A licence under section five of the principal Act authorising the use of a ship or factory for taking whales or for treating whales may be granted for a shorter period than one year, and the fee charged in respect of the grant of such a licence for such a shorter period may be less than that charged in respect of the grant of such a licence for a year; and accordingly the said section shall have effect as if at the end of subsection (3) thereof there were added the following words " or for such shorter " period beginning on the said day as may be specified " in the licence; and subject to the provisions of the last " preceding subsection, different fees may be charged in " respect of the grant of licences for different periods."