Variation in Planktonic Availability and Settlement of Blue Crab Megalopae in the York River, Virginia

Blue crab, Callinectes sapidus, megalopae and juveniles were sampled in the plankton and on natural (grassbeds) and artificial settlement substrates (collectors) at two sites in each of two areas of a lower Chesapeake Bay tributary (York River, Virginia) to examine spatial variability in blue crab recruitment. Spatial patterns of abundance were not consistent across habitats (plankton, artificial collectors and grassbeds) or time. Densities of planktonic megalopae were homogeneous at 1–2 m (within site) but varied at spatial scales of hundreds of meters (between sites) and kilometers (between areas). Settled megalopae were distributed unevenly within and between sites, but their abundance did not differ between areas. Densities of megalopae and first-stage juveniles in grass beds correlated with megalopal abundance in the plankton. Settlement on collectors, however, was not correlated with planktonic density, probably because of low sample size. Total juvenile abundance exhibited lower spatial and temporal variability in grassbeds than that of megalopae or first-stage juveniles, suggesting high post-settlement mortality or migration from areas of high settlement.