Risk factors associated with mortality of age-0 Smallmouth Bass in the Susquehanna River basin, Pennsylvania

Journal of Aquatic Animal Health
By: , and 



Evidence of disease and mortalities of young of the year (age‐0) Smallmouth Bass Micropterus dolomieu has occurred during the late spring and summer in many parts of the Susquehanna River watershed since 2005. To better understand contributing factors, fish collected from multiple areas throughout the watershed as well as out‐of‐basin reference populations (Allegheny and Delaware River basins; experimental ponds, Kearneysville, West Virginia) were examined grossly and histologically for abnormalities. Tissue contaminant concentrations were determined from whole‐body homogenates, and water contaminant concentrations were estimated using time‐integrated passive samplers at selected sites. Observed or isolated pathogens included bacteria, predominantly motile Aeromonas spp. and Flavobacterium columnare ; largemouth bass virus, and parasites, including trematode metacercariae, cestodes, and the myxozoan Myxobolus inornatus . Although these pathogens were found in age‐0 Smallmouth Bass from multiple sites, no one pathogen was consistently associated with mortality. Chemicals detected in tissue included polychlorinated biphenyl (PCB) congeners, organochlorine, and current‐use pesticides. Pyraclostrobin, PCB congeners 170 and 187, cis‐chlordane and trans‐nonachlor were detected in all Susquehanna watershed samples but rarely in samples from the reference site. The findings support the idea that there is no single cause for disease of age‐0 Smallmouth Bass; rather the cumulative effects of co‐infections and potential immunomodulation by environmental stressors during a sensitive developmental life stage may lead to mortality. Identifying the most important risk factors will be necessary for more in‐depth analyses of individual stressors and better management of the habitat and fish populations.

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Publication type Article
Publication Subtype Journal Article
Title Risk factors associated with mortality of age-0 Smallmouth Bass in the Susquehanna River basin, Pennsylvania
Series title Journal of Aquatic Animal Health
DOI 10.1002/aah.10009
Volume 30
Issue 1
Year Published 2018
Language English
Publisher Wiley
Contributing office(s) Columbia Environmental Research Center, Leetown Science Center, New Jersey Water Science Center
Description 16 p.
First page 65
Last page 80
Country United States
State Pennsylvania
Other Geospatial Susquehanna River basin
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