User blog comment:Ricizubi/Do you believe that the 10th memeber is Shirahoshi? or Jinbei?/@comment-4094276-20110727212636/@comment-1595565-20110727213402

The Blackbeard Pirates seem to make port more often than the Straw Hats, so there is less of a chance that he would get separated when sleeping. The Straw Hats, on the other hand, actually can sleep on their ship, so they would be traveling at night more often. If Shirahoshi falls asleep, she would get separated.