David F. Smith, executive chairman of National Fuel Gas Co., is retiring effective April 1. He would continue to serve as chairman of the board. Smith joined National Fuel in 1978 and was CEO from February 2008 until March. Elected to the board in 2007 and named chairman in 2010, Smith during his tenure served as president of National Fuel Gas Supply Corp., National Fuel Gas Distribution Corp., Empire Pipeline Inc. and National Fuel Resources Inc. “During his five years as CEO, Dave established the current course of the company, focusing attention and significant resources on development in the Marcellus Shale as Seneca Resources Corp.'s total production nearly tripled and the company’s pipeline business commenced a historic, transformational realignment,” said CEO Ron Tanski. Seneca is the exploration and production (E&P) arm of the company. The integrated Williamsville, NY-based operator has $6.2 billion in assets in E&P, gathering, utility, energy marketing, and pipeline and storage.