The licensees shall, from time to time, during each year stock each such area with 25 pieces of game per 100 acres at their own expense, under supervision of the Department, unless the Department determines that the area is already adequately stocked. The licensees may at any time during the year train their own dogs or the dogs of other persons on such area or permit others so to do under such conditions as are mutually agreed upon. Neither the licensees nor any other person shall, at any time, hunt or trap within the confines of such area, except that the licensees or any person authorized by them may hunt or trap vermin and predators for the purpose of exterminating vermin and predators on such area.