Effect of Reused Water on Atlantic Salmon

Abstract

Atlantic salmon (Salmo salar) fingerlings were reared in water passing successively through a series of six troughs for 110 d. Fish loading per trough was based on a flow index (a ratio of fish weight to fish length and water flow) of 36.4; thus the cumulative index was 218.4 at the sixth water use. Two indicators of water quality were measured after each water use; mean dissolved oxygen concentration decreased from 7.2 mg/L after the first water use to 3.3 mg/L after the sixth use, and mean total ammonia concentration increased from 0.09 to 0.63 mg/L. Growth rate began to decline at the third water use, when dissolved oxygen averaged 4.9 mg/L and total ammonia averaged 0.40 mg/L.