In addition, Xmrk males (regardless of Sc phenotype) were more aggressive than Xmrk‐deficient (wild‐type) males [48] and collections of males from four natural populations of these fish found that those with malignant melanomas were significantly larger than both Xmrk males without melanomas and Xmrk‐deficient males [49]. The gene discussed is ERMAP; the disease is melanoma.