Abstract

The maximum age of Sarotherodon galilaeus in Lake Manzala was four years. The Length and weight relationship was expressed as W=0.0132L3.1025. Also, the growth coefficients were L∞ and K, 28.06 cm, 0.45/yr, and -0.1, respectively. Height at first capture was Lc=10.26 cm with corresponding age Tc=0.85 years. This means that the stock of S. galilaeus in Lake Manzala is being overexploited. For management purposes, the exploitation ratio should be reduced from 0.77 to 0.50 (27%) to maintain the reproductive biomass of this species. The study also showed that the total mortality was (Z=3.28/year), natural deaths (M=0.56/year) and fishing mortality (F=1.82 / year) to the utilization rate of E=0.77. The high values of F and E reflect the high level of exploitation of this species in Lake Manzala. So, for management purposes and to maintain the stocks of S. galilaeus, the fishing mortality rate must be reduced by at least 27% from its current level to achieve sustainability for this species.

Keywords: Population dynamics, Mortality rate, Sarotheradon galilaeus, Lake Manzala