Date of Award

Summer 1985

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Biological Sciences

Program/Concentration

Biology

Committee Director

Ray S. Birdsong

Committee Member

James Matta

Committee Member

Lloyd Wolfinbarger

Committee Member

Steve Ackerman

Call Number for Print

Special Collections LD4331.B46 S57

Abstract

Seven enzymes extracted from heart and liver tissues of American shad Alosa sapidissima captured during migrations into the Chesapeake Bay and Nansemond River were electrophoretically surveyed. Malate dehydrogenase and nonspecific esterase displayed polymorphic loci. The esterase polymorphism was used as a biochemical genetic marker to analyze the shad migration through the southern Chesapeake Bay. The genetic composition of the shad migration changed significantly over time indicating that this migration is probably composed of multiple, genetically divergent spawning populations. Results of this study are subject to differing interpretations. Observed temporal heterogeneity may result from separation of northern and James River stocks as the migration proceeds through this region. Alternatively, a differential migration of populations may occur with certain populations entering Chesapeake Bay in advance of other populations. High homozygosity of a collection from the Nansemond River was attributed to sampling a smaller gene pool of individuals that had segregated from the main migration by homing to natal spawning grounds. Evidence is presented to suggest that esterase alleles respond differentially to cold and warm water temperatures, and may influence the timings of shad migrations.

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DOI

10.25777/bfg2-tg24

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