Effect of Some Environmental Factors on the Food and Feeding Habits of the Cichlid Fish, Tilapia zillii, Inhabiting Lake Qarun, Egypt.

Abstract

The present work aims to study the effect of the environmental factors (temperature, salinity and PH) on the food and feeding habits of Tilapia zilliicaughted from Lake Qarun. A total of 126 specimens of T. zillii were collected seasonally from the different localities of Lake Qarun, during the period from June, 2014 to July, 2015. Results showed that, the highest value of surface water temperature was recorded at Village 8 Station during summer (32.67±2.31 oC) and the lowest (16.93±1.79 oC) at Nema Island Station during winter. The maximum value of water salinity was recorded at Village 8 Station during summer (40.10±3.46 ‰) and autumn (40.47±2.73 ‰) and the minimum value (29.17±3.52 ‰) was observed at Kahk Village Station during winter. The highest values of hydrogen ion concentrations were recorded at Village 8 Station during summer (8.67±0.15) and autumn (8.76±0.02) and the lowest values were detected at Ezbet Abd El-Alim Station during spring (7.96±0.09) and winter (7.96±0.12). The maximum values of feeding activity were recorded during autumn and summer and the minimum activity was observed during spring. The feeding activity is relatively larger in the younger fish than in the older one; being 41.63% in the former and 25.60% in the latter. Results showed that, the fish is mainly omnivorous and consumed a wide range of animal and plant foods. The plant food includes plant tissue, algae and diatoms while, the major animal food includes molluscs, polychaets, insects, pisces, nematods, crustaceans, Protozoa, Foraminifera and Rotifera. The relative amount of plant food increases with the increasing length of the fish. However, the relative amount of animal food and sand granules decreases with the increasing length of this fish.