The invention relates to a system for controlling feeding of farmed fish living within a restricted volume, such as a sea cage (10), comprising at least one sensor for direct or indirect measurement of changes in dissolved oxygen (DO) in a feeding area of the fish during feeding, and further comprising a controller (4) receiving input from said at least one sensor and providing output to an automated feed providing system for controlling the amount of food provided to the fish, wherein an increased oxygen consumption and a correspondingly decreased amount of DO in said feeding area serves as an indication of fish hunger and an input parameter of the controlling system. The invention also relates to a method for controlling feeding of farmed fish.