Any person who shall unlawfully or intentionally injure, molest, or destroy any of said lines, posts, piers or abutments, or the materials or property belonging thereto, shall, on conviction thereof, be deemed guilty of a misdemeanor, and be punished by a fine not exceeding 500 dollars, or imprisonment in the county jail, not exceeding 1 year, or both, at the discretion of the court before which the conviction shall be had.