMONIA-N EXCRETION OF JUVENILE PENAEUS-JAPONICUS BATE

Both oxygen consumption (O2 mg/g/h) and ammonia-N excretion rates (mug/g/h) of Penaeus japonicus Bate juveniles (0.220 +/- 0.051 g) increased with an increase of temperature in the range of 15-35-degrees-C at four salinity levels (15, 20, 25 and 30 parts per thousand). Oxygen consumption decreased with increase of salinity in 15 and 25-degrees-C; however, differences in oxygen consumption among salinity treatments were not significant at 35-degrees-C. Ammonia-N excretion of shrimp significantly decreased with an increase of salinity in all temperatures tested. Relationships among oxygen consumption (OC), ammonia-N excretion (AE), temperature (T), salinity (S) and exposure time (t) are as follows: OC = - 0.0359 + 0.0235 T - 0.0024 S - 0.0043 t (r2 = 0.7464), and AE = 5.4183 + 2.2379 T - 1.2731 S - 0.2123 t (r2 = 0.7939). The O:N ratio suggested a shift of nutrient utilization from protein-dominated to lipid-dominated metabolism for P. japonicus, when they were subjected to increased salinity of 30 parts per thousand at 15-degrees-C.