Bigger is not always better: how cage size and depth influence dissolved oxygen in salmon farming

Bigger cages potentially allow for increased Atlantic salmon production and higher profitability, but only if water quality remains good. As cage size increases water exchange decreases, which may in turn cause low dissolved oxygen conditions within cages. To test this, PhD student Tina Oldham from the University of Tasmania compared how dissolved oxygen concentrations varied with cage size on a commercial salmon farm during the 2015/16 Australian summer heatwave. Overall, Tina found that dissolved oxygen levels in all tested cages were generally high and suitable for salmon feeding and growth, and lowest oxygen concentrations consistently occurred in the larger cages. Bigger, it turns out, is not always better.