This study was designed to provide quantitative information about the most important commercial stocks in the River Nile. Due to their economic importance the Nile Tilapia Oreochromis niloticus was the focus of the present study. Production per biomass simulations indicated that the current fishery resources of this species can produce a fish production equivalent to 124% of its biomass on a yearly basis. The current situations of fishing effort in the River Nile is critical as regards to overfishing. The sexually mature fish will decrease to a low level that will cause a breakdown of the propagation
cycle in the River Nile. The analysis of fishery population dynamics of O. niloticus in Cairo sector of the River Nile indicated that the current fishery policy causes a total mortality rate (Z) equivalent to 1.12 y-1 in the catch curve. The yield per recruit for O. niloticus during its life cycle indicated that this species can produce a fish yield equivalent to 2633 kg every 1000 kg biomass at age group 025 year during its life cycle which extends to 4 years. The simulation analysis
revealed that the yield per recruit that could be obtained under the different combinations of fishing effort and mesh sizes is optimal when using a fishing rate (F) of 0.6 and mesh size equivalent to age of first capture (Tc) 1.5 years. The gear selectivity study indicated that the trammel net El-Nakaria is selective to optimal total length 13.42 cm, while the trammel net El-Mohair is most selective to optimal total length 18.79cm.