No person shall take or gather for commercial purposes oysters, clams, mussels or other molluscan shellfish from any natural shellfish bed in the state in any boat or vessel unless it is licensed and numbered in the manner provided in this section. Any person desiring to use any boat or vessel for such purpose may make written application to the Commissioner of Agriculture, stating the name, owner, rig, general description and tonnage of such boat or vessel and the place where it is owned, and the commissioner shall issue to the owner of such boat or vessel a license to take and gather for commercial purposes oysters, clams, mussels or other molluscan shellfish from the natural shellfish beds in the state for the term expiring on the next succeeding twentieth day of July, unless sooner revoked, upon the payment of thirty dollars; provided, before such license is granted, the owner or master shall prove to the satisfaction of the commissioner that such boat or vessel may legally be used on work on the public beds of the state and that the dredges and other contrivances do not weigh more than thirty pounds. Each boat or vessel so licensed shall, while at work upon any of the natural shellfish beds of the state, display the number of such license in black figures not less than one foot in length. No such license may be transferred. The sale of any boat so licensed shall operate as a forfeiture and revocation of the license, and the license certificate shall be surrendered to the commissioner.