No expenditures or disbursements from the income from proceeds derived from the sales of lifetime sportsman licenses to holders under the age of sixteen (16) years shall be made for any purpose and shall become a part of the fund's principal. Income earned after the holder reaches the age of sixteen (16) shall be available for expenditures or disbursements. The wildlife resources agency shall cause deposits of proceeds from the sale of lifetime sportsman licenses to holders under the age of sixteen (16) to be distinguished and shall maintain information as to the ages of license holders to determine the amount of income that remains encumbered by and that is free of this restriction.