Effects of salinity on physiological conditions in juvenile common snook Centropomus undecimalis

This study describes the effects of different salinities on oxygen consumption, ammonia excretion, osmotic pressure, apparent heat increment, postprandial nitrogen excretion, and oxygen:nitrogen ratio in juvenile common snook Centropomus undecimalis. Oxygen consumption of fish fasting and fish feeding was statistically different in relation with salinity. Fish maintained at 0, 25, and 35 ppt invested more energy processing feed than fish maintained at 12 ppt. Fasting fish had lower ammonia excretion than feeding fish and excretion was reduced at high salinities. Snook can change the energetic substrate in function with salinity, from a mixture of protein and lipids and carbohydrates at 35 ppt to a more acute preference for proteins at lower salinities. This species changes osmotic plasma concentrations at extreme experimental salinities. The different salinities were the snook inhabits (0-36 ppt), have a direct effect on the physiology, inducing changes on the oxygen consumption, nitrogen excretion, changes on the energetic substrate and plasma osmotic pressure.