Effect of cage size on oxygen levels in Atlantic salmon sea cages: A model study

Abstract

The supply of dissolved oxygen (DO) to salmon in sea cages depends on many interacting factors including biomass density, temperature and current speed. With other factors being equal, hypoxic conditions are more likely to arise in large cages compared to small. In this work, a mathematical model of DO in sea cages is used to analyse the effect of horizontal cage size in particular. It is shown and quantified how the DO level at key locations in the cage depend on cage radius and current speed, and the fraction of the cage volume with hypoxic conditions is estimated as a function of cage radius, current speed and temperature.

The results of this study give new insight into how oxygen conditions are affected when cage size is scaled up or down. Although conditions at actual aquaculture sites are highly variable and complex, the results can help forecast the effect of increasing cage size at existing sites, and can help guide the planning of new production sites with regard to oxygen supply.