Abstract
Hard clams are important constituents of shallow, benthic habitats along the eastern United States. In Southwest Florida, two species (Mercenaria mercenaria and M. campechiensis) historically were abundant, but declines from overharvesting and diminishing water quality have greatly reduced local abundance. In the Charlotte Harbor Estuary (CHE), restoration efforts are underway to facilitate recovery of hard clam populations to improve water quality, but little is known about the population status of these clams or the habitat characteristics where they reside in this region. The purpose of this study was to a) investigate hard clam distributions with respect to habitat characteristics in the CHE and b) to determine the impact of environmental conditions on their burrowing efficiency. Burrowing is necessary for of clam survival, and environmental conditions, including sediment grain size, are known to influence the ability of clams to burrow, yet limited research has been conducted on this genus. In this study, clam distributions were patchy across spatial and temporal scales, not seemingly correlated with one single habitat characteristic, but rather a combination of characteristics. Hard clams were found to prefer coarse sand mixtures over shell hash or fine sand. Burrowing activity was reduced in clams in shell hash and exposed to low salinity (20 ppt) under laboratory conditions. The results of this study suggest that burrowing is reduced under adverse conditions. These data will be incorporated into a Habitat Suitability Index model and should be considered for future restoration efforts.
