However, manipulation of the photoperiod did not influence the gonadal development, survival or the appearance of deformities in juvenile Nile tilapia. Fish subjected to a photoperiod of 18L:6D and 24L:0D showed the highest levels of performance. The fingerlings subjected to a photoperiod of 12L:12D as well as those under 18L:6D and 24L:0D showed the greatest locomotor activity, whereas those under 6L:18D and 0L:24D showed the lowest activity. Feeding was carried out twice daily for 75 days, with extruded feed containing 40% crude protein. One hundred and sixty fingerlings of tilapia weighing 3.21☐.05 g and measuring 4.35☐.07 cm each were distributed among 20 aquaria of 20 L in a recirculation system with the temperature controlled to 27 ☌, with eight fish per aquarium. A completely randomised design was used, with five treatments (0L:24D, 6L:18D, 12L:12D, 18L:6D and 24L:0D) and four replicates, with the aquarium as the experimental unit.
The objective of this study was to evaluate the effect of photoperiod on locomotor activity, growth and gonadal development in Nile tilapia (Oreochromis niloticus) fingerlings.
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