It shall be unlawful for any person, his agent, servant or employee in charge of or having custody of any vessel entering or while within any harbor in this State to discharge or permit to be discharged from any such vessel any seepage or refuse of fuel oil or any other oil product. Any violation of this section shall be a misdemeanor and upon conviction thereof shall be subject to a fine not exceeding five hundred dollars. If such fine is not paid it shall be a lien on the vessel over which such person had control prior to all other liens except State taxes and shall be enforceable as other liens are by the laws of this State. The port commissioner or other officer or person in charge of or having supervision over vessels entering the ports of this State shall see that the provisions of this section are enforced.