Date Awarded


Document Type


Degree Name

Doctor of Philosophy (Ph.D.)


Virginia Institute of Marine Science


Herbert M. Austin


Five fishery independent data sets were used to investigate multispecies fish recruitment patterns in Chesapeake Bay (1966--1997). Despite differences in sampling gear, sampled habitat, collection methods, and sampling sites, the strongest multispecies recruitment patterns within each data set (revealed by separate principal components analyses) depict a negative relationship between recruitment of spring spawning anadromous fishes and fall-winter continental shelf spawning species. This pattern dominates both low and high frequency components of the multispecies data. Because these two species groups utilize freshwater and oligohaline reaches of the Bay and its tributaries as springtime nursery areas, this Chesapeake Bay Anadromous-Shelf Spawner (CBASS) recruitment pattern was compared to spring climatic variability in the Mid Atlantic region. Using principal components analysis, cluster analysis, and a gridded sea level pressure (SLP) data set, an objective circulation classification technique identified ten synoptic-scale SLP patterns responsible for spring (Mar--May) weather conditions and interannual seasonal climate variability. Classification and regression tree modeling, ordinary least squares, and least trimmed squares regression were used to compare covariability between the CBASS recruitment pattern and the thirty (3 months x 10 patterns) monthly frequency pressure pattern time series. March frequencies of two regional pressure patterns, the Azores-Bermuda and Ohio Valley high pressure systems, were found to account for a large portion of the CBASS pattern's variability. Spring conditions in March, brought on by an early appearance of the Azores-Bermuda High, favor recruitment of shelf spawners while prolonged winter conditions, brought on by a relative dominance of the Ohio Valley high, favor anadromous spawning success. These observations are supported by an analysis of March temperature and precipitation anomaly patterns for the continental U.S. Analyses of hydro-climatic, species specific zooplankton density, and juvenile fish abundance variables for three Bay tributaries demonstrate that the timing of the winter--spring transition differentially influences nursery area habitat suitability in a pattern consistent with the climate-CBASS recruitment relationships described in this study. The climate-recruitment relationships described in this study represent a multivariate variant of Cushing's Match-Mismatch hypothesis.



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