The big cruise lines have been steadily filling their rapidly expanding fleets with passengers looking to escape an especially harsh North American winter, but as they get ready to release quarterly results, Wall Street is worried that ticket prices may not be high enough. Analysts are expecting profit declines for the winter quarter from the top three cruise lines, starting with industry leader Carnival Corp., which plans to release its fiscal first-quarter results on Wednesday (March 21, 2001). Cruise stocks, including those of Royal Caribbean, the world's No. 2 operator, and Britain's P&O Princess Cruises, which ranks third, have in recent weeks given up much of their bounce back gains after a sustained decline last year.