Lake Qarun (21,800 ha) in Fayoum, Egypt is a closed system which originated from a fresh water lake called Mories. After the disconnection of Nile water reaching the lake, the agricultural drainage water of Fayoum province became the only source of water feeding the lake. Consequently, and due to the extensive evaporation, the salinity of lake water has increased progressively. The salinity increase accompanied by the nutrient load in the incoming water has detrimental effects on the species composition of the lake fishery. Frequent fishery surveys indicate the significant contribution of green tilapia, Tilapia zillii in the lake catch. The reason for that is attributed to its high tolerance to salinity compared to other tilapia species such as Nile tilapia (Oreochromis niloticus), blue tilapia (Oreochromis aureus) and tilapia galilaea (Sarotherodon galilaeus) which may exist in the catch but at negligible quantities.
It may be of interest to know that although the displayed tilapia –as shown in thee inserted photo- is usually much smaller than other tilapia species (due to its early maturation), its price is much higher due to its unique taste as well as the egg roes that almost fill the body cavity of females.