The Barbary pirates preyed on Christian and other non-Islamic shipping in the western Mediterranean Sea. The pirates often took the passengers and crew on the ships and sold them or used them as slaves. They also did a brisk business in ransoming some of the captives. According to Robert Davis, from the 16th to 19th century, pirates captured 1 million to 1.25 million Europeans as slaves. They often made raids, called Razzias, on European coastal towns to capture Christian slaves to sell at slave markets in North Africa and other parts of the Ottoman Empire. In 1544, for example, Hayreddin Barbarossa captured the island of Ischia, taking 4,000 prisoners, and enslaved some 9,000 inhabitants of Lipari, almost the entire population. In 1551, the Ottoman governor of Algiers, Turgut Reis, enslaved the entire population of the Maltese island of Gozo. Barbary pirates often attacked the Balearic Islands. The threat was so severe that residents abandoned the island of Formentera. The introduction of broad-sail ships from the beginning of the 17th century allowed them to branch out into the Atlantic.