USGS Use of Comprehensive Fish Health Assessments Invasive Catfish Chesapeake Bay Drainage

* Applications will be reviewed on a rolling-basis.

USGS Office/Lab and

Location:

A research opportunity is currently available with the U.S. Geological Survey (USGS) located in Kearneysville, West Virginia.

The USGS mission is to monitor, analyze, and predict current and evolving dynamics of complex human and natural Earth-system interactions and to deliver actionable intelligence at scales and time frames relevant to decision makers. As the Nation's largest water, earth, and biological science and civilian mapping agency, USGS collects, monitors, analyzes, and provides science about natural resource conditions, issues, and problems.

Research Project: Many types of environmental contaminants, individually and in combination, have become ecological and human health concerns. In the Chesapeake Bay drainage, elevated contaminant concentrations in fish can affect recreational, subsistence, and commercial fisheries by creating fish consumption concerns. In recent years, there has also been increased interest in promoting consumption of invasive blue catfish (Ictalurus furcatus), including within state institutions such as hospitals, correctional facilities, and schools.

Although mercury and per- and polyfluoroalkyl substances (PFAS) have been measured in fish from select Maryland locations, other contaminants capable of accumulating in blue catfish remain understudied.

This research will use previously collected blue catfish from multiple Chesapeake Bay tributaries to evaluate relationships between contaminant concentrations and fish health endpoints, including visual examinations, morphometrics, histopathology, and gene expression. Plasma will be analyzed for PFAS, and muscle tissue will be analyzed for microplastics, polychlorinated biphenyls (PCBs), 6

PPD-quinone (6

PPD-Q), and heavy metals. You will receive training in RNA extraction and quality assessment, preparation and evaluation of samples for RNA sequencing, and bioinformatic analysis of transcriptomic data. You will also learn to integrate transcriptomic results with contaminant concentrations and fish health data to evaluate biological responses associated with contaminant exposure.

A complementary component will focus on invasive flathead catfish (Pylodictis olivaris). Flathead catfish are highly prized by some recreational and subsistence anglers, and their large body size has contributed to unauthorized introductions into new waterways for trophy fisheries. Such movement creates questions regarding contaminants and pathogens that may occur in these fish and potentially accompany introductions into additional aquatic systems. Despite these concerns, contaminant concentrations and health endpoints in flathead catfish remain understudied within the Chesapeake Bay drainage.

Flathead catfish will be sampled from approximately three to four locations within the Chesapeake Bay drainage during spring 2027. Fish will undergo comprehensive health assessments comparable to those conducted for blue catfish, and samples will be evaluated for heavy metals, PFAS, PCBs, 6

PPD-Q, microplastics, and selected pathogens. You will receive training in field-based fish health assessments, including fish necropsy, blood and tissue collection, tissue preservation and skin swabs for molecular analyses, morphometric measurements, and identification of gross abnormalities. Laboratory experiences will include molecular techniques, histological methods, and histopathological assessment. Sampling will occur collaboratively, providing experience with team-based research and opportunities to interact with scientists and research partners.

The overarching goal is to improve understanding of contaminant exposure and associated biological responses in invasive catfish within the Chesapeake Bay drainage. The blue catfish component will evaluate associations among contaminant concentrations, transcriptomic responses, histopathology, morphometrics, and other indicators of fish health. RNA-sequencing and bioinformatic approaches will be used to identify molecular responses associated with contaminant exposure and observed health effects.

The flathead catfish component will characterize contaminant burdens, pathogen occurrence, and fish health endpoints at multiple locations. Comparable assessments across blue and flathead catfish will allow similarities and differences between these invasive species to be examined. Collectively, the research will address data gaps relevant to environmental contaminants,…