Investigation of the Effects of Salinity and Dietary Protein Level on Growth and Survival of Pacific White Shrimp, Litopenaeus vannamei

It is presumed that in hypo- and hypersaline environments, shrimp's requirements for some specific nutrients, such as protein, may differ from those known in the marine habitat; however, few investigations have been conducted in this area of study. In the present investigation, the effects of salinity and dietary protein level on the biological performance, tissue protein, and water content of Pacific white shrimp, Litopenaeus vannamei, were evaluated. In a 3 x 4 factorial experiment, juvenile shrimp with an average initial weight of 0.36 ± 0.02 g were exposed for 32 d to salinities of 2, 35, and 50 ppt and fed experimental diets with crude protein contents of 25, 30, 35, and 40%. A significant effect of salinity on growth of shrimp was detected, with the growth responses (final weight, weight gain) ranked in the order 2 ppt (3.87, 3.50 g) > 35 ppt (3.40, 3.04 g) > 50 ppt (2.84, 2.47 g). No effects of dietary protein level or an interaction between salinity and protein on growth of shrimp were observed under the experimental conditions of this study. Percent survival of shrimp fed the highest protein content (40%, survival of 74%) was, however, significantly lower than those of shrimp fed the other feeds (25, 30 and 35% protein, survival of 99, 91, and 94%, respectively), a result likely associated with the concentration of total ammonia nitrogen, which increased significantly at increasing protein levels. Final water content of whole shrimp was significantly lower in animals exposed to 50 ppt (70.8%) than in shrimp held at 2 (73.7%) and 35 ppt (72.3%). No effect of salinity, protein, or their interaction was observed on the protein content of whole shrimp. The results of the present study are in agreement with reports of superior and inferior growth of L. vannamei reared in hypo- and hypersaline environments, respectively, as compared to what is generally observed in seawater.