Does socially induced stress in rainbow trout cause chloride cell proliferation?

At the end of a 2-week confinement period, subordinate rainbow trout Oncorh ynchus mykiss had significantly higher circulating concentrations of plasma cortisol than did the dominant fish with which they were paired. Physiolog ical effects linked to elevated plasma cortisol concentrations in subordina te fish included loss of weight and a lowering of condition factor. However , there were no significant differences in gill epithelium chloride cell nu mbers or blood plasma ion concentrations between dominant and subordinate f ish. It is concluded that elevated plasma cortisol concentrations elicited by the social stressors of the present study did not cause proliferation of chloride cells. (C) 2000 The Fisheries Society of the British Isles.