If pressed, I'd say aileron but who knows at this moment? It's about an oxygen-bottle's width - I think the elevator is much larger but when you're walking around it, everything is large! , however, in planform view in the AOM, the elevators are at least 3x the size of the ailerons.
What we can say is, it IS a flight control surface, (but most certainly not part of the horizontal stab box, which is metal, not honeycomb structure).
Yes I think that it is a canoe from a wing (significant only if it confirms the wings were still attached when it hit the water) therefore a much denser debris field.
PJ2, lomapaseo,
With a reasonable degree of certainty I would identify the piece of flight control surface wreckage as being a portion of the wing leading edge that normally lies beneath a leading edge slat. The small notch is the point at which an actuator rod extends through from the slat drive to the slat. In fact, a close look at the photo suggests that a part of the actuator rod is still present within the notch. Notches of this sort do not exist on the alierons, flaps, horizontal stabs or elevators, at least not that I've ever seen.
From the camber and rivet configuration my guess is that this piece came from the upper side fairly close to the wing tip. A bit of supporting evidence for this supposition is the grease mark on the rear portion of the section. This sort of mark is usually found on components nearby lubrication points, in this case probably a slat track that would have been located to one side or the other of the piece recovered.
ELAC