Cooperative signalling between opponents in fish fights.

Cichlids of the species Nannacara anomala employ several colour displays during fights which do not seem to signal either fighting ability or motivation. How should these colour displays be interpreted when winning is reliably predicted by weight asymmetries? Medial Line colour displays were associated with, and predicted, tail-beating, while Vertical Bar colour displays were associated with mouth-wrestling. I suggest that these colour displays are used to facilitate the transmission of assessment information within a fight, and that they are an example of cooperative signalling between opponents. The results support the idea that the structure of fights contains strong cooperative aspects.Copyright 1997 The Association for the Study of Animal Behaviour1997The Association for the Study of Animal Behaviour