Community structure and fish assemblage at Marsa Abu Dabab, Red Sea, Egypt.

The fish assemblages of different habitats at Marsa Abu Dabab (north Marsa Alam, Red Sea) were examined by visual census techniques. Fish communities were estimated for each of the investigated habitats; seagrasses and coral reefs which have divided into three sectors; sector A (at north) and C (at south) represent coral reef habitats, whereas sector B (in the middle) represents seagrass habitat. A total of 172 fish species representing 94 genera were recorded at Marsa Abu Dabab. The coral reef habitat had the highest number of species (162 species), while the seagrass habitat had the lowest (90 species). The highest average abundance was recorded at sector C in the reef wall habitat (1119 fish/1000 m^3), with the lowest value at sector B in the seagrass habitat (240 fish/1000 m^3). Some fish species were restricted to seagrass or coral reefs, while others were widespread along the gradient. Regarding to fish distribution patterns, five families showed increasing in coral reef habitat (Pomacentridae, Labridae, Acanthuridae, Chaetodontidae and Serranidae), while other three families were abundant in seagrass beds (Siganidae, Sparidae and Mullidae). The five families in coral reef habitats showed in high abundance on reef wall (RW) more than reef flat (RF), except Acanthuridae.