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INVESTIGATIONS INTO THE EFFECTS OF SEASON AND WATER QUALITY ON OYSTERS (CRASSOSTREA VIRGINICA) AND ASSOCIATED FISH ASSEMBLAGES IN THE CALOOSAHATCHEE RIVER ESTUARY, FLORIDA: IMPLICATIONS OF ALTERED FRESHWATER INFLOW
Citation:
Volety, A. K., S. G. Tolley, AND J T. Winstead. INVESTIGATIONS INTO THE EFFECTS OF SEASON AND WATER QUALITY ON OYSTERS (CRASSOSTREA VIRGINICA) AND ASSOCIATED FISH ASSEMBLAGES IN THE CALOOSAHATCHEE RIVER ESTUARY, FLORIDA: IMPLICATIONS OF ALTERED FRESHWATER INFLOW. Presented at Charlotte Harbor Watershed Summit, Punta Gorda, FL, Feb 7-9, 2002.
Description:
A suite of biological and ecological responses of a Valued Ecosystem Component species, Crassostrea virginica, was used to investigate ecosystem-wide health effects of watershed alterations in the Caloosahatchee River estuary, Florida. The influence of water quality and season on disease prevalence and intensity, gonadal condition, recruitment potential, and growth of oysters, and on the habitat suitability of oyster reefs for fishes and macrobenthos were examined. Oysters (10) were sampled monthly at each of five locations within the Caloosahatchee River estuary: Piney Point, Cattle Dock, Kitchel Key, Bird Island, and Tarpon Bay. Higher temperatures and salinities favored the oyster parasite Perkinsus marinus, and histological analyses revealed the presence of several additional parasitic or commensalistic organisms. Comparison of mortality among sites indicated that juvenile oysters tolerated salinities of 15-38 ppt. Spat recruitment was higher at subtidal (1-5 spat/shell; Piney Point, Bird Island, and Tarpon Bay) than at intertidal locations (Kitchel Key, and Cattle Dock), where spare oyster distribution and swift currents appeared to limit settlement success. The late peak in gametogenesis (August-September) observed at all sites may have resulted from reduced salinities during May-July or may imply that oysters spawn twice per season. Most of the oysters showed the presence of the protozoan parasite Nematopsis spp., hydroid polyps Eutima spp., the diagenetic trematode parasites Echinostoma spp. and Bucephalus spp., and larvae of the cestode Tylocephalum spp. Oysters are intermediate hosts for these parasites, with mud crabs, birds, and sting rays serving as primary hosts. Xanthid and porcellanid crabs were the dominant macrobenthos associated with oyster reefs in the lower estuary with estimated densities ranging from 2.9-5.1 and 0.4-6.0 individuals per liter of oysters respectively. Reef-resident fishes included Opsanus beta, Chasmodes saburrae, Gobiosoma bosc, and Gobiesox strumosus with associated densities lower than those of the dominant macroinvertebrates. Overall, results suggest that periodic freshwater releases may benefit oysters by lowering the salinity and thus the intensity of parasite infection (Perkinsus marinus). It should be cautioned that the long-term effects of low salinity on oysters have not been investigated. This study was made possible by a grant from the South Florida Water Management District administered through Florida Atlantic University and the Florida Center for Environmental Studies.