Environmental and endogenous control of selective tidal-stream transport behavior during blue crab <Emphasis Type="Italic">Callinectes sapidus</Emphasis> spawning migrations |
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Authors: | M Zachary Darnell Thomas G Wolcott Dan Rittschof |
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Institution: | (1) Duke University Marine Laboratory, Nicholas School of the Environment, 135 Duke Marine Lab Rd., Beaufort, NC 28516, USA;(2) Department of Marine, Earth, and Atmospheric Sciences, North Carolina State University, Raleigh, NC 27695, USA;(3) Present address: Marine Science Institute, The University of Texas at Austin, 750 Channel View Dr., Port Aransas, TX 78373, USA |
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Abstract: | Selective tidal-stream transport (STST) is used by many estuarine organisms. Spawning blue crabs use a form of STST, ebb-tide
transport (ETT), to migrate to high-salinity areas of the lower estuary and coastal ocean for larval release. In tidal estuaries,
ETT is driven by a circatidal rhythm in vertical swimming with episodic ascents into the water column during ebb tide. This
study examined vertical swimming behavior of migrating female blue crabs tethered in habitats they could encounter during
migration. A combined bio-physical field study in the summer of 2009 simultaneously measured physical parameters of the water
column and vertical swimming behavior of tethered ovigerous crabs using pressure-recording dataloggers. Tethering sites were
in the tidal Beaufort Inlet drainage and the non-tidal Albemarle-Pamlico Estuarine System, North Carolina, USA. Crabs tethered
in tidal areas swam primarily during ebb tides, both day and night. Swimming frequency increased as embryonic development
progressed and ebb-tide swimming continued after larval release. Swimming frequency varied among habitats with the highest
swimming frequency in the known migratory corridor. Swimming did not occur in the non-tidal habitat. Differences in swimming
frequency among sites are hypothesized to be responses to environmental cues, including flow regime. Some habitats serve as
migratory corridors while others serve as foraging stopovers. These areas are likely defined by a combination of environmental
cues including flow regime. |
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