Length-Weight Relationship and Condition Factor of Some Fishes from the River Nile in Egypt with Special Reference to Four Tilapia Species

This study has been carried out along the River Nile (river main stream, Rosetta and Damietta branches) in Egypt. Fish Samples of 21 species belonging to 11 families were collected mainly from the catch of three fishing gears and methods, Trammel net, Traps, and Longlines. Total length (cm) and body weight (g) were measured and data were applied to the equation of W= a L^b, for the length-weight relationship and K= 100 × W / L³ for condition factor. Four cichlid species, namely: Oreochromis niloticus, Oreochromis aureus, Tilapia zillii and Sarotherodon galilaeus were investigated in details. T. zillii exhibits isometric growth in both main stream and Damietta branch, where, relative growth coefficient (b) = 3.0266 and 2.9698, respectively. S. galilaeus follows the same pattern in Rosetta branch (b = 3.0154). Generally, allometric growth noticed for the four studied species in the three branches of the River Nile. The value of (K) of different cichlid species was fluctuated during different seasons in the three studied areas of the River Nile. The value of condition factor of the four studied species inversely related to the size of fish. In general, variation in the most studied biological characters of cichlid species in the three studied areas of River Nile was noticed. Allometric growth for the four studied species in the three branches of the river indicating increase of pollution. The present study recommends that these selected sectors need proper management.