The Movistar rider came charging through, next to the barriers, to edge out Wouter Poels at the end of the 153km stage that began and start in Guenes.
Garmin-Barracuda's Fabian Wegmann was third.
Spain's David De la Fuente (Caja Rural) and Italian Davide Mucelli (Utensilnord) went away after 16km and built up a four minute advantage as they crossed seven climbs, four of which were third category.
But they were caught inside the final 20km and a bunch gallop to the line ensued in the opening stage of the six-day World Tour race.
Levi Leipheimer pulled out of the race due to training accident with a car where he suffered bruising leaving Andreas Kloden, Frank Schleck, Michael Rogers, David Arroyo, Joaquin Rodriguez, Simon Gerrans, Damiano Cunego, Jurgen Van Den Broeck, Robert Gesink, Dan Martin, Samuel Sanchez and Tony Martin as the leading GC contenders.