The present study is the first concerning commercial trammel net selectivity in  El-Salam Canal. Selection ogives were estimated using Holt's method (1957) for both Oreochromis niloticus and Oreochromis aureus . L₅₀ retention lengths of both species were estimated as 11.1-cm and 11.5-cm corresponding to the inner layer-mesh bar (2.15-cm) for the two species, respectively. With increasing the mesh bar to 2.65cm, L₅₀  increased to reach 14.2 and 13.0cm in respective order for both species. The mean selection length calculated by Holt's method for Oreochromis niloticus increased from 11.97-cm (as opposed to the smaller mesh bar) to 14.76-cm (as opposed to the larger mesh bar). The same trend for O. aureus, the mean selection length increased from 11.64-cm to 14.34-cm in respective order also. Therefore, it's recommended to use a larger inner layer mesh bar length of 3 cm at least to gain extra weight and give more reproduction opportunities.