Effect of acclimation temperature on the acute stress response in juvenile Atlantic cod, Gadus morhua L., and haddock, Melanogrammus aeglefinus L.

Juvenile Atlantic cod (Gadus morhua L.) and haddock (Melanogrammus aeglefinus L.) were subjected to 30 s air exposure stressors following acclimation to 4, 10 and 14 and 4, 8 and 14 degrees C respectively. Both species responded to the stressor with increases in plasma cortisol at all temperatures tested. At 14 degrees C cortisol levels peaked within 1 h post-stressor, and returned to pre-stressor levels within 24 h. In contrast, at 4 degrees C, peak cortisol levels were not attained until 6 h post-stressor in haddock and remained elevated beyond 24 h in both species. The rate of plasma glucose accumulation was greater at higher temperatures in both species and no increase was seen at 4 degrees C. Lysozyme activity in cod, in response to the stressor, was lower than the values reported for some other species and increased slightly at 14 degrees C. The results show that cod and haddock acclimated to different temperatures respond to common, acute stressors in a manner similar to other teleosts.