Wis. Stat. § 195.16: Pass lists.

Every water carrier shall keep and for 2 years preserve a record of every ticket, pass or mileage book issued to a resident of this state free or for a money consideration less than that charged the general public. Such record shall consist of the name of the recipient, the amount received, and the reason for issuance, and shall be open to inspection by the office upon reasonable notice during such period of 2 years.