Plasma cortisol and metabolite level profiles in two isogenic strains of common carp during confinement

A rapid increase in common carp Cyprinus carpio plasma cortisol levels was noted, in two experiments. after 30 mins of a 3 h net confinement, which wa s sustained while the fish ut rr held in the nets. After release from the n ets, cortisol levels returned to control values in I h. Plasma glucose and free fatty acid levels were elevated by the confinement. Glucose was increa sed after 30 min but returned to basal levels after 22 h of recovery while free fatty acids were not elevated until 3 h or confinement and remained hi gh for the duration of the recovery period. After confinement Tor 3 h, plas ma lactate levels were reduced and remained low for a further 1 h. No chang e in either plasma triglyceride or cholesterol levels were found during the study. Confinement had no effect on haematocrit levels but blood haemoglob in levels were reduced. In both experiments hypochloraemia occurred in resp onse to confinement. However, values returned to pre-confinement levels 22 in after confinement. The se results show that rearing isogenic carp strain s, under identical conditions, results in a reproducable response to an acu te stressor and that these carp respond in a similar manner to other teleos t species. (C) 2001 The Fisheries Society of the British Isles.