Section 15. Such lien shall be dissolved unless the person claiming it within thirty days after the vessel departs from the port at which she was when the debt was contracted, files in the office of the clerk of the city or town where the vessel was at such time, a statement, subscribed and sworn to by him or by a person in his behalf, giving a true account of the demand claimed to be due to him, with all just credits, the name of the person with whom the contract was made, the name of the owner of the vessel, if known, and the name of the vessel or a description thereof sufficient for identification. The statement shall be recorded by such clerk in a book kept by him for that purpose, and the fees therefor shall be as provided by clause (55) of section thirty-four of chapter two hundred and sixty-two.