MOBILE – Carnival Corp. will replace its Mobile-based Holiday cruise ship with the larger Fantasy vessel next year, boosting its capacity at the Alabama port by 42 percent.

The announcement Monday came aboard the 2,056-passenger Fantasy, which normally is based in New Orleans, but is operating out of Mobile through Sept. 1 because of an oil spill on the Mississippi River.

Carnival spokesman Terry Thornton said the Fantasy will undergo improvements next month while in dry dock, turning some open decks into water parks with a 300-foot-long spiral slide. The ship will continue cruises from New Orleans in October until its move to Mobile in November 2009.

Thornton said Carnival expects the Fantasy will be based at Mobile for a long time.

The 1,452-passenger Holiday, Carnival’s oldest vessel, will be sent to Spain next year, but will continue to operate from Mobile until its departure on Nov. 2, 2009. The ship will be transferred to Iberocruceros in Spain.

The Holiday has been based at Mobile since 2004 when the city entered the cruise market.

“We knew Mobile would be a great cruise city,” Mobile Mayor Sam Jones said aboard the Fantasy. He said Carnival’s decision to homeport its larger ship in Mobile fulfills that expectation. He also said nothing was asked of the city to win the 70,000-ton Fantasy.

The city has approved spending $3 million to upgrade the cruise terminal to handle a larger vessel and continues to search for a second ship for the city.

Since its arrival, the Holiday on average has sailed full, according to Carnival, and the Fantasy will bring more tourism dollars.

Leon Maisel, president and CEO of the Mobile convention bureau, said the 42 percent increase in capacity could generate $3 million in cruise ship revenue, based on passenger stays and related activity.

With the Fantasy based in Mobile, Carnival expects to carry about 170,000 passengers annually from the port.

Meanwhile, the cruise industry expects to benefit from the rising cost of air travel, Thornton said. He said airlines could cut capacity this fall.

“We’re just watching it close,” he said.

The Fantasy, which has not departed from or arrived in New Orleans since a tanker and barge collision caused an oil spill in the river on July 23, conducts four- and five-day cruises to the west Caribbean.