Meeting Abstract
We studied movements of Blue crabs (Callinectes sapidus) in a wind driven system during Summer (August) 2012 and Fall (October) 2014. Free ranging crabs were tracked using radio frequency identification tags and antenna arrays deployed along a Canal connecting Lake Mattamuskeet to Pamlico Sound. Co-located and simultaneous meteorological and physical oceanographic instruments provided environmental data as context for crab movements. The environment in the summer was dominated by atmospheric pressures changing gradually between 1010 and 1024 hPa, south/south westerly winds generally < 4 m/s, air temperatures that fluctuated diurnally between 21 and 31 C and water temperatures changing gradually between 26 and 30 C. Crabs showed foraging movements up and down the canal. The fall was dramatically different. Atmospheric pressures ranged between 1002 and 1024 hPa with relatively rapid pressure changes in 2 to 3 days with passing fronts. North winds often greater than 5 m/s alternated with periods of winds similar to the summer pattern. Air temperatures fluctuated diurnally about 10 C and between 25 C and 6 C. Water temperatures lagged behind air temperatures and ranged from 26 C to 9 C. Water temperatures gradually decreased until they responded to a cold front that dropped the air temperature 19 C and the water temperature dropped briefly below 13.3 C, the lower activity limit of blue crabs. When the water warmed back up crabs initiated unidirectional migration toward the sound. Temperature shock appears to be the proximate cue that initiates the fall migration down estuary.
