Predicting and assessing dominance from size and coloration in the polychromatic midas cichlid

To test whether gold morphs dominate normal ones, twelve groups were observed, each consisting of three golds and three normals paired by weight. Golds dominated comparable normals. Smaller golds also profited from sharing the colour of the dominant fish. Contest and approach declined across days, but attack and yield remained high. Standard deviation of rank was progressively greater with higher rank, but uncertainty of rank plotted as an inverted U. Behaviours important in dominance showed high dependence on type of fish but low dependence on day; these behaviours also had more variation attributable to the coloration factor. From a set of stated criteria, dominance is deemed best assessed here by an index: (attacks) ?o (yields + attacks); contesting (threat) is actually misleading.