Spending related to cruises run by Carnival Corp., Royal Caribbean Cruises Ltd. and other lines grew at the slowest pace in at least six years as fewer new ships were launched.Cruise ships traveling to and from US ports and their passengers pumped $32.4 billion into the US economy, a 7.9 percent increase, the International Council of Cruise Lines said in a report released last week, according to a report on Bloomberg. Passengers traveling from US ports rose 6.3 percent to 8.6 million, less than half the rate of growth in 2004. Four new cruise ships were introduced last year and four were taken out of service, leaving the North American fleet unchanged at 192 ships, the trade association said. Six new ships are scheduled to launch in 2006, ICCL said.