Using Salt-Enriched Diets to Reduce Stress in Trout

Chronically stressful conditions in fish culture facilities can lead to outbreaks of disease and reductions in growth and performance. A secondary response to stress in fish is the sudden and significant loss of plasma chloride ions, a condition known as hypochloremia. This loss of plasma chloride has been implicated as a cause of mortality in severely stressed fish. The effect of increased dietary salt on reducing hypochloremia in rainbow trout (Onchorynchus mykiss) subjected to a confinement challenge was investigated. Experimental diets included added NaCl or CaCl2. Trout fed salt-enriched diets suffered less hypochloremia in the early hours or confinement. Trout fed a higher level of NaCl had significantly higher recovery plasma chloride levels post-stress. Salt-enriched diets containing moderate levels of NaCl may offer some benefit in recovering trout that have been exposed to stress.