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Breeding Tubercles, Papillomatosis and Dominance Behaviour of Male Roach (Rutilus rutilus) During the Spawning Period


Raine Kortet, Neurobiology, Physiology & Behavior, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA. E-mail:


We studied the relationship between the breeding tubercle ornamentation (i.e. skin roughness) and male pre-spawning dominance and courtship behaviour in roach (Rutilus rutilus) within an experimental laboratory system. Sexually mature fish were caught during their migration to their spawning pond and their behaviours were studied in an artificial spawning arena. Males behaved naturally both in terms of male–male interactions and attempts to achieve spawnings. Males having many, large breeding tubercles (i.e. rough skin) were significantly more often dominant in our dyadic trials than those with smooth skin. The dominant male in the trial exhibited a more active courtship behaviour than its subordinate rival. Papilloma skin disease did not affect the dominance rank. As a result of the relationship between skin roughness and male dominance, breeding tubercles may be used by the females as a cue for choosing a high-quality mate in a roach lek. Thus, breeding tubercles might offer a workable tool for examination of sexual selection among cyprinids.