Chromatoblastomas and related pigmented lesions in deepwater redfish, Sebastes mentella (Travin), from North Atlantic areas, especially the Irminger Sea

Abstract This study involved 34 960 specimens of deepwater redfish, Sebastes mentella (Travin), from the North Atlantic, 21 460 of them from the Irminger Sea. One hundred and three specimens of this species, 96 with pigmented lesions, were examined histologically. The black patches on the redfish skin proved to be superficial melanosis (48 cases) and deep melanosis (24 cases). Skin pterinophorosis was noted in 20 cases. Pigment tissue neoplasms were observed in 26 fish; all were benign chromatoblastomas. Fourteen tumours were diagnosed as melanomas originating from melanophores, seven as pterinophoromas originating from pterinophores, and five as pterino-melanophoromas or melano-pterinophoromas of mixed origin of both chromatophore types. The tumours on the trunk of redfish occurred only in pigmented areas larger than 20 cm². Fish with such areas constitute no more than 2.4% of the total Irminger Sea redfish population. Most (76.2%) of pigmented lesions in this redfish population did not exceed 5 cm² in area. The arrangement of pigmented areas differed in males and females. In females, 97% of patches were found between the pectoral and the first dorsal fins, whilst in males, 84% of patches were situated on the head and caudal fin. Pigmented lesions occurred 2–5 times more often in females than males. The causes of pigment tissue neoplasms and pigmented lesions in deepwater redfish are unknown.