is one piece episode 761 filler?

In Duke Inuarashi's sanatorium, Chopper continues telling his crew about the Curly Hat Pirates' arrival on Zou 10 days ago, saying that he, Sanji, and Caesar Clown departed from Kurau City in order to get away from the gas. They convened inside the nearby forest, and Caesar started giggling with glee that his gas weapon, Koro, was a success.

Chopper and Sanji were shocked and angry that Caesar created the gas used to incapacitate the minks, although Caesar denied any responsibility for the minks' plight, causing Chopper to beat him up.