The effects of capture, handling, confinement and ectoparasite load on plasma levels of cortisol, glucose and lactate in the coral reef fish Hemigymnus melapterus

Tropical labrids Hemigymnus melapterus sampled underwater had low plasma le vels of cortisol, glucose, and lactate. Plasma cortisol levels were elevate d by capture stress within 5-6 min, while glucose and lactate levels were n ot. Plasma levels of cortisol and glucose increased after 2-4h of handling and transport to the laboratory. Levels of cortisol and glucose fell with l aboratory acclimation back to values similar to those found in wild fish. P arasitism by gnathiid isopods across an order of magnitude of isopod number s had no effect on plasma levels of cortisol or glucose. Thus, H. melapteru s has a stress response similar to that shown by temperate species, and rel atively high parasite loads are not apparently stressful to fish in the wil d. This may be related to the counterproductive effects of physiological st ress responses on the immune system or behaviour-modulated processes that c ounter parasitic invasion. (C) 2000 The Fisheries Society of the British Is les.