is one piece episode 524 filler?

The episode opens with the Caribou pirates attack Straw Hats. As the bubbles of the two ships come close Caribou orders his crew to rush on Thousand Sunny.

Caribou manages to get on Thousand Sunny, but the rest of his crew is pulled away by Momoo who runs away when he recognizes Nami, Sanji, and Luffy. When Caribou realizes that he is alone against the Straw Hats he begs them not to throw him into the sea, and finds excuses so as to let him live.