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 the immediate and upstream catchments with 2016 land cover data. Correlations between biological variables and transcripts were made in addition to differences between sites. The results showed that males had biological variables that correlated with transcripts associated with endocrine disruption and a high rate of testicular oocytes and plasma vitellogenin (biomarkers of estrogenic contaminant exposure).

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 Potomac, Susquehanna and James. Fish were collected by boat electroshocking, euthanized in the field, weighed, measured, a blood samples collected and a necropsy completed that included documenting any visible abnormalities and collecting tissues for histopathology. Plasma obtained from blood samples was analyzed for vitellogenin, a yolk precursor widely used as an indicator of estrogenic exposure in immature and male fishes. Five to seven sections of testes were processed for microscopic analyses, embedded in paraffin, sectioned at 5 µm, stained with hematoxylin and eosin. The presence of testicular oocytes was noted and the severity rated from 1 to 4 based on number and arrangement of oocytes.

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 Potomac, Susquehanna and James. Fish were collected by boat electroshocking, euthanized in the field, weighed, measured, a blood samples collected and a necropsy completed that included documenting any visible abnormalities and collecting tissues for histopathology. Plasma obtained from blood samples was analyzed for vitellogenin, a yolk precursor widely used as an indicator of estrogenic exposure in immature and male fishes. Five to seven sections of testes were processed for microscopic analyses, embedded in paraffin, sectioned at 5 µm, stained with hematoxylin and eosin. The presence of testicular oocytes was noted and the severity rated from 1 to 4 based on number and arrangement of oocytes.

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 was conducted from 2013-2019 to identify temporal changes associated with SMB reproductive health. Grab surface water samples were collected and analyzed for over 300 organic contaminants, including pesticides, phytoestrogens, pharmaceuticals, hormones and total estrogenicity (E2Eq). Adult SMB were collected and sampled for multiple endpoints, including gene transcripts associated with reproduction (molecular), histopathology (cellular), and organosomatic indices (tissue). In males, biomarkers of estrogenic endocrine disruption, including testicular oocytes (TO) and plasma vitellogenin (Vtg) were assessed. The results identified numerous agriculture-related contaminants or land use associated with gene transcripts in males and females and a positive association of pesticides in the immediate catchment with TO severity and E2Eq with plasma Vtg in males. Prevalence of TO and detectable levels of plasma Vtg, liver vitellogenin transcripts (vtg) and testis vtg were high throughout the study. Peaks of complex mixtures of numerous contaminants occurred during the spring/early summer when early development occurs and to a lesser extent in fall/winter during recrudescence. Management practices to reduce exposure during these critical and sensitive periods may enhance reproductive health of economically important sportfishes.

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 was conducted from 2013-2019 to identify temporal changes associated with SMB reproductive health. Grab surface water samples were collected and analyzed for over 300 organic contaminants, including pesticides, phytoestrogens, pharmaceuticals, hormones and total estrogenicity (E2Eq). Adult SMB were collected and sampled for multiple endpoints, including gene transcripts associated with reproduction (molecular), histopathology (cellular), and organosomatic indices (tissue). In males, biomarkers of estrogenic endocrine disruption, including testicular oocytes (TO) and plasma vitellogenin (Vtg) were assessed. The results identified numerous agriculture-related contaminants or land use associated with gene transcripts in males and females and a positive association of pesticides in the immediate catchment with TO severity and E2Eq with plasma Vtg in males. Prevalence of TO and detectable levels of plasma Vtg, liver vitellogenin transcripts (vtg) and testis vtg were high throughout the study. Peaks of complex mixtures of numerous contaminants occurred during the spring/early summer when early development occurs and to a lesser extent in fall/winter during recrudescence. Management practices to reduce exposure during these critical and sensitive periods may enhance reproductive health of economically important sportfishes.

Adult and young of the year smallmouth bass from the Chesapeake Bay watershed have faced health issues (mortality events, disease by a variety of pathogens, endocrine disruption in male fish, evidence of oxidative damage to tissues, and signs of exposure to chemical contaminants) at multiple sites within the Susquehanna and Potomac River basins. Functional immune assays were added to long-term comprehensive monitoring assessments to determine if immunosuppression was playing a role in observed disease and mortalities because no one single or consistent cause could be identified. The functional immune assays measured bactericidal activity, respiratory burst activity, and lymphocyte mitogenesis using leukocytes isolated from anterior kidney tissue. From 2016-2021, a total of 740 smallmouth bass were sampled among eight (8) sites. Twenty adults were sampled from each site in spring (pre-spawn; April – May) and fall (recrudescence; October – November) at different points in the study. Ancillary data, including biometrics of the fish and parasite/macrophage aggregate counts in multiple tissue types, were collected in conjunction with the immune data. The functional immune assays serve as part of an integrated assessment to determine environmental stressors and infectious agents that may modulate the immune response in wild smallmouth bass, ultimately making them more susceptible to disease and death. Therefore, it is important to consider the functional immune data alongside other aspects of host and environmental health.

