Waterflow requirements for salmonids in single-pass and semi-closed land-based seawater and freshwater systems

Abstract

The first part of the study derives simple mathematical equations from available empirical data relating to the waterflow requirement for salmonids from the initiation of starfeeding in freshwater until slaughtering weight is reached in seawater. Waterflow requirements in both single-pass and semi-closed freshwater and seawater systems are considered when the oxygen level in the inlet water is regulated. The second part shows trends obtained by computer simulation of the derived equations. Waterflow requirements in single-pass systems, after the addition of oxygen, are considered and feeding rate and pH shown to produce significant differences between the waterflow requirements of freshwater and seawater systems when ammonia is regarded as the limiting factor. The relative importance of water temperature, the threshold level of unionized ammonia and salinity are also shown and the influences resulting in minimum flow rates elucidated. Simulations show the value of semi-closed seawater and freshwater systems in further reducing waterflow requirements.