The formation, characterization, and transport of brachyuran larval patches: A spatio-temporal analysis

Understanding the distribution and transport of brachyuran larval forms is germane to understanding the dynamics of juvenile as well as adult populations. 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. Related studies have also shown that post-larval stages of brachyuran crabs settle in a similar (i.e., patchy) distribution. The research conducted in this dissertation focused on the biological formation and transport of early-stage larval patches as well as the structure and transport of post-larval patches on the inner shelf and in a secondary estuary (i.e., juvenile nursery area).; Through Chi square analysis gravid crabs were shown to utilize tidal currents to facilitate their migration in and out of the bay and that the majority of crabs using outgoing, tidal currents had hatch-imminent egg masses. The second part of this study applied a hydrodynamic model (ECOM3d) to determine the location of patches of newly hatched blue crab larvae. Results showed the majority of the modeled patch origins were offshore and downshelf of the bay mouth. Patches located in these areas may have a higher probability of being retained near the Delaware Bay (Garvine et al. 1997).; The length scales of megalopal patches were characterized as they were being transported from the inner shelf into the Bay. The dimension of the patches (300–1500 m) was determined through autocorrelation analysis. The present data, combined with results of previous work, suggest that individual patches of crab larvae may remain coherent through the entire period of zoeal and megalopal development.; The length scales of megalopal patches were characterized as they were being transported into a river (nursery area) during an extended downwelling event and a comparable quiescent period. Through autocorrelation analysis the dimension of the patches was determined to range from 400 to 450 m. Patches of Callinectes sapidus (blue crab) megalopae only occurred during the downwelling event. This supports the conceptual idea that blue crab megalopae rely on southward wind events for across-shelf transport to estuarine nursery areas.