Median lethal effect of the water soluble fraction (WSF) of crude oil  on the survival of the fingerlings of mullets (Liza carinata) was investigated under laboratory conditions for 96 hours. The tested concentrations of WSF of crude oil were (2.5, 5, 10, 15, 20, 30, 40 and 50 %), which correspond to 0.195, 0.39, 0.78, 1.17, 1.56, 2.34, 3.12 and 3.9 ppm of total petroleum hydrocarbons content (TPH), respectively of the test water. The study was prepared in two groups (A and B). No mortality was recorded in 2.5-10 % of toxicant, while 12.5 % mortality was recorded in the 15 % of the toxicant. In 20 % of toxicant 37.5 % mortality was recorded, while in 30 % of toxicant, 50 % mortality was recorded and 87.5 % mortality was recorded in the 40 % of toxicant. 100 % mortality was recorded in 50 % of toxicant at 96 hours.  The 96 hours LC50 for both batches was 27.81 % (2.17 ppm). It was observed that mortality was concentration-dependent: the higher the concentration, the higher the mortality. However, it was observed that the field concentration of TPH ranged between (0.009-0.39 ppm) from (0.5-3km) near petroleum refineries to end point of the offshore. This range of TPH in the field studied doesn't reach to the range of lethal concentration, but still at sub lethal concentration.