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Heather Walsh

Dr. Heather Walsh is a Research Fish Biologist that has been involved in research at the Eastern Ecological Science Center since 2006. 

Dr. Walsh has focused on developing molecular techniques to better understand mechanisms associated with disease in wild fish. To serve this purpose, she has developed her skills in histopathology, in situ hybridization techniques, and laser capture microdissection. The use of these techniques has helped to understand disease observed during fish health assessments conducted in the Great Lakes and Chesapeake Bay (including the Susquehanna and Potomac River drainage). Much of her work has focused on fish species used as indicators of environmental contamination, including smallmouth bass, brown bullhead catfish, white suckers, and yellow perch. She also uses PCR, Sanger sequencing, Nanostring technology, and RNA-Seq to help identify parasites or pathogens, for transcript abundance analyses, and de novo transcriptome development. 

Professional Experience

  • B.S., Environmental Studies with a Concentration in Aquatic Science, Shepherd University, Shepherdstown, WV, 2008

  • B.S., Environmental Studies with a Concentration in Aquatic Science, Shepherd University, Shepherdstown, WV, 2008

  • M.S., Wildlife and Fisheries Management, West Virginia University, Morgantown, WV, 2011

  • Ph.D., Forest Resource Science Program, Wildlife and Fisheries Management Major, West Virginia University, 2018

Affiliations and Memberships*

  • American Fisheries Society, Fish Health Section

  • Northeast Fish Health Committee 

Science and Products

Water Chemistry and Smallmouth Bass Biological Data From the Potomac River, Dargan, Maryland, 2013-2019

Decades of poor reproductive success and young-of-the-year recruitment, in addition to adult mortality, has led to a decline in the smallmouth bass (SMB) population in subwatersheds of the Potomac River. Previous studies have identified numerous biologic and environmental stressors associated with negative effects on SMB health. To better understand the impact of these stressors, the current study
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Chesapeake Bay Activities, Eastern Ecological Science Center

Biological variables and liver and testes transcript abundance from smallmouth bass sampled in the Lake Erie drainage, Pennsylvania (2016)

In 2016, smallmouth bass were collected from three sites in the Lake Erie drainage in Erie County, Pennsylvania and an out-of-basin site in the Allegheny River drainage in order to assess reproductive health and identify endocrine disruption responses. Pieces of liver and gonad were taken in Z-Fix and RNALater for histology and transcript abundance analysis. A landscape analysis was conducted for
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Ecosystems, Contaminant Biology, Environmental Health Program, Toxic Substances Hydrology, Eastern Ecological Science Center

Presence/Absence of Myxobolus inornatus, Aeromonas spp., and Flavobacterium spp. in Young-of-the-Year Smallmouth Bass with Fluorescence In Situ Hybridization

Histopathological assessments of young-of-the-year smallmouth bass (YOY SMB) in the Susquehanna River drainage identified a high prevalence of the myxozoan Myxobolus inornatus. This myxozoan infects the connective tissue of the muscle below the skin but is sometimes observed in the esophagus and buccal cavity. In some instances, shallow infections cause breaks in the skin which could increase the
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Ecosystems, Contaminant Biology, Environmental Health Program, Toxic Substances Hydrology, Eastern Ecological Science Center

Morphometric, Age, Visible Abnormalities, Skin and Liver Neoplasms, and Stable Isotopes in White Sucker Collected in the St. Louis River and Estuary, Minnesota/Wisconsin, 2011-2015

The dataset provides length, weight, age, observations of visible external abnormalities, liver and skin histopathology and stable isotopes of white sucker captured within the St. Louis river and associated bays.
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Ecosystems, Contaminant Biology, Environmental Health Program, Toxic Substances Hydrology, Eastern Ecological Science Center

Morphometric, Age and Concentrations of Perfluoroalkyl Substances in Smallmouth Bass Plasma from Four Sites in the Chesapeake Bay Watershed

Archived plasma from fish health monitoring sites within the Chesapeake Bay watershed was analyzed for 13 perfluoroalkyl compounds. Smallmouth bass were collected from two sites in the Potomac River drainage (Antietam Creek, Maryland and South Branch Potomac, West Virginia) and two in the Susquehanna River drainage (West Branch Mahantango Creek, Pennsylvania and Pine Creek, Pennsylvania). Site and
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Ecosystems, Contaminant Biology, Environmental Health Program, Toxic Substances Hydrology, Chesapeake Bay Activities, Eastern Ecological Science Center

2004-2010 Chesapeake Bay Smallmouth and Largemouth Bass Estrogenic Biomarker Data

The data was gathered to document the extent and severity of biomarkers of exposure to estrogenic chemicals in smallmouth and largemouth bass. Samples were collected from 2004 through 2010 at sites in five watersheds within the Chesapeake Bay watershed. A total of 281 largemouth bass were collected from the Potomac, Susquehanna, Patuxent and Rappahannock rivers and 1,384 smallmouth bass from the P
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Ecosystems, Contaminant Biology, Chesapeake Bay Activities, Eastern Ecological Science Center

