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EFFECTS OF SEASONAL AND WATER QUALITY PARAMETERS ON OYSTERS (CRASSOSTREA VIRGINICA) AND ASSOCIATED FISH POPULATIONS.
Citation:
Volety, A. K., S. G. Tolley, AND J T. Winstead. EFFECTS OF SEASONAL AND WATER QUALITY PARAMETERS ON OYSTERS (CRASSOSTREA VIRGINICA) AND ASSOCIATED FISH POPULATIONS. Presented at 16th Biennial Conference of the Estuarine Research Foundation: ERF 2001: An Estuarine Odyssey, St. Pete Beach, FL, Nov 4-8, 2001.
Description:
Influence of water quality and seasonal changes on disease prevalence and intensity of Perkinsus marinus, gonadal condition, recruitment potential, growth of caged juvenile oysters, and habitat suitability of reefs for fishes and macrobenthic invertebrates were measured in Callosahatchee estuary. Oysters (10) were sampled monthly at each of five locations. Disease intensity and prevalence appeared to be controlled by temperature and salinity with higher temperatures and salinities favoring the parasite. No significant mortality was observed in juvenile oysters at the sampling locations (except one location) indicating that oysters were able to tolerate both the low (15 ppt) and high salinities (35-38 ppt). Mortality of juvenile oysters appears to be due to water quality and or water currents created by boat wakes. Spat recruitment was moderate (1-5 spat/shell) in subtidal locations and lower at intertidal locations. The intertidal habitat of oysters (and thus sparse distribution) combined with swift water currents appears to influence lower spat settlement. Oysters at all sites were at their peak gametogenic cycle during August-September, a period late for spawning of oysters. It is not clear whether oysters delayed spawning activity to later months due to reduced salinities during May-July 2000, or if oysters spawn twice in a season. Histological analyses revealed the presence of several commensalistic or parasitic organisms belonging to Nematopsis spp., Eutima spp., Echinostoma spp., Bucephalus spp., and Tylocephalum spp. Xanthid crab Eurypanopeus depressus and the porcelain crab Petrolisthes armatus were the dominant members of the oyster reef community in the lower Callosahatchee Estuary with estimated densities ranging from 2.87-5.07 and 0.36-6.24 individuals per liter of oysters respectively. Reef-resident fishes collected included Opsanus beta, Chasmodes saburrae, Gobiosoma bosc, and Gobiesox strumosus. Results suggest that periodic freshwater releases into the Caloosahatchee Estuary may benefit oysters by lowering the salinity and thus the lower intensity of parasite, Perkinsus marinus. It should be cautioned that the long-term effects of low salinity (< 10 ppt) on oysters have not been investigated. Potential sites for restoration of oyster reefs are identified.