Whoever, after notice by the owner, occupant or lessee in any of the ways provided in section 7557, trespasses upon any island within salt waters, for the purpose of shooting or hunting thereon, is liable to such owner, occupant or lessee in exemplary damages to an amount not less than $20 nor more than $50, in addition to all actual damage sustained by said owner, occupant or lessee, and shall forfeit to said owner, occupant or lessee $5 for each bird of any kind shot, caught, taken or killed on such island, all to be recovered in a civil action. The possession of guns, decoys or other implements of shooting or hunting shall be presumptive evidence that the purpose of the trespass was shooting or hunting.