The practical work of the present experiments was carried out at the World Fish Center, Abbassa, Abou Hammad, Sharkia, Egypt. The experiment aimed to investigate the effect of spawning month (April and May), dietary protein level (25 or 35%) and protection of spawning tanks (covering or uncovering of the spawning tanks) on fry production and average fry weight of the Nile tilapia. The obtained results can be summarized as follow:-Fry production/tank were found to be 6462 and 19082/tank during the two months April and May, 10719 and 14824/tank for the two dietary protein levels, 25 and 35% and 16428 and 9115 fry/tank for the covered and uncovered tanks, respectively and the differences in fry production due to the effect of spawning month, dietary protein content and tank protection were significant.-Averages of individual fry weight as affected by month, dietary protein levels and pond protection were found to be 0.025 and 0.016 g during the two months April and May, 0.021 and 0.019 g for the two dietary protein levels, 25 and 35% and 0.018 and 0.023 g for the covered and uncovered tanks, respectively. Spawning month and tank protection significantly affected individual fry weight while dietary protein levels had no significant effect on fry weight.-The interaction between the studied factors affected individual fry weight of the Nile tilapia indicated that the highest average individual fry weight was recorded for fish group raised in covered tanks and received the lower protein content during April. On the other hand, the lowest average individual fry weight was recorded for broodfish raised in an uncovered tanks and received the higher protein level (35%) in May.
The present experiment was carried out to investigate the effect of rearing water temperature in combination with or without hormone application on masculinization of newly hatched O. niloticus fry. Nile tilapia fry (0.025 g) were reared in three levels of temperature 25, 30 and 35°C and in each rearing temperature fry were fed diet with or without supplementation of 60 mg 17α-methyltestosterone (MT) for 7, 14, 21 and 28 days. O. niloticus fry fed diet without MT and reared at different water temperature 25, 30 and 35°C significantly increased the male ratio from 48.67 to 48.67 and 65.33% after one week; 48.67 to 64.00 and 72.67% after two weeks; 48.67 to 68.67 and 77.33% after three weeks and 48.67 to 80.67 and 84.00% after four weeks, respectively. While fry fed diet supplemented with MT with increasing rearing water temperature from 25 to 30 or 35 °C significantly increased male percentage from 58.00 to 84.67 and 86.00% after one week; 67.66 to 93.33 and 96.67% after two weeks; 79.00 to 97.33 and 98.67% after three weeks and 85.67 to 98.00 and 99.33% after four weeks. Mortality rate for O. niloticus fry reared at different water temperature 25, 30 and fed diet without MT significantly increased from 10.33 to 14.00 and 14.33% after one week; 10.33 to15.33 and 15.00% after two weeks; 10.33 to 15.33 and 15.17% after three weeks and 10.33 to 15.83 and 16.83% after four weeks. But, supplementation of O. niloticus feed diet supplemented with MT and increasing rearing water temperature from to 30 or 35°C significantly increased mortality rate from 14.67 and 14.00% after one week; 16.00 and 15.67% after two weeks; 15.33 and 15.67% after three weeks and 16.00 and 17.33% after four weeks of treatment. The highest fry body weight was recorded for fry group administrated with MT and reared at water temperature of 35°C and the opposite trend was observed with fry group reared at the lower temperature (25°C) and fed diet without MT.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.