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vol-2“FOOD AND FEEDING HABITS OF SOME EGYPTIAN FISHES IN
LAKE QUARUN.
Part I. Tilapia zillii (Gerv.) C. According to different sexes
Dr. S. A. ABDEL-~IALEK
Lnstituie of Inland Fisheries and Eis]: Culture.
ABSTRACf
The material was collected over a four-months period from December 1969 to March 1970. The data so obtained were analysed by using
the occurrence & the points methods. T. ziUiiofboth sexes feed on plant
material as well as on food of animal origin. The males & females took
about nearly the same food items but with a slight difference in proportion. The percentage of fish with empty alimentary canals decreased
gradually from December 1969 to March 1970. So, in December, 55.6%
&41.7%of the digestive tracts of males & females respectively were found
to be empty; while in March, all the males had food in their alimentary
tracts & 14.5% of the females were with empty digestive tracts_ The
plant components eaten by T. ziUii of both sexes were diatcm.!: (C08-
cinodi8cus sFP., Grammatophora spp., Lycmophora 8FP., Synedra 8pp.,
Oocconeis BFP., Navicula 8pp., Diploneis SFP., Gyr08igma 8pp.,
Nitz8chia sFP.) . Cyanophyta (Microcysli8 Spp., OsciUatoria spp., Lyngbya BpP.) ; Polysiphonia spp. ; Ecsocarpus 8pp. ; higher plant tissue &
plant detritus. Animal organisms including Prorocemrum unicans,
Nereis spp., Ostrccoda, Acartia latisetosa, Gammarus Bpp., water insects,
H ydracarina, Gastropoda, A bra OIXUa, Cardium edule, fish eggs, fish
larvae, fish scales & animal detritus were used as food for Bolti (males
& females). Insignificant quantities of inorganic particles were rarely
seen in the alimentary canals of the females in February 1970 &
March 1970.
It is of interest to mention that during December 1969, January &
February 1970, the plant material, especially PolY8iphonia spp.,
diatoms & Cyanophyta ; were the most important food components for
Bolti of different sexes, while the animal material was the second.
The picture was reversed in March 1970, as it was found that the animal
organisms particularly Nereis spp. &Gammarus spp. made up the principal food items for both males & females, while the plant components
played the second role as food for Bo lti of different sexes.
