Eastern oysters, Crassostrea virginica (Gmelin 1791), were sampled from seven Florida estuaries from January 2005 through December 2007 as part of the prerestoration monitoring and assessment component of the Comprehensive Everglades Restoration Plan. Study locations included Tampa Bay, Mosquito Lagoon, Sebastian River, St. Lucie estuary (3 study sites), Loxahatchee River (2 study sites), Lake Worth Lagoon, and Biscayne Bay. Settled oyster density was monitored twice per year at stations within each study site. Oyster recruitment, water temperature, and salinity were monitored on a monthly basis. Salinity varied greatly among the estuaries, and each study site fell into 1 of 2 primary salinity regimes: one relatively stable and with higher salinities (mean range, 24–35), and the other more variable and with lower salinities (mean range, 12–17). All 7 estuaries were impacted, to varying degrees, by the relatively active 2005 tropical storm season as well as local water management practices during the study. Two of the estuaries, St. Lucie and the Sebastian River, were severely impacted by controlled introductions of freshwater, which decreased salinities below the range that oysters can tolerate. As a result, live oysters were virtually absent from the study sites in both estuaries in 2005, when the freshwater introductions were most pronounced. At the opposite extreme, long-term reduction of freshwater flow into Biscayne Bay has exacerbated already increasing salinities and has resulted in the absence of reef-building oysters at that study site. Oysters were present at all other study sites, but densities were lower in 2005 than in subsequent years because of substantial salinity decreases after tropical storms in 2004 and 2005. The greatest and most stable oyster densities were found in Tampa Bay, where mean oyster density reached 400/m2 by fall 2007. Recruitment was observed at each site on recruitment arrays retrieved from April through December, although the timing, duration, and intensity of the recruitment season varied annually and among study sites. The Tampa Bay, Mosquito Lagoon, Loxahatchee River, and Lake Worth Lagoon sites exhibited a bimodal recruitment pattern with peaks in the spring and fall. At the remaining sites, which were the most strongly affected by water management practices, recruitment patterns were sporadic and inconsistent throughout the study. The lowest recruitment rates occurred in 2005, when the density of settled oysters was also low, presumably because of reduced salinities resulting from a combination of active tropical storm seasons and controlled freshwater introductions.
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Vol. 32 • No. 3