Effect of a Gradual Salinity Increase on Water Quality, Survival and Growth Performance of Hybrid Red Tilapia (Oreochromis mossambicus ×O. niloticus)¹

We studied the effect of increasing salinity with respect to growth performance and water quality of Hybrid Red Tilapia (Oreochromis mossambicus × O. niloticus) (1.29 ± 0.48 g and 4.05 ± 0.48 cm) for 77 days, and we compared the obtained results to freshwater rearing. The results indicate no significant difference in all physico-chemical parameters between both variants, which are within the accepted range for fish growth. Better growth performance regarding weight was observed in freshwater rearing. However, in terms of length, the increasing salinity rearing showed the best growth performance. The survival rate decreased with a salinity increase, unlike freshwater rearing which showed 100%. Hybrid Red Tilapia raised in freshwater revealed isometric growth. However, Hybrid Red Tilapia reared in increasing salinity reported negative allometric growth. A strong positive correlation was observed between salinity and total length and weight, and between total length and total weight, while survival was strongly negatively correlated with salinity and total weight. Positive loadings of salinity, N\({\text{H}}_{4}^{ + }\), total length, and total weight were observed relatively to the factor 1, whereas N\({\text{O}}_{2}^{ - }\) and survival show negative loadings. For the factor 2, the chemical variables (N\({\text{O}}_{2}^{ - }\), P\({\text{O}}_{4}^{{3 - }}\) and N\({\text{H}}_{4}^{ + }\)) were the important variables. Our experiment suggests that Hybrid Red Tilapia can be reared in biotopes that are subject to climate change or that experience a hot and dry climate.