A comparative study of the length-weight equation and the condition factor of Tilapia zillii from Lake Mariut,Egypt

The length-weight relationship of Tilapia zillii Gerv., seasonally collected from Lake Mariut (a brackish-water lake), Egypt, has been studied. It was found that mature fishes are fatter than spent individuals, and that this mainly affects the exponent n (W=a L ⁿ). While the females are nearly of equal fatness to the males, a higher value of the exponent n is recorded for the females; this is due to the higher weight of the gonads. The smaller fish are more fecundite than the larger, elder individuals; this is revealed by comparison of the condition factor K and GSI (gonadosomatic index) for ripo and spent fish, respectively.