The gene involved in the origin of melanism in rock pocket mice is.
As a reaction and antidote to white racism, melanism is understandable.
All that would be necessary at the fish market is to pick one scale from each flounder having melanism on the blind side.
British Dictionary definitions for melanism
the condition in man and animals of having dark-coloured or black skin, feathers, etc. Industrial melanism is the occurrence of dark varieties of animals, esp moths, in smoke-blackened industrial regions, in which they are well camouflaged