Shanawan drainage canal is one of the many
drainage canals present in Menufiya province, Egypt. It receives sewage water
from Kafr Shanawan drainage canal. Also, it receive illegal run–off from sewage
and wastes besides sewage of Shebeen Al-koom city. This study is aimed to
investigate the frequency of chromosomal damage by using chromosomal
aberrations test of head kidney cells in Oreochromis niloticus and Tilapia
zillii fish. The study was performed on 5 groups of fish, control and four
polluted groups. A and B stations are located before the source of sewage
discharge while C and D  stations are
located after the source of sewage. In each group cytological studies were
performed. Fishes caught from areas before the sources of sewage showing different
types of chromosomal aberrations, including centromeric attenuations, chromatid
breaks, chromatid gabs, chromatid deletion, centric fusion and fragmentation.
The total aberrations were more obvious among the fishes of the areas after the
source of sewage than those of the areas before the source of sewage. It was noted
that O. niloticus is more sensitive to the effect of pollution than T.
zillii. Cytogenetic Studies of the current Work could be used as criteria
for pollution intensity, which can be used to avoid its toxic effect on aquatic
environment