Melanistic skin lesions in Smallmouth Bass from the Susquehanna River and Great Lakes tributaries

Session: Disease and Mortality in Fishes

Vicki Blazer, U.S. Geological Survey, vblazer@usgs.gov
Kelsey Young, University of Georgia, ky47744@uga.edu
Geoffrey Smith, Pennsylvania Fish and Boat Comission, geofsmith@pa.gov
Adam Sperry, U.S. Geological Survey, National Fish Health Research Laboraotry, asperry@usgs.gov
Luke Iwanowicz, U.S. Geological Survey, liwanowicz@usgs.gov

Abstract

Visible skin abnormalities, including erosions and tumors have been used worldwide as indicators of ecosystem health. Recently, hyperpigmented or melanistic areas of skin, referred to in the popular press and social media as the “blotchy bass” syndrome have raised concerns among the fishing public and resource managers. There is a perception that the incidence of this condition is increasing and may be a result of degraded environmental conditions. From 2012 to 2017 the prevalence of the condition was assessed at eight sites along the mainstem Susquehanna and nine sites along the Juniata River. The prevalence was also documented in fish health monitoring and assessment studies in bass from Great Lakes and Susquehanna tributaries (2010-2018). During these assessments pieces of melanistic lesions were collected for microscopic pathology and pieces of normal and melanistic skin preserved for molecular analyses. Transcriptome analyses were conducted on six normal and six melanistic pieces of skin. Differentially expressed genes were identified between the two groups. From this analyses a custom codeset of 62 genes was developed and 34 normal and melanistic skin samples were analyzed using Nanostring nCounter technology for assessing gene expression. Prevalence, microscopic pathology and gene expression data will be presented.