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Study shows no post-spill crab decrease

August 8, 2013

Arthur Nead
Phone: 504-247-1443
anead@tulane.edu

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Tulane blue crab researchers (from left) Susan Chiasson, Caz Taylor, Sarah Giltz and Joanna Gyory. Photo: Paula Burch-Celentano.

When researchers from Tulane and the University of Louisiana-Lafayette began a study of blue crabs in the Gulf of Mexico after the Deepwater Horizon oil spill, they expected a big kill-off.  However, their investigations have not indicated any obvious or dramatic mortality rates. The ongoing study is funded by the BP/Gulf of Mexico Research Initiative.

Six months before the spill, Caz Taylor, assistant professor of Ecology and Evolutionary Biology and co-principal investigator of the study, was already researching crab movements along the coast.
 
For months her team collected samples of megalopae, the secondary stage in a crab's development from larvae to adult. Blue crabs live near the shore for most of their lives, but at spawning time, the females swim out into the Gulf. Their eggs hatch into tiny larvae that drift with the currents. Some reach shore and develop into adult crabs.

“The spill began at the peak of the spawning season, and the Deepwater Horizon rig was smack in the middle of my study area,” says Taylor. “My first thought was that everything would die, but as far as we can tell, that didn’t happen.”

With the spill, her investigation shifted focus and expanded to seven sites from Galveston to Appalachicola from mid-May to the end of October, 2010.

“We certainly didn’t get zero crabs in any places, and in some places we collected tens of thousands of megalopae,” Taylor says.

Taylor and her colleagues are trying to determine why the crab population seems unaffected by the spill. Among the causes they are considering is that the closure of some fishing areas for several months gave crab numbers an opportunity to increase, and another is that larvae at the spill site may have been killed but were replaced by larvae drifting from other areas of the Gulf.

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