Adriatic Sea (ādrēă´tĬk), arm of the Mediterranean Sea, between Italy and the Balkan Peninsula. It extends c.500 mi (800 km) from the Gulf of Venice, at its head, SE to the Strait of Otranto, which leads to the Ionian Sea. It is from 58 to 140 mi (93–225 km) wide, with a maximum depth of c.4,100 ft (1,250 m). The Po and Adige rivers of Italy are the chief affluents. The Italian coast (west and north) is low; Venice, Ancona, and Bari are the principal ports. Trieste, at the northern end of the sea, was once the chief Adriatic port. Slovenia, Croatia, Montenegro, and Albania border the irregular eastern shore; Rijeka and Split, Croatia, are the main ports. The Croatian coast (see Dalmatia), which is rugged and has many offshore islands and sheltered bays, is a popular tourist resort. Fishing is an important activity in the Adriatic Sea; lobsters, sardines, and tuna are the chief catch.