Despite economical importance of Lake Qarun fishes, few data are available on the gut content of adult specimens. During this study, 510 alimentary canals of most common fishes in Lake Qarun (150 Tilapia zillii Gerv.; 110 Oreochromis niloticus Linn; 75 Mugil cephalus Linn. and 175 Solea vulgaris Linn.) were examined. T. zillii (Gerv.) are filter feeding fish, it consumes mainly net phytoplankton of Lake Qarun. Approximately Bacillariophyceae and Dinophyceae were dominated the fish diet. These groups constituted more than 85 % of the total phytoplankton crops for all the examined fishes. However, other classes (Chlorophyceae, Cyanophyceae, Euglenophy-ceae and Cryptophyceae) were observed in comparatively few numbers in the guts of the selected fish. Also, diatoms and dinoflagellates are very important food items for Oreochromis niloticus (Linn.), however Cyanophyceae occu-pied the third prominent position as food for such fish. Solea vulgaris (Linn.) preys heavily upon dinoflagellate Prorocentrum micans Ehr. Moreover, this fish showed a special prefere-nce to diatoms species, on the other hand the other classes were completely disappeared. Correspondingly Mugil cephalus (Linn.) has low efficiency in utilization of natural food of algae. Adult mullets may be dependent to a large extent on zooplankton composition. On the basis of frequency occurrence (FO) and average number, most common fishes of Lake Qarun prefer diets diatoms and dinoflagellates. It is very interest to close fishing season and transplant fish fry during the blooming period to enhance phytoplankton grazing by filter feeding fishes.
Lake Qarun, phytoplankton, food and feeding, Tilapia zillii, Oreochromis niloticus, Solea vulgaris, Mugil cephalus