Physiological and molecular endpoints observed in juvenile largemouth bass in response to an estrogen (17α-ethinylestradiol) and subsequently a bacterial challenge (Edwardsiella piscicida) exposure under laboratory conditions. Also included are water quality and chemical concentration data.

Physiological and molecular endpoints observed in juvenile largemouth bass in response to an estrogen (17α-ethinylestradiol) and subsequently a bacterial challenge (Edwardsiella piscicida) exposure under laboratory conditions. Also included are water quality and chemical concentration data.

Largemouth base histological development and transcriptomic changes in gonad tissue after early life stage exposure to Atrazine (1-Chloro-3-ethylamino-5-isopropylamino-2,4,6-triazine) or the model estrogen 17α-ethinylestradiol.

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).

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).

Adult largemouth bass have been shown to be sensitive to induction of intersex in response to chronic estrogen exposures over a complete reproductive cycle. Late summer to fall is the period of early gonad recrudescence when spermatogenesis is beginning in preparation for the spawning season in the spring. Our objective was to assess in 2018 whether early gonad recrudescence was a period of sensitivity for induction of intersex and/or alterations in reproductive condition or function. Adult male largemouth bass were exposed in outdoor pond mesocosms from post-spawning to early gonad recrudescence to either 17alpha-ethinylestradiol or to a mixture of endocrine-active substances commonly detected in the Chesapeake Bay watershed (atrazine and estrone). Gonad samples were sent overnight to Wetland and Aquatic Research Center laboratories and sperm motility was measured by computer assisted sperm motion analysis. Overall, male reproductive condition, sperm count, and sperm motility were analyzed.

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.

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.

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.

Disease outbreaks, skin lesions, fish kill events, and reproductive abnormalities have been observed in wild populations of bass in the Chesapeake Bay watershed. Occurrence of synthetic and natural hormones from wastewater treatment plants and livestock operations, pesticides from agricultural lands, and phytoestrogens from cover crops have been implicated as potential causes of these adverse effects. Late summer to fall is the period of early gonad recrudescence in adult bass when spermatogenesis and oogenesis begin for the upcoming spawning event in spring. Our objective was to assess whether early gonad recrudescence was a period of sensitivity for inducing immunomodulation. Adult largemouth bass (LMB; Micropterus salmoides) were exposed in outdoor pond mesocosms from post-spawning (July) through early gonad recrudescence (November) to either a model estrogen, 17alpha-ethinylestradiol (EE2; 2.4 ng/L), a mixture of endocrine-active substances commonly detected in the Chesapeake Bay watershed (MIX; 5.4 µg atrazine/L and 47.9 ng estrone/L), or a solvent control. Immune endpoints including mitogenesis and respiratory burst were assessed in fish sampled during December and April.