Colour and pattern in relation to sexual and aggressive behaviour in the bluehead wrasse Thalassoma bifasciatum.

Terminal phase adult male bluehead wrasse show rapid and frequent changes of body colour from bright green to opalescent. Green body colour is associated with aggressive chases of other fish, opalescent with courting females and spawning and so the body colour gives an indication of the fish's 'intention' over the next few seconds. Pectoral fin spots appear during courtship and a hypothesis is suggested for their function.