Semester

Fall

Date of Graduation

2020

Document Type

Dissertation

Degree Type

PhD

College

Davis College of Agriculture, Natural Resources and Design

Department

Not Listed

Committee Chair

Patricia M. Mazik

Committee Member

Stuart Welsh

Committee Member

Kyle Hartman

Committee Member

Vicki S. Blazer

Abstract

White perch are an abundant demersal fish species in freshwater and oligohaline habitats of the Chesapeake Bay. An avoidance of salinity > 12-15 ppt generally restricts the distribution and movements of fish to within tributaries in the mid to lower Bay, which over time has resulted in the formation of at least three separate stocks in Chesapeake Bay. Sub-populations of white perch that are partially isolated may serve as sentinels of the conditions or stressors in the tributaries in which they reside. Fish are exposed to a variety of environmental contaminants and other anthropogenic stressors that can vary in magnitude based on regional differences in land-use patterns. Health studies of white perch conducted in the 1980s and 1990s revealed a variety of hepatic lesions, including two reports of liver neoplasms, which suggested a sensitivity to degraded habitat or pollution. However, surveys to determine prevalences and potential etiologies of tumors were not determined and the health of white perch in Chesapeake Bay was not investigated again until the studies reported herein. Recent health investigations has revealed associations between neoplasms (cholangiocarcinomas) and bile duct parasites (coccidian and myxozoan) that were not previously described from white perch. These findings raised questions concerning the potential roles of contaminants and parasitism in liver tumor induction in this species. To address knowledge gaps associated with the prevalence and etiology of tumors in white perch, an assessment of environmental contaminants, biomarkers of exposure, biliary parasites, and liver histopathology was required. This study was conducted in two tributaries of the Bay: the Choptank River, an eastern shore tributary with extensive watershed agriculture, and the Severn River, a western shore tributary with extensive development. This dissertation addresses: 1) descriptions and taxonomic placement of the coccidian and myxozoan parasites; 2) measurement of waterborne concentrations of polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides, and brominated diphenyl ethers; 3) detection of biliary metabolites as a biomarker of exposures to PAHs; 4) a histopathological description of parasitic infections, neoplasms and other lesions in the liver of fish; 5) an assessment of the biological and anthropogenic risk factors for neoplasia; and 6) an assessment of splenic and hepatic macrophage aggregates as an alternate biomarker of contaminant exposure.

Download

Share

COinS