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202 Shnoudy A. Bakhoum

202 Shnoudy A. Bakhoum and Samir. N. Faltashigh followed by aquatic insects and crustaceans. According toHickley and Bailey (1987), B. bajed is described as macro-predator inRiver Nile (southern Sudan), its diet consists mainly of fish prey,aquatic insects, organic detritus and aquatic higher plants.The seasonality associated with feeding in the present studyindicated that the maximum degree of feeding intensity was in spring,while the lowest one was in winter. The seasonal variations in feedingintensity may be attributed to the spawning activities, where thephysical space in the body cavity available for the stomach at thespawning period was small, beside the effect of optimum temperatureon metabolic rate or food availability (Kuo and Tanaka, 1984;Nwadiaro and Okorie, 1987). Khallaf et ah (1991) reported that B.bajed is multiple spawner as an environmental adaptation to ensurefavourable conditions for the offspring. This finding excludes the roleof reproductive activities on feeding intensity. However, The declinedfeeding intensity in winter during the present study agrees with thatreported by Hashem (1981).Seasonal variations in diet composition of B. bajed revealedthat fish prey was the main food item eaten through the whole yearexcept in spring, which represents the second important food item aftercrustaceans. This finding accords with Hashem (1981), who showedthat crustaceans appeared most frequently and represented moreabundant food items during spring, while the fish prey was observed ina high percentage during winter months in the fish diet. The seasonalvariability in the diet composition of this species corresponds to theabundance of these food items in the habitat, which appeared to beinfluenced by water temperature and other environmental conditions.This agrees with Gharib, (!991) who stated that flourishing ofcrustaceans in El-Nozha Hydrodrome occurred in spring.Variation in abundance of food species with fish size for Bagrusbajed indicated that the increase in the length range resulted anincrease in the percentage offish prey in the diet of this species. Thiscoincided well with the finding of Bishai (1970) for B. bajed in Sudanand Hashem (1981) on the same species in Nozha Hydrodrome.The diversity in the diet of 5. bajed, which comprised low valuesin spring increasing in autumn and winter to reach the maximum valuein summer may by attributed to the wide spectrum of food items insummer in the habitat.Computed selectivity coefficient of the fish prey groups in thestomach contents of B. bajed showed that Clarias .gariepinus and

FOOD AND FEEDING HABITS 203OF BAGRUSBAJAD IN ALEXANDRIA, EGYPTmullets were positively selected, while cichlid species were notprefered food items for this species. The preference ability of B. bajedto these species plays an important role in species composition of thecatch in the examined area. Factors that influence food selectivity ofpredators are the size and morphology of the food organisms (Bentzenand McPhaii, 1984).ACKNOWLEDGEMENTThe authors wish to express their sincere thanks to Prof. Dr A.Alsayes head of fishery branch, N.LO.F., for his support and valuableadvice. Also they extend their gratitude to all the scientific staff of theprogram for environmental and fishery investigations of the El-NozhaHydrodrome near Alexandria, for their kind help in collecting thepresent material.REFERENCESBentzen, D. and McPhaii, J. D. (1984). Ecology and evolution ofsympatric sticklebacks (Gasterosteus): specialization foralternative trophic niches in the Enos Lake species pair.,Can. J.'Zool., 62: 2280-2286.Bishai, R. M. (1970). Studies on the biology of family Bagrid(pisces) in the Sudan. Ph. D. Thesis, Fac. Sci M Cairo Univ.Cortes, E. ; Manire, C. A. and Heuter, R. E. (1996). Diet, feedinghabits, and diet chronology of the bonnethead shark,Sphyrna tiburo: in southwest Florida, Bull., Mar. StiL, 58(2): 353-367.Crow, M.E. (1982). Some statistical techniques for analysing thestomach contents of fish .In fish food habits studies.Proceedings of the 3 rd Pacific Northwest' technicalworkshop G. M. Cailliet and.. G.. ; A>. Simensted(eds).Washington Sea Grant publication. Washington univ.Seattle, Wash: pp.8-15.GAFRD, (-2000). General Authority for fish resources development,data on fish Production in Egypt, Ministry of Agriculture.Cairo., 207pp.

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