Date of Award

Fall 1992

Document Type


Degree Name

Master of Science (MS)


Biological Sciences



Committee Director

Raymond W. Alden, III

Committee Member

Cynthia M. Jones

Committee Member

Daniel M. Dauer

Call Number for Print

Special Collections LD4331.B46 S543


This study is the first to focus on the assemblages of the planktonic mysids, decapods, and sergestids found in the lower Chesapeake Bay. The assemblages of these organisms in the lower Chesapeake Bay and nearby shelf were characterized using three different statistical approaches, and the methods used were evaluated for their effectiveness at delineating ecologically meaningful assemblages. Three stations were sampled across the Chesapeake mouth and one offshore, with oblique and neuston net tows. Twenty-seven larval stages, representing at least 23 species, were found in sufficient numbers to be analyzed statistically. The statistical approaches were each based upon a different initial clustering analysis: 1) the divisive VARCLUS analysis; 2) the ANOVA-based partitioned agglomerative approach of Williams and Stephenson (1973); and 3) the Canberra metric: a commonly used representative of traditional agglomerative clustering analyses. The VARCLUS analysis was by far the most successful at suggesting species associations, followed by the Williams and Stephenson analysis, which was primarily useful as a summarization of major temporal and spatial patterns. Major species associations included Uca spp. and Upogebia affinis zoea; juveniles and adults of two mysid species (Neomysis americana and Mysidopsis bigelowi); and associations between larval stages of Callirzectes and Squilla. Major seasonal patterns found were the abundance of Cancer irroratus and Crangon septemspinosa in the spring, the predominance of decapod larvae in the late summer, and the fall and spring migrations of the two mysids. The major spatial pattern was the prevalence of the larvae of most taxa in oblique samples from the bay mouth. The multivariate methods proved most useful as data summaries, providing different perspectives for exploration and hypothesis generation.


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