Europa Cruise Line will make a decision in early January on whether to operate a second one­ day cruise vessel from the St. Petersburg area year­ round after a Mississippi judge ruled that it had illegally operated in Mississippi waters for 10 months.

The two-ship cruise line, which ceased its one­ day operation from Biloxi, Miss., on the 270-passenger EuropaStar in November, will reposition the EuropaStar to John's Pass near St. Petersburg this month to replace the EuropaSun on it's cruise to nowhere operations while the EuropaSun goes into routine drydock.

President Peter Booth said that Europa Cruises currently operates 10 to 12 day and evening cruises a week from John's Pass on the 270-passenger EuropaSun and would stagger the operating times if both vessels eventually operate from John's Pass year-round.

Although Europa Cruises was initially granted permission to operate its casinos on the EuropaStar within Mississippi Sound in December 1987, the U.S. Customs Service discovered that its initial decision permitting the cruises was based on faulty navigational charts and that permission was rescinded last October.

Booth said that the judge's decision to uphold the Customs Service ruling last month made the Biloxi operation too expensive to operate because the EuropaStar was forced to cruise a full three hours before bonded whiskey could be sold and the casino could be opened.

Booth explained that Europa Cruises was forced to extend its daily cruises from six to eight hours on the EuropaStar from Biloxi after the revised Customs Service ruling in October and that the revised schedule was too costly to continue operations. He added that he thought that the St. Petersburg area cruise market would support a second Europa Cruises vessel and that the two ships would operate from the same pier.

It wasn't clear at presstime whether the State of Mississippi might file suit to obtain back taxes that the state attorney general's office said Europa Cruises owed to the state while the EuropaStar was operating in the Mississippi Sound. A spokesman for the office had said that Europa Cruises might be liabile for back taxes over the 10-month period that the EuropaStar operated in what was officially declared as state waters.