A newly developed oxygen injection system for cage farms

A system for the injection of pure oxygen in fish cages has been developed. The delivery of oxygen is controlled using a network of oxygen sensors connected to a PLC system to maintain a set point of dissolved oxygen in the cages. Over the last 3 years, the oxygen injection system has been tested and optimised in commercial sized salmon cages at a research centre. At moderate oxygen deficit and temperature levels common in late summer and autumn, the system increases the oxygen concentration towards the set point. Economic appraisal shows that the value of improved growth and feed utilisation was greater than the cost of oxygen used under normal conditions in fjord based salmon cages in Southern Norway. In extremely warm periods, such as those that existed in Norway between August and October 2002, oxygen addition is vital in order to avoid mass mortality.