Abundance of 50 transcripts from microdissected liver samples of smallmouth bass

There is an increasing emphasis on effects-based monitoring to document responses associated with exposure to complex mixtures of chemicals, climate change, pathogens, parasites and other environmental stressors in fish populations. For decades aquatic monitoring programs have included the collection of tissues preserved for microscopic pathology. Consequently, formalin-fixed, paraffin-embedded (F
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Eastern Ecological Science Center
Sunrise of blue and orange hues and clouds illuminated by the rising sun. Clear water reflects the sky and the leafless tree
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Scientist inserting a needle with a syringe in the caudal vein (located below the spine) of a smallmouth bass
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Scientist examining the gills of a smallmouth bass for abnormalities such as parasites, erosion, and fraying.
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The Leetown trout pond on a beautiful, sunny day with blue skies and green foliage all around.
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Chesapeake Bay Land Use Map and Chart
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Chart of changes in smallmouth bass
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Chart of concentrations of three of the most detected pesticides in Dargan, MD
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Photo of a 45" muskellunge used in a catch and release study on angling mortality during warmer summer conditions.
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Histology laboratory (prior to renovations) with coverslipping area, file/record keeping center, and embedding center.
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Scientists working with a fish specimen to assess health and disease in the fish population.
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Filter Total Items: 29

A case study: Temporal trends of environmental stressors and reproductive health of smallmouth bass (Micropterus dolomieu) from a site in the Potomac River Watershed, Maryland, USA

Decades of poor reproductive success and young-of-the-year survival, combined with adult mortality events, have led to a decline in the smallmouth bass (SMB; Micropterus dolomieu) population in sections of the Potomac River. Previous studies have identified numerous biologic and environmental stressors associated with negative effects on SMB health. To better understand the impact of these stresso
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Chesapeake Bay Activities, Eastern Ecological Science Center

Potential health effects of contaminant mixtures from point and nonpoint sources on fish and frogs in the New Jersey Pinelands

Aquatic ecosystems convey complex contaminant mixtures from anthropogenic pollution on a global scale. Point (e.g., municipal wastewater) and nonpoint sources (e.g., stormwater runoff) are both drivers of contaminant mixtures in aquatic habitats. The objectives of this study were to identify the contaminant mixtures present in surface waters impacted by both point and nonpoint sources, to determin
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Water Resources, California Water Science Center, New Jersey Water Science Center, South Atlantic Water Science Center (SAWSC)

Reproductive health and endocrine disruption in smallmouth bass (Micropterus dolomieu) from the Lake Erie drainage, Pennsylvania, USA

Smallmouth bass Micropterus dolomieu were sampled from three sites within the Lake Erie drainage (Elk Creek, Twentymile Creek, and Misery Bay, an embayment in Presque Isle Bay). Plasma, tissues for histopathological analyses, and liver and testes preserved in RNALater® were sampled from 30 smallmouth bass (of both sexes) at each site. Liver and testes samples were analyzed for transcript abundance
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Ecosystems, Contaminant Biology, Environmental Health Program, Toxic Substances Hydrology, Eastern Ecological Science Center

Development of a multiplex fluorescence in situ hybridization assay to identify coinfections in young-of-the-year smallmouth bass

Histopathological assessments of young-of-the-year (age-0) Smallmouth Bass Micropterus dolomieu in the Susquehanna River drainage identified a high prevalence of the myxozoan Myxobolus inornatus. This myxozoan infects the connective tissue of the muscle below the skin but is sometimes observed in the esophagus and buccal cavity. In some instances, shallow infections cause breaks in the skin, which
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Ecosystems, Contaminant Biology, Environmental Health Program, Toxic Substances Hydrology

Identification of Aphanomyces invadans, the cause of epizootic ulcerative syndrome, in smallmouth bass (Micropterus dolomieu) from the Cheat River, West Virginia, USA

The oomycete Aphanomyces invadans (Saprolegniales, Oomycetes), the cause of epizootic ulcerative syndrome (EUS), is an OIE (World Organization for Animal Health) reportable pathogen, capable of infecting many fish species worldwide in both freshwater and estuarine environments (Iberahim et al. 2018). Since the discovery of EUS in Japan in 1971 (Egusa and Masuda 1971), it has spread globally and ca
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Ecosystems, Contaminant Biology, Environmental Health Program, Toxic Substances Hydrology

Perfluoroalkyl substances in plasma of smallmouth bass from the Chesapeake Bay Watershed

