STRESS AND DOMINANCE IN A SOCIAL FISH

Many aspects of reproductive physiology are subject to regulation by s ocial interactions. These include changes in neural and physiological substrates of reproduction. How can social behavior produce such chang es? In experiments reported here, we manipulated the social settings o f teleost fish and measured the effect (1) on stress response as refle cted in cortisol production, (2) on reproductive potential as measured in production of the signal peptide, gonadotropin-releasing hormone, and (3) on reproductive function measured in gonad size. Our results r eveal that the level of the stress hormone cortisol depends critically on both the social and reproductive status of an individual fish and on the stability of its social situation. Moreover, the reproductive c apacity of an individual fish depends on these same variables. These r esults show that social encounters within particular social contexts h ave a profound effect on the stress levels as well as on reproductive competence. Social behavior may lead to changes in reproductive state through integration of cortisol changes in lime. Thus, information ava ilable from the stress pathway may provide socially relevant signals t o produce neural change.