expanded again, once again becoming prominent during the reign of the Bourbons in the 18th century. The Spanish trade of goods was sometimes threatened by its colonial rivals, who tried to seize islands as bases along the Spanish Main and in the Spanish West Indies. However, the Atlantic trade was largely unharmed. The English acquired small islands like St Kitts in 1624; expelled in 1629, they returned in 1639 and seized Jamaica in 1655. French pirates established themselves in Saint-Domingue in 1625, were expelled, only to return later, and the Dutch occupied Curaçao in 1634. Other losses to foreign powers came later. In 1713 as part of the Treaty of Utrecht after the War of the Spanish Succession, the Spanish crown was forced to make concessions which included trading privileges for England that violated the previous Spanish monopoly on legal trade to its colonial holdings. In 1739 during the War of Jenkin's Ear, the British admirals Francis Hosier and later Edward Vernon blockaded Portobello in an attempt to prevent the return sailing of the treasure fleet. In 1741 Vernon's campaign against Cartagena de Indias ended in defeat, with high losses of men and ships. Spain dealt with the temporary British seizures of Havana and Manila (1762–4), during the Seven Years' War, by using a larger number of smaller fleets visiting a greater variety of ports. The end of the War of the Spanish Succession in 1713 marked the beginning of the rule of the Bourbon dynasty over the Spanish Empire, which brought with it the Bourbon Reforms. These reforms, designed to halt Spain's decline and increase tax revenue, resulted in a series of changes to the fleet system throughout the 18th century. Philip V began the reforms by sending investigators to report on conditions in Spanish America, who brought back evidence of fraud. He and following Bourbon kings, notably including Charles III, would make a concerted effort to centralize the administration of Spanish America and more efficiently tax profits from overseas trade. One of these reforms was the granting of trading monopolies for certain regions to trading companies ran by peninsulares, such as the Guipuzcoan Company. Another involved the increased use of registered ships, or navíos de registro, traveling solo outside the fleet system to transport goods. These reforms gradually decreased reliance on the escorted convoys of the fleet system. In the 1780s, Spain opened its colonies to freer trade.