Feeding habits and trophic levels of cichlid species in tropical reservoir, Lake Nasser, Egypt

Information on fish feeding habits and trophic levels shed light on trophic profiles and energy transfer within the aquatic ecosystem. In this study, tilapias (Oreochromis niloticus, Sarotherodon galilaeus, and Coptodon zillii) samples from commercial fisheries of Lake Nasser were collected during autumn 2015 and spring 2016, and gut contents were examined. Results showed that plant tissue was more frequent in guts of C. zillii, and sand particles and green algae were more frequent in guts of O. niloticus, while diatoms and sand particles were more frequent in S. galilaeus. Moreover, food of plant and animal origins dominated in large-sized O. niloticus except for hydrophytes that dominated in medium-size samples only. The guts of female O. niloticus contained more plant components than the male. In contrast, the guts of female S. galilaeus contained food of animal origin more than male. Food of plant origin increased in the guts of O. niloticus and S. galilaeus in spring, meanwhile, it increased in the guts of C. zillii in autumn. The trophic level ranged from 2.00 to 2.40 for the three species. The results of this study contribute to the understanding of the feeding habits and trophic levels of these economically important species in Lake Nasser.