is one piece episode 539 filler?

Robin is seen walking through the Sea Forest and eventually finds what she was looking for. Meanwhile, Neptune's army escapes the palace and the Ministers lament on how this has turned out.

The Minister of the Right tells the soldiers to look for the princes and then they'll come back to reclaim the palace. While this is going on, the New Fish-Man Pirates are forcing the citizens of Fish-Man Island to step on a Fumi-e of Otohime's face as loyalty.