Adult and young of the year smallmouth bass from the Chesapeake Bay watershed have faced health issues (mortality events, disease by a variety of pathogens, endocrine disruption in male fish, evidence of oxidative damage to tissues, and signs of exposure to chemical contaminants) at multiple sites within the Susquehanna and Potomac River basins. Functional immune assays were added to long-term comprehensive monitoring assessments to determine if immunosuppression was playing a role in observed disease and mortalities because no one single or consistent cause could be identified. The functional immune assays measured bactericidal activity, respiratory burst activity, and lymphocyte mitogenesis using leukocytes isolated from anterior kidney tissue. From 2016-2021, a total of 740 smallmouth bass were sampled among eight (8) sites. Twenty adults were sampled from each site in spring (pre-spawn; April – May) and fall (recrudescence; October – November) at different points in the study. Ancillary data, including biometrics of the fish and parasite/macrophage aggregate counts in multiple tissue types, were collected in conjunction with the immune data. The functional immune assays serve as part of an integrated assessment to determine environmental stressors and infectious agents that may modulate the immune response in wild smallmouth bass, ultimately making them more susceptible to disease and death. Therefore, it is important to consider the functional immune data alongside other aspects of host and environmental health.

Monitoring wild fish health and associated exposure effects in regions where agriculture and development have impacted rivers and streams has become a valuable research tool. Smallmouth bass (Micropterus dolomieu) are a sensitive, indicator species that exhibit symptoms of immunosupression and endocrine disruption in response to water quality changes and contaminant exposure. In the Susquehanna River drainage, smallmouth bass have been used in biomonitoring assessments to help understand changes in the population due to poor young-of-the-year recruitment and health effects. To help determine effects of agriculture and development on smallmouth bass health, two sites (a developed/agriculture site and a forested site) were selected where bass and water chemistry were sampled from 2015-2019. Bass were sampled for histopathology to assess parasite and macrophage aggregate density in the liver and spleen, condition factor (Ktl), hepatic gene transcripts (immune function, oxidative stress, cell proliferation, stress, and contaminant, thyroid, and insulin/pancreas metabolism), hepatosomatic index (HSI), and a health assessment index (HAI). Land use at the developed/agricultural site included greater pesticide application rates and % high phytoestrogen crop cover and there were more detections and higher concentrations of pesticides, wastewater-associated contaminants, hormones, phytoestrogens, and mycotoxins than at the forested site. Additionally at this site, oxidative stress, lipid metabolism, and thyroid-related hepatic gene transcripts were associated with contaminants/land use applications; whereas at the forested site there were far fewer associations. At both sites, there were multiple associations of contaminants/land use applications with biological variables (HSI, Ktl, and liver and spleen macrophage aggregate density), which may indicate that changes at the molecular level may be a better indicator of exposure effects unique to each site. This work will help to understand the importance of timing for land management practices, how contaminants change temporally, and that agricultural practices affect hepatic gene transcripts associated with immune function and disease resistance and may negatively affect the health of smallmouth bass.

Monitoring wild fish health and associated exposure effects in regions where agriculture and development have impacted rivers and streams has become a valuable research tool. Smallmouth bass (Micropterus dolomieu) are a sensitive, indicator species that exhibit symptoms of immunosupression and endocrine disruption in response to water quality changes and contaminant exposure. In the Susquehanna River drainage, smallmouth bass have been used in biomonitoring assessments to help understand changes in the population due to poor young-of-the-year recruitment and health effects. To help determine effects of agriculture and development on smallmouth bass health, two sites (a developed/agriculture site and a forested site) were selected where bass and water chemistry were sampled from 2015-2019. Bass were sampled for histopathology to assess parasite and macrophage aggregate density in the liver and spleen, condition factor (Ktl), hepatic gene transcripts (immune function, oxidative stress, cell proliferation, stress, and contaminant, thyroid, and insulin/pancreas metabolism), hepatosomatic index (HSI), and a health assessment index (HAI). Land use at the developed/agricultural site included greater pesticide application rates and % high phytoestrogen crop cover and there were more detections and higher concentrations of pesticides, wastewater-associated contaminants, hormones, phytoestrogens, and mycotoxins than at the forested site. Additionally at this site, oxidative stress, lipid metabolism, and thyroid-related hepatic gene transcripts were associated with contaminants/land use applications; whereas at the forested site there were far fewer associations. At both sites, there were multiple associations of contaminants/land use applications with biological variables (HSI, Ktl, and liver and spleen macrophage aggregate density), which may indicate that changes at the molecular level may be a better indicator of exposure effects unique to each site. This work will help to understand the importance of timing for land management practices, how contaminants change temporally, and that agricultural practices affect hepatic gene transcripts associated with immune function and disease resistance and may negatively affect the health of smallmouth bass.

Field data of age-0 smallmouth bass (Micropterus dolomieu) estimated age, lengths and weights, distribution from field sampling, and results from environmental DNA surveys from the Yellowstone River in Montana. Data were used in conjunction with existing stream temperature data from USGS gages to evaluate if temperature is related to age-0 size at the onset of winter.