Natural Food of the Herbivorous Rabbitfish (Siganus spp.) in Northern Red Sea

The contents of stomach and intestines of specimens of Siganus rivulatus, S. luridus and S. argenteus from the Gulf of Elat were analysed. The percentage of each algal and seagrass species in the diet of the fish was determined. The diet of Siganus spp. was more diverse in the southern part of the Gulf than in the northern one. Near Elat the fish diet reflected the pollution-affected vegetation of the region. S. luridus grazed chiefly brown algae, whereas S. rivulatus and S. argenteus grazed substantial amounts of red and green algae as well. The composition of the diet in two stations was compared to that of the vegetation in order to determine the possible preferences of the fishes. A few red algae, e. g, Champia irregularis were selected by all the three Siganus spp. S. luridus selected Sargassum spp., Lobophora variegata and Cystoseira myrica, which were avoided by S. rivulatus and 5. argenteus. Galaxaura spp, and Halophila stipulacea were selected by S. argenteus, whereas they were avoided by the other siganids.