For the holidays this year, SliCE locations throughout Philadelphia will combine a fishy Italian tradition with a cheesier, more circular one to bring us a special holiday pizza.

The restaurant today brings back their "Pizza of the 7 Fishes," a pie that takes its inspiration from la Festa dei Sette Pesci, or the Feast of the Seven Fishes. In keeping with that tradition, the pizza is topped with sautéed clams, mussels, shrimp, tuna, crab meat, anchovies, and sardine (plus mozzarella, lemon, and basil).

Originating in Southern Italy, the Feast of the Seven Fishes takes place on Christmas Eve, and has its roots in the Roman Catholic tradition of abstaining from red meat during the holiday until Christmas Day. Why the tradition focus on seven fishes, however, is somewhat of a mystery — and, to boot, some families serve three, nine, eleven, twelve, or even thirteen fish dishes.

All SliCE locations (Rittenhouse Square, Italian Market, Fishtown, and Washington Township in New Jersey) today will offer free samples of the pizza from 4 p.m. to 7 p.m. Ordinarily, the Pizza of the 7 Fishes runs $19 for a small, and $26 for a large.

SliCE will continue to offer the pizza through Dec. 24. Then, you're out of luck until next year when it comes to this pescatarian pie.