The Po Delta has been home to eel-marinating factories for centuries. The most important processing center was the Manifattura dei Marinati in Comacchio. The adult eels were caught in barriers called lavorieri, positioned near the outlets to the sea. They were transported to the factory in boats called marotte, which had special systems for changing the water to keep the eels alive.
At the factory the eels were selected, cut, threaded onto iron skewers and cooked over a wooden fire with a dozen fireplaces. Given the very limited fishing period, it was traditional to marinate them in vinegar so that they could keep for longer.
Eels are caught from October to December and are marinated only in winter. Preserved eels kept throughout the year.