Competition between Color Morphs of the Polychromatic Midas Cichlid Cichlasoma citrinellum

The Midas cichlid, Cichlasoma citrinellum, is a polychromatic fish that occurs in Nicaragua. All of these fish start life as normally colored, cryptic individuals. In some populations a few fish change into conspicuously colored morphs, most frequently gold. When kept in unmixed color groups, golds and normals grow at the same rate; but when they are mixed, growth of the golds becomes faster and that of the normals slower. Golds dominate normals in contests over food, which accounts for their advantage.