Assessment of skin and liver neoplasms in brown bullhead (Ameiurus nebulosus) collected at the Ashtabula River Area of Concern and associated reference site, Ohio, in 2016

Brown bullhead (Ameiurus nebulosus) is a commonly used indicator species for tumor surveys at Great Lakes Areas of Concern. The “fish tumors or other deformities” is one of the beneficial use impairments at the Ashtabula River Area of Concern. In May 2016, 150 brown bullhead were collected in the lower Ashtabula River and 150 were collected in the nearby Conneaut Creek as a reference. Length, weight and external visible abnormalities were documented. Fish were euthanized, and skin lesions and liver tissue preserved for histopathological analyses. Otoliths were collected for age analyses. The percentage of bullhead with raised external lesions on lips, barbels and body surface was 34.7 percent at the Ashtabula River and 23.3 percent at Conneaut Creek. At the Ashtabula River, 26.7 percent of the bullhead collected had skin neoplasms, including papillomas, melanomas and squamous cell carcinomas, whereas at Conneaut Creek 18.6 percent had only papillomas, benign skin tumors. Liver neoplasms were observed in 7.3 percent of the bullhead from the Ashtabula River and 4.7 percent of those from Conneaut Creek. These neoplasms were observed in fish 6 years of age or older at both sites.