July 10, 2025
July 10, 2025
Clayton D. Raines1,2, Cynthia R. Adams1,3, Morgan A. Biggs1, Vicki S. Blazer1, R. Scott Cornman4, Julianna J. Jett1,2, Pat M. Mazik2, Cheyenne R. Smith1,2, Heather L. Walsh1, Cassidy H. Shaw2,5, Luke R. Iwanowicz1,6
1U.S. Geological Survey, Eastern Ecological Science Center, Leetown Research Laboratory, Kearneysville, WV, 25430; 2West Virginia U.S. Geological Survey Cooperative Fish and Wildlife Research Unit, Morgantown, WV, 26505 3University of Pittsburgh, Department of Medicine, Pittsburg, PA, 15213; 4U.S. Geological Survey, Fort Collins Science Center, Fort Collins, CO 80526; 5Vermont Fish & Wildlife Department, Randolph Center, VT 05061; 6U.S. Department of Agriculture-Agricultural Research Service, National Center for Cool and Cold Water Aquaculture, Kearneysville, WV, 25430
The White Sucker (Catostomus commersonii) is an abundant North American fish known for its wide distribution, sexual dimorphism, and ecological importance as a sentinel species for environmental monitoring. This study investigates the detection and immune expression dynamics of White Sucker Hepatitis B Virus (WSHBV) and White Sucker Hepatitis C Virus (WhsuHV) in adult white suckers collected from the Sheboygan River, Wisconsin. During March 2016, two hundred fish were sampled and subjected to necropsies to document gross abnormalities and collect tissue for further analysis. Quantitative PCR (qPCR) and RT-qPCR assays were developed, yielding high efficiencies (96.39% for WSHBV, R²=0.987; 96.58% for WhsuHV, R²=0.989). Male fish showed higher virus prevalence and copy numbers than females, although statistical significance was not reached. While no overt liver pathology linked to viral infections was found, skin lesions were frequent in both virus-negative and infected individuals. Analysis of immune gene expression revealed significant sexual dimorphism, with males exhibiting more pronounced antiviral responses, particularly in cases of co-infection. These findings enhance our understanding of viral pathology and immune responses in white suckers, contributing valuable insights for effective fish health management strategies and environmental monitoring.
Cheyenne R. Smith1, Christopher A. Ottinger1, Megan K. Schall2, Kristina M. Gutchess3, Heather L. Walsh1, Geoffrey D. Smith4, Timothy A. Wertz5, Justin B. Greer6, Tyler Wagner7, Patricia M. Mazik8, and Vicki S. Blazer1
1United States Geological Survey, Eastern Ecological Science Center at Leetown Research Laboratory, 11649 Leetown Road, Kearneysville, WV 25430; 2Biological Sciences, Penn State Hazleton, 76 University Drive, Hazleton, Pennsylvania, USA; 3United States Geological Survey, New York Water Science Center, 425 Jordan Road, Troy, NY 12180; 4Pennsylvania Fish and Boat Commission, Division of Fisheries Management, Bellefonte, Pennsylvania, USA; 5Pennsylvania Department of Environmental Protection, Bureau of Clean Water, 400 Market Street, Harrisburg, PA 17101; 6United States Geological Survey, Western Fisheries Research Center, 6505 NE 65th Street, Seattle, Washington 98115; 7United States Geological Survey, Pennsylvania Cooperative Fish and Wildlife Research Unit, The Pennsylvania State University, University Park, Pennsylvania, USA; 8United States Geological Survey, West Virginia Cooperative Fish and Wildlife Research Unit, West Virginia University, 1145 Evansdale Drive, Morgantown, WV 26506
Smallmouth bass (Micropterus dolomieu), an economically important recreational sportfish, are vital indicators of ecosystem health because of their sensitivity to environmental disturbances. In the Potomac and Susquehanna rivers, concerns over pathogenic infections, mortality episodes, limited recruitment, and male endocrine disruption have historically reduced catch rates and prompted protective fishing regulations. Since 2013, a collaborative fish health monitoring effort in the Chesapeake Bay watershed has integrated land use analyses, water chemistry, plasma vitellogenin, histopathology, and gene expression to identify disease risk factors. To further understand resilience in wild smallmouth bass, immune function assays were incorporated from 2016 to 2018, including bactericidal and respiratory burst activities, lymphocyte mitogenesis, and the expression of over 100 contaminant- and immune-related genes. Advanced modeling integrating these immune responses with land use, water contaminants, and environmental factors revealed that host health status (as assessed by the health assessment index) had less influence on immune suppression than chemical mixtures and climatic factors, including flow, season, and drought severity. Notably, the interaction between high river flow and metolachlor concentrations was predicted to suppress background immune responses significantly below the mean on a log scale, suggesting a compounded negative effect. These results underscore that cells already engaged in defense may have limited capacity to respond to new stressors, increasing disease vulnerability. By emphasizing immune responses as mechanistic indicators, this study highlights critical interactions between chemical exposures and environmental conditions affecting fish health. Ongoing research is expanding these insights through laboratory exposures, refined modeling approaches, and the development of nonlethal immune monitoring techniques to support conservation and management of smallmouth bass populations.
Adrian Deil Manliclic1, Megan Shavalier1, Rachel Leads1, Katie King1, Thomas Loch1, Cheryl Murphy1
1Department of Fisheries and Wildlife, Michigan State University, East Lansing MI
Perfluorooctane sulfonate (PFOS) is among the most widespread per- and polyfluoroalkyl substances, with frequent detection across various environmental media, including water and fish samples from rivers, lakes, and streams throughout North America. Although the environmental and health risks of PFOS are increasingly recognized, its specific effects on wildlife, particularly fish, remain poorly understood. In particular, its impact on disease susceptibility and survival in fish has received limited investigation. Given the high concentrations of PFOS detected in fish populations across the Great Lakes region, evaluating these effects is essential. In this study, juvenile lake trout (Salvelinus namaycush), were exposed to PFOS via water immersion using a flow-through system for 96 hours. Following exposure, fish were challenged against Epizootic Epitheliotropic Disease virus challenges via static immersion, using established disease challenge protocols. Post-challenge, all fish were transferred to clean flow-through systems for observation and monitoring of disease progression and survival. Tissue samples were collected at defined intervals for histopathology and quantitative PCR to confirm pathogen presence and quantify viral load. This study aims to elucidate the role of PFOS in modulating host–pathogen interactions in fish, with significant implications for aquatic animal health, environmental management, and conservation. If PFOS impairs the immune function of this keystone species, targeted remediation within affected watersheds will be crucial to protect biodiversity and ensure long-term ecosystem sustainability.