Science Serving Maryland's Coasts
Michael Wilberg, Ph.D.
Chesapeake Biological Laboratory
Estimation of Site-Specific Mortality Rates of Eastern Oyster Crassostrea virginica in Chesapeake Bay and Causes of Regional Variation
The eastern oyster, Crassostrea virginica, is a culturally and socially valuable species that is declining rapidly in Chesapeake Bay. To estimate site-specific mortality rates from relative age class abundance, I generated cohort specific catch curves and compared the results to corresponding regional anthropogenic and environmental data, including harvest and August bottom dissolved oxygen, water temperature and salinity. Harvest and mortality, though there is high uncertainty (p = 0.67; α = 0.05), have a slight negative relationship. A strong negative relationship, though not significant (p = 0.06; α = 0.05), exists between dissolved oxygen and mortality. Despite what may be expected, there is a highly significant negative relationship between temperature and mortality (p = 0.01; α = 0.05). Salinity and mortality have a negative relationship (p = 0.13; α = 0.05). This suggests that of all the observed anthropogenic and environmental factors affecting oyster mortality, bottom temperature has the greatest influence on oyster mortality, followed by the effects of decreasing bottom dissolved oxygen levels, salinity and harvest.
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