Salt stress and resistance to hypoxic challenges in the common carp (Cyprinus carpio L.)

Long term exposure to brackish water (171 mM NaCl) affected the capacity of common carp Cyprinus carpio to deal with hypoxic conditions and the critic al oxygen concentrations for oxygen consumption increased. In addition, reg ulation of ammonia excretion was lost. The cytosolic phosphorylation potent ial (the index of the energy status of a cell in terms of potential transfe rable phosphate groups) in the lateral muscle on the other hand remained re latively unaffected, indicating that oxygen transport to the tissues was no t severely compromised. It appears that exposure to brackish water reduces the capacity of common carp to cope with hypoxic conditions mainly because of the high energetic cost of hyperventilation under conditions where energ y stores are depleted, and not because of any impeded oxygen transport mech anisms. (C) 2000 The Fisheries Society of the British Isles.