Huntington Beach, Calif. — Gregory A. Trojan, chief executive officer of BJ’s Restaurants, Inc., will retire effective September 1, 2021, at which time BJ’s current president and chief financial officer, Gregory S. Levin, will be appointed president and chief executive officer. Trojan is expected to continue to serve on the board of directors following his retirement, and Levin is expected to be appointed to the board. In addition, the company’s vice president of strategy and financial planning and analysis, Thomas A. Houdek, will be appointed senior vice president and chief …