Prof. Magdy Abd El-Hamied Abdel-Rahman Soltan :: Publications:

Six ponds (2050 m2) were stocked by 1000 of Nile tilapia fingerlings for each pond. The six ponds assigned into two groups, each group composed of three ponds, the first pond stocked with the first stocking rate (SR1) of silver carp (100 fish/pond), the second pond stocked with the second stocking rate (SR2) of silver carp (200 fish/feddan) and the third pond of each group stocked with the third stocking rate (SR3) of silver carp (300 fish/pond). The three ponds of the first group had the first feeding treatment (fertilization with 50 kg poultry litter every week for each pond) and the three ponds of the second group had the second feeding treatment (fish feed containing 30% crude protein). Results obtained can be summarize as follows: - Means of body weights of Nile tilapia from the 4th week up to the 14th week of the experiment, fed the supplementary feed (containing 30% crude protein) were significantly higher than the same specie fed natural food enhanced by poultry litter as organic fertilization. Body weights of silver carp showed the opposite results. - Body weight of Nile tilapia increased with increasing silver carp stocking rate. Increasing silver carp stocking rate was followed by decrease in body weight of silver carp. - Using supplementary feed increased body length and body depth of Nile tilapia more than the other feeding treatment. The opposite trend was obtained with silver carp. - Condition factors for Nile tilapia and silver carp were paralleled with previous fish growth results. The effect of stocking rate on condition factor of Nile tilapia and silver carp are different within the whole period of the experiment. - The values of SGR of Nile tilapia from the first week up to 14th week of the experiment and within biweekly intervals, show that, using supplementary feed gave higher values than using poultry litter in most intervals. The opposite results was obtained with respect to silver carp. - The increasing stocking rate, SGR of Nile tilapia increased, while SGR of silver carp decreased. - The best SGR values for tilapia, due to the interaction between feeding treatment and stocking rate, were recorded with fish during the first four weeks as the rates ranged between 3.76-4.57 while in the rest weeks the rates ranged between 0.96-2.86. The best SGR values for silver carp were recorded with fish during the first eight weeks (0.37-1.83) while in the rest weeks the rates ranged between 0.38-1.13. - The total yield for Nile tilapia and silver carp at harvesting, after 14 weeks increased with each increase in stocking rate. In general the largest fish production (270 kg) for tilapia and silver carp was recorded from the pond had the supplementary feed and the third stocking rate (SR3), and the lowest fish yield (180 kg) obtained from the pond fertilized with poultry litter and had the first stocking rate (SR1).