The council shall fix the salary of the mayor, which salary for the term commencing January 1, 1976 shall be fixed by council not later than January 15, 1975.
If the salary of the mayor is thereafter to be changed in respect to a succeeding term of office such change shall be made by council not later than the 15th day of January immediately preceding the commencement of a new term of the office of mayor and shall become effective upon the commencement of such term, provided that the salary of the mayor may, with his consent, be decreased during his term of office.