A comparative study of fish production from Lake Manzalah before and during the cleansing and development operations based on surplus production modeling approach

 Lakes fisheries play an important role in the Egyptian economy and food security. In the ’80s, they provided more than 50% of harvested fish in Egypt, but now their contribution to Egyptian fish production seriously decreased to less than 11% (2015-2020). Manzalah Lake is the largest natural lake and the most productive in Egypt, yielding annually up to 65 thousand tons. The catch is composed of a variety of marine and freshwater fish species from which the cichlid species, catfishes, and grey mullet are the most common species. Lake Manzalah faced many challenges that resulted in serious changes in its water quality and its fish production as well as the catch composition. A great development project for the Egyptian lakes was established ten years ago after the political leadership program “Rehabilitation of Egyptian Lakes”. The restoration of lake Manzalah started in 2017 and was completed by June 2022. The present study evaluated the fishery status of lake Manzalah before and after the development project. The estimated MSY using the logistic model of Schaefer was 69841.2 tons for the period 2000-2016,  which is not significantly different from the average yield during 2017-2020 (72057.5 tons). The cost-benefit analysis showed that if the scientific regulatory measures were taken into consideration, millions of pounds spent in some cleaning and development steps in the lake can be saved.