This study was conducted in Wadi El-Gemal using visual census technique in order to study the composition of the fish community in the area and to evaluate the effect of the flooding drain on the abundance and diversity of reef fishes. The area in front of the flooding drain was divided into three transects according to their proximity to the drain. Each transect was divided into three zones; reef flat, reef edge and reef slope and fishes were counted at each zone. A total of 4388 fish constituting 94 species in 23 families of coral reef fish were recorded. The highest number of species was recorded in the reef slope of transect two (85), while the lowest was present at the reef flat (11). The highest number of individuals was recorded in the reef slope, where 1002 fish were counted, while the lowest number was in the first
transect (86). There were no great seasonal variations in diversity but slight differences were noted in abundance of fishes. The highest diversity was observed in the fall with 88 species and the richness was 11.9 while the lowest was in winter with 82 species and the richness was 10.7. Number of species as well as number of fish
increases as the distance from the mouth of the valley increases