Blue crab settlement and recruitment patterns in shallow estuarine habitats of Texas

During September 2003-October 2005, we investigated spatio-temporal patterns of blue crab terminal settlement and juvenile recruitment rates in shallow (14-103 cm) estuarine habitats.  We collected data at three replicate study sites within Aransas National Wildlife Refuge, Texas using settlement collectors highly modified in dimension and floating orientation from standard protocol.  Monitoring of megalopal settlement and juvenile recruitment rates (no./semi-lunar collection period) in bay habitat revealed events were of highest frequency and magnitude in March-June and August-October.  Megalopae were developmentally advanced when arriving to sites, as the percentage of settlers representing recruits (recently-metamorphosed juveniles; 27-93%) markedly increased with only slight change in distance (51-59 km) from the nearest larval source.  We determined water temperature before and during embryonic development was the best predictor of settlement, whereas recruitment was most influenced by recent levels of precipitation.  We also deployed collectors within each of three interior salt-marsh habitats (tidal creek, connected pond, unconnected pond) per site and determined the spatial extent to which megalopae settled in the salt-marsh and were recruited into the crab population increased with mobility associated with advancing development.  In summary, significant progress was made in identifying environmental conditions and habitats important to terminally settling and metamorphosing megalopal blue crabs.