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A Retrospective Time Series Analysis Of Oyster, Crassostrea Virginica, Recruitment (1946-1993)
Austin, Herbert Evans, David Haven, Dexter
Austin, Herbert
Evans, David
Haven, Dexter
Abstract
Temporal patterns of eastern oyster, Crassostrea virginica (Gmelin 1791), spatfall in the Virginia tributary rivers to the Chesapeake Bay showed a decline in all rivers from 1946 through the early 1970s, with a subsequent leveling off. The decline was most severe in the James and less so moving north to the York and Rappahannock Rivers; it was least severe in the Potomac River. Yearling patterns generally mirrored the spat. Cluster analyses grouped the bars naturally by up- and downriver spatfall patterns. They also clustered this way when between-river comparisons were made. Spatfall showed a significant cross-correlation with yearlings a year later in all Virginia rivers, which suggests that the ''yearling'' designation was accurate and that spat counts may be used to predict yearling abundance. The relation of spat to later seed was significant for the James River at 2 and 3 y, but none was found between spat and market oyster. James River seed demonstrated a slightly significant relation to market oyster 4 y later. Regression analyses between spat counts and spring and summer water temperatures and river discharge produced little explanation of spat variation. There was, however, a significant relation between spat count and the Palmer Drought Index. The drought index is a combination of rainfall, soil type, and evapotranspiration. When the period of the greatest change in the drought index was correlated with spatfall, there was found to be a significant 2- to 4-y lag. We suggest that this reflects a response by the ecosystem to changing environmental conditions.
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1996
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austin1996.pdf
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Fisheries Science Peer-Reviewed Articles, Oyster; Crassostrea Virginica; Recruitment; Spat; Yearling Oyster
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Virginia Institute of Marine Science