Smallmouth bass Micropterus dolomieu is an economically important sportfish and within the Chesapeake Bay watershed has experienced a high prevalence of external lesions, infectious disease, mortality events, reproductive endocrine disruption and population declines. To date, no clear or consistent associations with contaminants measured in fish tissue or surface water have been found. Therefore,
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Ecosystems, Contaminant Biology, Environmental Health Program, Toxic Substances Hydrology, Chesapeake Bay Activities, Pennsylvania Water Science Center

Assessing native fish restoration potential in Catoctin Mountain Park

Biological conservation is a fundamental purpose of the National Park system, and Catoctin Mountain Park (CATO) supports high-quality habitat for native fishes in the headwaters of the Chesapeake Bay watershed in eastern North America. However, native Blue Ridge sculpin (Cottus caeruleomentum) have been extirpated in Big Hunting Creek above Cunningham Falls in CATO. Prior research indicates that i
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Chesapeake Bay Activities

Retrospective analysis of estrogenic endocrine disruption and land-use influences in the Chesapeake Bay watershed

The Chesapeake Bay is the largest estuary in the United States and its watershed includes river drainages in six states and the District of Columbia. Sportfishing is of major economic interest, however, the rivers within the watershed provide numerous other ecological, recreational, cultural and economic benefits, as well as serving as a drinking water source for millions of people. Consequently,
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Ecosystems, Water Resources, Contaminant Biology, Environmental Health Program, Toxic Substances Hydrology, Chesapeake Bay Activities, Eastern Ecological Science Center, New Jersey Water Science Center

Development of a suite of functional immune assays and initial assessment of their utility in wild smallmouth bass health assessments

Methods were developed for measuring immune function in Micropterus dolomieu (smallmouth bass). The ultimate objective is to monitor and evaluate changes over time in immune status and disease resistance in conjunction with other characteristics of fish health and environmental stressors. To test these methods for utility in ecotoxicological studies, 192 smallmouth bass, age 2 years and older, wer
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Ecosystems, Eastern Ecological Science Center, Chesapeake Bay Activities, Pennsylvania Water Science Center

The effects of tissue fixation on sequencing and transcript abundance of nucleic acids from microdissected liver samples of smallmouth bass (Micropterus dolomieu)

There is an increasing emphasis on effects-based monitoring to document responses associated with exposure to complex mixtures of chemicals, climate change, pathogens, parasites and other environmental stressors in fish populations. For decades aquatic monitoring programs have included the collection of tissues preserved for microscopic pathology. Consequently, formalin-fixed, paraffin-embedded
By
Ecosystems, Eastern Ecological Science Center

A fishery after the decline: The Susquehanna River Smallmouth Bass story

The Smallmouth Bass Micropterus dolomieu fishery in the Susquehanna River basin, Pennsylvania, is one of the most socioeconomically important fisheries in the region and has recently undergone considerable changes. These changes started in 2005, when disease was documented in young-of-the-year (age-0) Smallmouth Bass. Shortly thereafter, declines in abundance of both juveniles and adults were obse
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Ecosystems, Cooperative Research Units, Chesapeake Bay Activities, Eastern Ecological Science Center

Assessment of microscopic pathology in fishes collected at sites impacted by wood tar in Pennsylvania

In an effort to determine whether fish populations in an area affected by wood tar waste exhibited health effects, fish were collected and analyzed with histopathology. Multiple species, including Mottled Sculpin (Cottus bairdii), Creek Chub (Semotilus atromaculatus), White Sucker (Catostumus commersonii), Redside Dace (Clinostomus elongatus), Common Shiner (Luxilus cornutus), and Western Blacknos
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Ecosystems, Eastern Ecological Science Center, Pennsylvania Water Science Center
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Collecting water quality samples from the New River Gorge

A case study of temporal trends in risk factors associated with endocrine disruption in smallmouth bass

Issue The USGS has a long-term research effort that identified endocrine disruption in smallmouth bass (SMB) in the Chesapeake Bay watershed. Endocrine disruption can cause many changes in fish, including intersex characteristics where fish develop characteristics of the other sex, such as immature eggs forming in males. An overview by USGS of endocrine disruption in fish found the condition...
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Environmental Health Program, Fish & Wildlife Disease, Chesapeake Bay Activities, Eastern Ecological Science Center
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A case study of temporal trends in risk factors associated with endocrine disruption in smallmouth bass

Issue The USGS has a long-term research effort that identified endocrine disruption in smallmouth bass (SMB) in the Chesapeake Bay watershed. Endocrine disruption can cause many changes in fish, including intersex characteristics where fish develop characteristics of the other sex, such as immature eggs forming in males. An overview by USGS of endocrine disruption in fish found the condition...
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Science and Products

*Disclaimer: Listing outside positions with professional scientific organizations on this Staff Profile are for informational purposes only and do not constitute an endorsement of those professional scientific organizations or their activities by the USGS, Department of the Interior, or U.S. Government