Billions of larval blue crabs, or zoeae, are spawned each year into the many estuaries and bays of the Atlantic and Gulf coasts of the United States. These tiny translucent animals, comparable in size to the tips of fine sewing needles, only faintly resemble adult blue crabs.  A small fraction of zoeae successfully navigate the tides and currents many miles to the seaward margin of the continental shelf, develop through a series of larval stages, and eventually return as megalopae...