Abstract:
The objective of this study was to explore the effect of treatment duration on
ultrasound cum 17ß-methyi testosterone immersion technique of sexually
undifferentiated Nile Tilapia fries to produce all male mono-sex population in 1.5h
and 2.Oh. A 50 fries density of three treatment groups were immersed in one litre of
100 pg/L 17-ß, methyl testosterone hormone solution with and without cavitation
level ultrasound, without hormone immersion ultrasound only along with the
control group of which neither hormone immersed nor ultrasound received in both
treatment duration. Hormone immersion with ultrasound in two hours duration
produced significantly higher effect (p<0.05) on percentage of males 92.02 ± 0.80
(mean ± SD) and the mean survival rate of 83.67±1.53 (mean SD), where as the
1.5h duration produced 83.00±0.68 (mean ± SD) percentage of males. Ultrasound
application alone without hormone solution also, produced higher male percentages
of 81.36±0.65 (mean ± SD) and 79.77±1.34 (mean ± SD) in 1.5h and 2.0h treatment
durations respectively, than the hormone immersion only without receiving
ultrasound application which produced 77.86±1.7 (mean ± SD) and 78.55±0.24
(mean ± SD) male percentage in 1.5h and 2.0h treatment durations respectively. All
treatment groups produced significantly higher (p<0.05) results than the control
group which neither received hormone-immersion nor ultrasound produced 56.59±
2.75 (mean ± SD) and 56.26 ± 0.82(mean ± SD) percentage of males in both 1.5h
and 2.0h treatment durations respectively. This study indicated that 50 fries/L unit
in an ultrasound cum 17- (3, methyl testosterone hormone immersion for 2.Oh
duration would be commercially viable than the previous protocols recommended
and this protocol would be adapted by farmers as an alternative for 2 Id nursery
phase dietary administration of 30mg/kg 17- ß, methyl testosterone.
