The Role of Tidal Fronts in Maintaining Patches of Brachyuran Zoeae in Estuarine Waters

Brachyuran larvae were sampled along a 200-m, NE-SW transect crossing a tidal front in lower Delaware Bay. Concentrations of the larval mud crab Neopanope sayi ranged from approximately 30 zoeae·m―3 NE of the front to more than 7,000 zoeae·m―3 SW of the front with an intermediate concentration in the front. Zoeal stages I and II were most abundant at each sampling site, suggesting that the patch of N. sayi resulted from a spawning event that occurred 4-5 days earlier. Physical concentrating mechanisms associated with the front, combined with vertical movements by the larvae, appeared to be responsible for maintaining the concentrated patch of larvae of N. sayi.