Effect of Short-Term Stress and Interaction of Salinity and Ammonia-N Levels, Associated With Food Deprivation on Fatty Acid Profile and Body Composition in Nile Tilapia (Oreochromis niloticus).

High levels of nitrogen compounds can lead to acute toxicity in aquatic organisms. Ammonia, a by-product of protein breakdown, is the most prevalent contaminant in freshwater environments. Increasing salinity in water sources can cause fluctuations in salinity levels within breeding ponds. The interaction of these elements can occur in breeding ponds, significantly impacting the physiology and quality of the aquatic products. The purpose of this study was to examine the relationship between salinity and ammonia-N stress and their effects on the quality and fatty acid profile of tilapia fish (Oreochromis niloticus). The fish were divided into 12 distinct treatment groups, each characterized by varying salinity levels (0, 4, 8, and 12 ppt) and different concentrations of ammonia-N (0, 50% of 50% lethal concentration [LC₅₀]-96 h, and 30% of LC₅₀-96 h) arranged in a factorial design. The calculated LC₅₀-96 h for ammonia-N was 0.86 mg/L. Significant increases were observed in cortisol and glucose levels associated with various salinity treatments and ammonia levels. The levels of carcass protein in the salinity treatments (4, 8, and 12 ppt) did not show any significant differences when compared to the control treatment. However, the protein percentage at 50% of LC₅₀-96 h of ammonia-N was lower than that of the control treatment. In salinity treatments and ammonia levels (50% and 30% of LC₅₀-96 h of ammonia-N), a significant increase in the percentage of lipid, highly unsaturated fatty acids (HUFA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) was observed. To draw the conclusion, our assessment indicates that a salinity concentration of 8 ppt over a 96-h period without feeding has produced positive effects on the quality of tilapia carcasses.