Excessive fishing (overfishing) is one of the most important problems facing Lake Mariout, due to its negative impact on the quantity of fish production in the coming seasons, and the lake also faces the causes that led to a decrease in its area from 204 thousand feddans in 1798 to 17 thousand tons in general. The research problem is represented in the fluctuation in the total fish production of the lake and the fluctuation of the main culture production (tilapia) from it to the total fish production in them from 61.38% as a maximum in 2001 to 52.38% as a minimum in 2000. The research aims mainly to identify the effect of excessive fishing on the sustainable use of fishery resources in the Egyptian Lake Mariout. Surplus production models It was found from the estimated results that there is wasteful use of fishing boats in the lake by 273 boats, or about 34% of the maximum number of boats in the lake, as the actual fishing effort exceeded the fishing effort achieved for the maximum sustainable yield, which indicates. The study recommends the continuous review of the maximum permissible number of fishing boats operating in the lake according to technical and economic principles, in order to ensure sustainable use of the materials in the lake, while studying the allocation of fishing boats according to the fishing effort and including them with permits for fishing, in cooperation between the lake administration, fish cooperatives and elders of fishermen.