LOS ANGELES – Carnival Corp., the cruise operator beset by mishaps at sea this year, said Tuesday that Micky Arison will step down as chief executive officer after 34 years while remaining chairman. The shares rose.

The 63-year-old Arison, Carnival’s largest shareholder, will hand the job on July 3 to Arnold W. Donald, a director for 12 years, Miami-based Carnival said in a statement. Arison, son of founder Ted Arison, said he suggested splitting the chairman and CEO roles to align the world’s largest cruise operator with best practices. The company didn’t conduct an outside search, he said on a conference call.

Arison steps aside after crises that generated cable-news coverage and forced price cuts to fill Carnival berths. An engine-room fire on the Triumph ship in February left 3,100 passengers stranded at sea for days with limited food and toilet service. At least two other Carnival vessels were involved in incidents, leading to canceled voyages and customer refunds.

“I view my role as doing whatever Arnold needs me to do,” Arison said on a conference call with investors. “It’s really going to be a collaborative thing between me and Arnold to decide what are the best uses of my time.”

Donald, 58, founded and led Merisant, a company whose products include tabletop sweetener brands Equal and Canderel.

He held senior management roles at Monsanto Co. over more than 20 years, including president of the consumer and nutrition unit and president of its agricultural division.

The change is likely to be well-received by investors, said Steven Wieczynski, an analyst with Stifel Nicolaus & Co., in a report to clients, citing the benefits of fresh perspectives on the company’s practices and processes.