الفهرس يوجد فقط 14 صفحة متاحة للعرض العام
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المستخلص
This study aimed to evaluate some of the processes related to the reproduction and culture of 0 niloticus fish species. Sex reversal of 0 niloticus fry in earthen ponds has been investigated under four different stocking densities for 28 days treatment period. The experiment revealed the possibility of successful sex reversal of 0. niloticus free swimming fry in earthen ponds with highest growth being attained at low density 140 m2, followed by the intermediate density 260 m2, then 350 m2 and finally 520 m* However, the highest male percentage obtained was in the intermediate and high density.
Intersex fish had been observed in variable percentages among different treatments. Paradoxical feminization has been identified as a potential problem during steroid treatment.
On comparing the performance of sex reversal in earthen ponds to sex reversal in cement ponds; although we could not make a statistical comparison, it was clear that the survival rate and final body weight being attained in earthen pond was better than those recorded in cement ponds.
Residues of MT in 0 niloticus tissues and in the treatment environment (water & soil) were estimated. MT levels in muscular tissue were 490.67, 430.67 and 150.67 ng g’ after 0, 14, and 21 days of cessation of MT treatment respectively, however, 69 days later (i.e., three months after cessation of treatment) the levels detected were declined (44 ng g’) to reach a level about 11 times less than the levels detected just after cessation of treatment. Similarly MT levels in whole fish tissue were 158.67, 152 and 134.33 ng g’ after 0, 14, and 21 days of cessation of MT treatment respectively; however, 69 days later (i.e., three months after cessation of treatment) the levels detected were declined (63.47 ng gj to reach a level about two times and half less than the levels detected just after cessation of treatment. Such levels were significantly lower than the MT level (385.07 ng g’) detected in the whole fish tissue of the control non MT-treated fish.
Concerning MT levels in pond water; it was high (734 ng m1’) after 14 days of MT-treatment cessation, and then decreased to about 84.16 ng ml 90 days after MTtreatment cessation of. On the other hand, a concentration (126.4 ng mr’) was detected on the non MT-treated pond water.
Higher levels of MT (mean = 1368 ng g’) was detected in soil samples collected 14 days after cessation of MT treatment, thereafter MT levels in soil were 1220.67,
814.67, 593.33 and 307.73 ng g’ 21, 30, 60 and 90 days after cessation of treatment respectively.
The genotoxic effect of MT administration with respect to Micronucleus formation was tested in two age groups (45 and 117 day after MT-food cessation) of