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 chance of opportunistic bacterial infections. Several microbial pathogens including Flavobacterium columnare, Aeromonas spp. and largemouth bass virus (LMBV) have also been cultured from clinically diseased YOY. A multiplex fluorescence in situ hybridization (FISH) assay was developed to determine potential co-localization of M. inornatus, Flavobacterium spp., and Aeromonas spp. infections. With FISH, 75% of YOY SMB exhibited M. inornatus infections, 10% had Aeromonas spp. infections, and 5% had Flavobacterium spp. infections, while 3% had coinfections with both bacterial species and M. inornatus. The results of the multiplex FISH assay revealed a low occurrence of coinfections of Flavobacterium spp. and/or Aeromonas spp. with M. inornatus in randomly sampled individuals.

Zequanox® is a commercial formulation of the killed bacterium, Pseudomonas fluorescens (strain CL145A) that has USEPA approval for use in open water to kill dreissenid mussels. Previous nontarget studies demonstrated the safety and selectivity of the product, but the database is limited for macroinvertebrate taxa and exposure conditions. We evaluated the safety of the product to two high value macroinvertebrates, the amphipod Gammarus lacustris lacutris, and nymphs of the burrowing mayfly, Hexagenia spp., at the maximum approved concentration (100 mg/L A.I.) and exposure duration (8 h). Survival of animals was measured at the end of 8 h exposure and at 24 h post-exposure and 96 h post-exposure. Additionally, histological changes in the digestive tract of both species were compared with controls at 96 h post-exposure. The results showed no effect of Zequanox on survival of either species. Survival of G. lacustris exceeded 85% in all concentrations at all three sampling time points. Survival of Hexagenia spp. ranged from 71% (control) to 91% (50 mg/L) at 8 h, 89-93% at 24 h post-exposure and 70-73% at 96 post-exposure h across all treatments. We also saw no evidence of pathology in the visceral organs of treated animals. Our results indicate that application of Zequanox at the maximum approved concentration and exposure duration does not cause acute mortality or pathology to G. lacustris and Hexagenia spp.

Zequanox® is a commercial formulation of the killed bacterium, Pseudomonas fluorescens (strain CL145A) that has USEPA approval for use in open water to kill dreissenid mussels. Previous nontarget studies demonstrated the safety and selectivity of the product, but the database is limited for macroinvertebrate taxa and exposure conditions. We evaluated the safety of the product to two high value macroinvertebrates, the amphipod Gammarus lacustris lacutris, and nymphs of the burrowing mayfly, Hexagenia spp., at the maximum approved concentration (100 mg/L A.I.) and exposure duration (8 h). Survival of animals was measured at the end of 8 h exposure and at 24 h post-exposure and 96 h post-exposure. Additionally, histological changes in the digestive tract of both species were compared with controls at 96 h post-exposure. The results showed no effect of Zequanox on survival of either species. Survival of G. lacustris exceeded 85% in all concentrations at all three sampling time points. Survival of Hexagenia spp. ranged from 71% (control) to 91% (50 mg/L) at 8 h, 89-93% at 24 h post-exposure and 70-73% at 96 post-exposure h across all treatments. We also saw no evidence of pathology in the visceral organs of treated animals. Our results indicate that application of Zequanox at the maximum approved concentration and exposure duration does not cause acute mortality or pathology to G. lacustris and Hexagenia spp.

Plasma from adult smallmouth bass was analyzed for 13 per- and polyfluoroalkyl compounds at 11 sites for a spatial comparison. At four sites a temporal comparison was made over a three year period (2017-2019). At two sites tissue comparisons were made using plasma, whole blood, liver, gonad and muscle. Compounds detected at least once are included in the dataset. For all fish collection site, date of collection, sex, age, length and weight are also documented.

Plasma from adult smallmouth bass was analyzed for 13 per- and polyfluoroalkyl compounds at 11 sites for a spatial comparison. At four sites a temporal comparison was made over a three year period (2017-2019). At two sites tissue comparisons were made using plasma, whole blood, liver, gonad and muscle. Compounds detected at least once are included in the dataset. For all fish collection site, date of collection, sex, age, length and weight are also documented.

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).

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 date of collection, length, weight and age of each adult smallmouth bass were documented. Four compounds were detected in every plasma sample, while two additonal compounds were only occasionally observed at low concentrations.

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.

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.

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.