NORTH HAVEN — The Marlin Firearms Co., one of the town’s top taxpayers, will start to lay off employees in May and will close by June 2011. The gun manufacturer’s employees were told Thursday that the jobs of 265 salaried and hourly workers would be eliminated over 18 months. Marlin traces its history back to 1870. Marlin officials could not be reached for comment, but First Selectman Michael J. Freda heard the news from a company official Thursday evening. Freda said several factors appear to be driving the closure, from the cost of doing business in Connecticut to wage differentials.