Lights at night, sailors’ delight. Under a blue, dusky sky on Saturday, a flotilla of more than a dozen private and commercial vessels launched into Casco Bay for the 16th annual Parade of Lights. The boats, adorned with festive strings of Christmas lights and inflatable lawn decorations, circled the mouth of Portland Harbor before forming a line and cruising past the Old Port’s wharves toward the Fore River. The event culminated with a fireworks display launched from a boat motoring slowly past hundreds of brightly lit faces crowded on Maine State Pier. Casco Bay Lines, which operates a fleet of passenger ferries from the pier, launched two boats full of spectators. Tickets were sold out.