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

At the end of a 2-week confinement period, subordinate rainbow trout Oncorhynchus mykiss had significantly higher circulating concentrations of plasma cortisol than did the dominant fish with which they were paired. Physiological effects linked to elevated plasma cortisol concentrations in subordinate fish included loss of weight and a lowering of condition factor. However, there were no significant differences in gill epithelium chloride cell numbers or blood plasma ion concentrations between dominant and subordinate fish. It is concluded that elevated plasma cortisol concentrations elicited by the social stressors of the present study did not cause proliferation of chloride cells.