The Israeli Journal of Aquaculture - Bamidgeh 51(1), 1999, 10-16
DESIGN OF A STRESS MODEL IN THE HYBRID BASS
(MORONE SAXATIUS X MORONE CHRYSOPS)
O. Melamed, B. Timan, R. R. Avtalion and E.J. Noga
1 - Laboratory of Fish Immunology and Genetics, Faculty of Life Sciences, Bar llan University
Ramat Gan, 52900, Israe!
2 - North Carolina State University, College of Veterinary Medicine, 4700 Hillsborough Street
Raleigh. NC 37606, USA
(Received 23.4.98, Accepted 2.12.98)
The effects of different stress-causing agents such as hypoxia, temperature shift, netting, bleeding and air exposure, as monitored by measuring blood glucose alterations, were determined in hybrid bass (Morone saxatillis x M. chrysops). Results obtained using a multifactorial stress mode (netting, bleeding and air exposure) showed that elevation of blood glucose was linearly correlated with progressive stress intensity. By using a simpler laboratory model based on air exposure only, it was shown that bleeding at the beginning of the experiment had no significant effect on final glucose levels measured after 7 hours. The maximal blood glucose level in all stress procedures ranged 326 -392 mg/dl. The higher values were followed by severe signs of stress and even mortality. Hypoxic water caused rapid stress, with 326 mg/dl blood glucose in only 90 minutes. Conversely, a slowly developing stress response was achieved by abruptly lowering the temperature by 7°C. The air exposure model was also used for testing lysozyme activity during stress. Contrary to glucose, plasma lysozyme was significantly lower in stressed than in unstressed fish. While no significant differences were evident in lymphoid tissues at 7 h, lysozyme activity increased significantly after 24 h in the spleen and posterior kidney, but not in the anterior kidney. A possible explanation of this phenomenon is discussed.