If a handler markets 50 percent or more of the volume of the navel oranges in the preceding marketing season, as annually determined by the director, the handler is entitled to nominate and elect two handler members. All other handlers subject to this chapter shall nominate and elect two handler members. Any handler with two handler members on the commission, who later is not entitled to elect two handler members, shall remove one of its two members and the member’s alternate in a manner prescribed by the commission. The vacancy shall be filled in accordance with Section 73112.