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EFFECTS OF FRESHWATER RELEASES AND SEASON ON OYSTERS (CRASSOSTREA VIRGINICA) IN CALOOSAHATCHEE ESTUARY, FLORIDA
Volety, A. K., S. G. Tolley, AND J T. Winstead. EFFECTS OF FRESHWATER RELEASES AND SEASON ON OYSTERS (CRASSOSTREA VIRGINICA) IN CALOOSAHATCHEE ESTUARY, FLORIDA. Presented at 94th Annual Meeting of the National Shellfisheries Association, Mystic, CT, April 14-18, 2002.
The influence of freshwater releases and season on disease prevalence and intensity of Perkinsus marinus, condition index, gonadal condition, recruitment potential, and growth of oysters was examined monthly at five locations along the Caloosahatchee estuary, Florida. Temperatures and salinities at the study sites ranged from 16-33 ?C and 3-39 ppt respectively. Higher temperatures and salinities favored P. marinus. While prevalence of P. marinus ranged from 0 (after heavy rainfall and/or freshwater water releases) -70% (during dry winter months), overall intensity was light (0-1.3). Comparison of mortality among sites indicated that juvenile oysters tolerated salinities of 5-38 ppt. Condition index of oysters was influenced by reproductive cycle and spawning events. Spat recruitment (1-5 spat/shell) and growth of juvenile oysters was higher at subtidal than at intertidal locations, where sparse oyster distribution and swift currents appeared to limit growth and settlement success. Oysters were reproductively active between March and October, with peak reproduction occurring from June-October. Overall, results suggest that periodic short-term freshwater releases may benefit
oysters by lowering the salinity and thus the intensity of Perkinsus marinus. Laboratory studies suggest that adult oysters can tolerate low salinities (3 ppt) for 102 weeks. Given high salinities and infection intensities during winter months, it is recommended that freshwater releases take place during winter instead of current summer releases.