Definition: Nuchal hump is a hump of tissue on the head, usually above the eyes, seen in some spawning or fast-current fish. It is sometimes referred to as a Kok. In certain species of cichlid, the hump will develop as a mature male ages, and is considered a highly desirable trait in some show fish. Even mature freshwater Angelfish, which are a cichlid species, will sometimes develop a nuchal hump.