The present study was focused on assessing the effect of diets formulated with different sources and levels of protein on the production response of white leg shrimp Penaeus vannamei farmed at low salinity (3 g L-1). The protein sources were: soy meal (SM) and fish meal (FM), included at three levels: low (22-25%), medium (32-35%), and high (41-45%). A bioassay of 49 days was done in experimental tanks of 100 L (three tanks per treatment). Juvenile P. vannamei having a mean weight of 1.41 ± 0.30 g were stocked at a density of 100 ind m-3. Shrimp fed diets formulated with FM recorded significantly higher weight gain, specific growth rate (SGR), and protein assimilation efficiency rate (PER). Additionally, it showed a higher concentration of essential amino acids like methionine and threonine, and higher ash, calcium, iodine, phosphorous, and sodium content, which could favor the growth and survival of shrimp. Regression analysis showed that the optimum protein levels for diets formulated with SM and FM were 34.8 and 29.3%, respectively. These findings may help shrimp farmers to implement better feeding strategies for P. vannamei farmed at low salinity and on the use of alternative ingredients to substitute fish meal in the formulated feed.The present study was focused on assessing the effect of diets formulated with different sources and levels of protein on the production response of white leg shrimp farmed at low salinity. The protein sources were: soy meal (SM) and fish meal (FM), included at three levels: low (22-25 %), medium (32-35 %) and high (41-45 %). A bioassay of 49 days was done in experimental tanks of 100 L (three tanks per treatment). Juvenile L. vannamei having a mean weight of 1.41 ± 0.30 g were stocked at a density of 100 organisms/m3. Shrimp fed diets formulated with FM recorded significantly higher weight gain, specific growth rate (SGR), and protein assimilation efficiency  rate (PER), and additionally showed a higher concentration of essential amino acids as methionine and threonine, and a  higher ash, calcium, iodide, phosphorous and sodium content, which could favored growth and survival of shrimp. Regression analysis showed that the optimum levels of protein for diets formulated with SM and FM were 34.8% and 29.3%, respectively. These findings may help shrimp farmers to implement better feeding strategies for L, vannamei farmed at low salinity and on the use of alternative ingredients to substitute fish meal in the formulated feed.