Shares of Rockhopper Exploration plc (LON:RKH – Get Free Report) were down 2.5% during mid-day trading on Monday . The stock traded as low as GBX 13.60 ($0.18) and last traded at GBX 13.90 ($0.18). Approximately 1,533,047 shares traded hands during mid-day trading, an increase of 100% from the…