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ROLE OF ANTHROPOGENIC AND ENVIRONMENTAL VARIABLE ON THE PHYSIOLOGICAL AND ECOLOGICAL RESPONSES OF OYSTERS IN SOUTHWEST FLORIDA ESTUARIES
Citation:
Volety, A. K., M. Savarese, J T. Winstead, AND S. G. Tolley. ROLE OF ANTHROPOGENIC AND ENVIRONMENTAL VARIABLE ON THE PHYSIOLOGICAL AND ECOLOGICAL RESPONSES OF OYSTERS IN SOUTHWEST FLORIDA ESTUARIES. Presented at 96th Annual Meeting (Aquaculture 2004) of the National Shellfisheries Association, Honolulu, HI, March 1-5, 2004.
Description:
The role of freshwater alterations and seasonal changes on the ecological and physiological responses of oysters were investigated in the Caloosahatchee River, Estero Bay and Faka-Union estuaries in SW Florida. Condition index, oyster density, and disease incidence of Perkinsus marinus were measured through monthly sampling at three comparable sites located along the main salinity gradient in Estero Bay and Faka-Union estuary, while spat recruitment, juvenile growth, and gonadal index of oysters were also measured monthly at five locations along the salinity gradient in the Caloosahatchee River.
Sharp declines in temperature and salinities resulted in decreased P. marinus infections in oysters from all locations. Antagonistic effects of temperature and salinity on P. marinus infections make trends difficult to discern. Oysters from Faka-Union, an estuary that receives excessive freshwater, have a significantly lower condition index compared to a more natural estuary, Estero Bay (Fig. 1). Condition index in oysters from all three estuaries was influenced by the reproductive activity. Oyster density was higher in the upper-mid estuary and decreased with increasing distance offshore in the Estero Bay and the Caloosahatchee River, while none to few oysters are present at the upstream locations in the Faka-Union estuary. Only the downstream-most site showed appreciable living densities, a pattern consistent with predicted effects of watershed alteration and freshwater inundation. Oysters in SW Florida estuaries appear to continuously spawn between March/April - October, with upstream oysters spawning earlier than the downstream oysters. Freshwater releases from Lake Okeechobee into the Caloosahatchee River in spring/summer months resulted in >95% mortality of juvenile oysters and pushed the loci of spat recruitment to more downstream locations.
We are communicating the results of our study with resource managers who are utilizing them to adjust the quantity and timing of freshwater releases into the estuaries. The use of adaptive management approaches involving freshwater releases to sustain and enhance oyster populations is valuable to the ecology of SW Florida estuaries.