A union representing thousands of Maine’s shipbuilding and paper mill workers now has its sights set on lobstermen. With promises to fight bad legislation and negotiate prices for their catch, union organizers have been recruiting fishermen in some of Maine’s most lobster-dependent communities, including Vinalhaven, Stonington and Jonesport. The union says more than 250 fishermen have signed up for what will be called the IAM Maine Lobstering Union. With low lobster prices and regulatory challenges ahead, fishermen who are joining the International Association of Machinists and Aerospace Workers union say they need to do something to preserve their way of life. But others say the Maryland-based union has the potential to do more harm than good. The Maine Lobstermen’s Association has launched a website raising questions and concerns about it.