Abstract
The Mediterranean cabrilla sea bass Serranus cabrilla exhibits two colour morphs (red and yellow) that appear to be depth segregated, with yellow individuals found below 20 m and red ones found above 20 m. Morphology and otolith analyses show that yellow fish are larger and older. There were similar allelic frequencies between colour morphs, but significant differences in the genotypic frequencies with an increase of excess of heterozygotes in yellow specimens. It is proposed that the yellow fish are older and develop from younger red fish that have migrated to deeper water.