Increased surgery volume was a major factor behind jumps in operating revenue and operating income for Sarasota County Public Hospital District in fiscal year 2017. But a dip in investments pulled down total income for the year ended Sept. 30 for the district, which operates Sarasota Memorial Health Care System. The system, with a staff of 5,600 and a $394 million total payroll, is among the region’s largest employers, and its $731 million in total operating expenses help support a variety of…