Embattled casino operator William J. Yung III has stepped down as chief executive officer of Tropicana Entertainment Holdings LLC, which has filed for bankruptcy. Tropicana owns Casino Aztar in Evansville and 10 other casino properties in Nevada, Mississippi, Louisiana and New Jersey. According to a company statement released Friday, Yung will continue to serve on a new board of directors, but President Scott C. Butera will take over as CEO of the northern Kentucky-based company.