Abstract
Oreochromis niloticus frys were packed in polyethelene plastic bags 5 litre volume each at 4 densities 25, 50, 75 and 100 frys / package. The frys were three types A) Oreochromis niloticus, B) Androgen sex reversed and C) Genetic monosex, within each density. There were three sizes 200-300 mg, 500-800 mg and 900-1200 mg. The packaged frys were transported shaded from El-Behera to Alexandria about 60 km, then observed for the survival rate, nervous manifestation, biting dead frys and oxygen depletion from each package for four consecutive days.
Oreochromis niloticus exhibited the highest percentages for gasping air and whirling movements than androgen sex reversed and the genetic monosex. On the contrary, androgen sex reversed exhibited the highest percentage of feeding activity and survival rates than others. The large size frys exhibited the highest percentages of gasping air; whirling movement and the lowest biting activity and survival rate. The smallest size exhibited the lowest nervous manifestation and the medium sized frys showed the highest biting rate and survival rate.
Higher densities induced highly significant air gasping and whirling movement and reduced biting activity and survival rate. Moreover, the nervous manifestation increased gradually as the storage period increased to reach the peak at 66 hr of storage then declined again, while, the biting activity showed high rate after 6 hour then declined at a lower level at 12 hours of storage then gradually increased till reach the peak at 66 hours then declined again.
The survival rate declined during the first 24 hours of storage by 0.25 %, increased to 0.5% and 1% during the second day and third days of storage while during the 4th day reduced to 4% during first 6 hours and 6.5% during next 6 hours (84-90 hours of storage).
The oxygen levels were higher in both air and water of androgen sex reversed frys followed by genetic monosex frys then the Oreochromis niloticus. Moreover, the oxygen levels lowered with increase fry size and density. The largest frys packages and higher densities ones had the lowest oxygen content in air and vice versa.
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