Interrelationships between stress and osmoregulation in Oreochromis mossambicus, an euryhaline fish, and in Cyprinus carpio, a stenohaline freshwater fish.

Transport, handling, hypoxia, confinement, crowding, different habitat and different social interactions, isolated or cumulative, are possible stressors in aquaculture. The effect of stress, if not directly lethal, generally can cause damage to process and product quality in aquaculture. The studies carried out to date have demonstrated that stress is related to energy mobilization and water-mineral balance. The objective of the present study was to verify which effect the stress and the consequent cortisol release produce on plasmatic osmolality of an euryhaline species acclimated to different salinities and of an stenohaline species. A further objective was to study also any possible effects of cortisol release on Na+/K+ ATP-ase activity of the osmoregulatory organs. The literature concerning the effect of this hormone on the main enzyme in active transfer of ions is contradictory