Notwithstanding that Part I of the 1894 Act remains in force and that existing registrations of fishing vessels thereunder continue in force after the commencement date to the extent provided by section 13(3) of the principal Act, no transfer of a fishing vessel or share therein, and no mortgage on a fishing vessel, or transfer or discharge of such a mortgage shall, on or after the commencement date, be registered in any register kept under the said Part I, nor shall any entry relating to a fishing vessel be made in any such register except entries made pursuant to section 21 of the said Part I (closure of the register).