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 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.”