Patches of crab megalopae in the mouth of Delaware Bay--an analysis ofspatial scales

摘要

Recent studies have shown that zoea larvae of brachyuran crabs often occur in patches that are formed at spawning and persist on time scales ranging from days to at least a week. In the present work we investigated the spatial distribution of the megalopal stage of 2 taxa of brachyurans (Callinectes sapidus and Uca spp.) in Delaware Bay on the east coast of North America (ca. 38.6 degree N, 75.2 degree W). We used a combination of high-frequency plankton sampling and data from a moored current meter to characterize the length scale of patches of megalopae at a single station in the mouth of the bay. The study consisted of 12 separate sampling periods during the late summers of 2001 and 2002. During each period, plankton were collected every 10 min over a single flood-tidal phase. Current-velocity data were collected simultaneously via an S-4 current meter moored at the station. Subsequent analysis demonstrated the transport of patches of megalopae past the station during five of the sampling periods. The radius of the patches was determined through autocorrelation analysis. The radii of patches of C. sapidus megalopae ranged from approximately 500-2,000 m, whereas the radii for Uca patches was typically smaller with values around 500 m. This patchy distribution has important consequences for transport and settlement of the megalopae in juvenile habitat.