Before today, I knew of only one other celebration centered on a fish. During the Walleye Drop on New Year’s Eve in Port Clinton, Ohio, townsfolk drop a walleye. Not a real walleye–one made out of some sort of fiberglass material. Here’s another case of fish frivolity. This Mad Culture video depicts the Burial of the Sardine in Madrid. The celebration, attended by folks of all ages, is connected to the end of Mardi Gras. The mood is fun and festive complete with people dressed in costumes, some carrying images of sardines.
The sardine burying tradition, according to what I found out here, came about in 19th century when some students in Madrid wanted to recreate a pagan holiday connected to the allegorical characters Don Carnal and Doña Cuaresma. The symbolism has something to do with carnal pleasures over moderation. The festival has since spread throughout Spain, and does indeed involve burying a sardine. The video explains it all.