Section 2. There shall be two commissioners of pilots for district one and one deputy commissioner of pilots for each of the other three districts. On or before December first in any year when their terms of office expire, their successors shall be appointed by the governor, with the advice and consent of the council, for terms of three years. A deputy commissioner of pilots for any district shall be a resident of a town having a landing place accessible to vessels from the sea situated within that district. In this chapter, the word ''commissioners'' shall be held to mean, as to district one, the commissioners of pilots for said district and, as to each other district mentioned in section one, the deputy commissioner of pilots for such district. They shall have experience in maritime and nautical affairs. Appointments of commissioners for district one shall be made upon the recommendation of the trustees of the Boston Marine Society provided such recommendation is made. Appointments of commissioners for districts other than district one may be made upon the recommendation of said trustees. No commissioner for any district shall be such a trustee.